QCW coil
Adam Munich, Wed Sept 28 2011, 10:05PMSo seeing as my x-ray machine requires only one 100ohm pot to be completed, I need another project. Now I was thinking about a 1'*4' DRSSTC to play my bass guitar through, and at first I was like: damn that's clunky...
BUT THEN, I came across steve ward's QCW coil.
=============================================== =====================================
Wow, that is quite amazing. That coil is about what, 1' tall and shoots out those huge lichenburg sparks?! I jelly, and in order to remedy this I must build one of those coils.
Does anyone happen to have any useful info those QCW coils?
[gren hopes this project won't take as long as his x-ray machine did]
Re: QCW coil
Dr. ISOTOP, Wed Sept 28 2011, 10:53PM
Ward's coil uses a modulated synchronous buck converter with 300A bricks as the power supply for a full bridge of minibricks (at least it did at one point, not sure what it uses now). Turns out if you feed a DRSSTC with a long triangular ramp, you can control the spark growth and get those long, straight sparks.
The design is pretty new, so there's not much info out there.
The hard part is the buck controller; regulating the pulse is not easy.
Dr. ISOTOP, Wed Sept 28 2011, 10:53PM
Ward's coil uses a modulated synchronous buck converter with 300A bricks as the power supply for a full bridge of minibricks (at least it did at one point, not sure what it uses now). Turns out if you feed a DRSSTC with a long triangular ramp, you can control the spark growth and get those long, straight sparks.
The design is pretty new, so there's not much info out there.
The hard part is the buck controller; regulating the pulse is not easy.
Re: QCW coil
magnet18, Thu Sept 29 2011, 01:41AM
Dawmn, That's impressive.
Has he posted a schematic anywhere?
I can't find one on google
magnet18, Thu Sept 29 2011, 01:41AM
Dawmn, That's impressive.
Has he posted a schematic anywhere?
I can't find one on google
Re: QCW coil
Weston, Thu Sept 29 2011, 04:10AM
Magnet18, Steve has not posted that much info about his QCW coil, and no schematic. From what I understand, this was to prevent the (often unaccredited) copying of his work.
Think of it as a challenge to design your own version. The concept is not that hard to understand. Sparks propagate differently depending on the rate of the rise in power. Steve has found a sweet spot where the sparks can propagate directly up and he can get large sparks from a small resonator without a fear of primary strikes.
Like bwang said, Steve uses a synchronous buck converter to directly modulate the buss voltage of a DRSSTC. He uses a primary with a relatively high impedance for a lower rise of current and to enable longer bursts. I believe his original coil had around a 300Khz secondary.
There is a thread which Steve started about his QCW coil that you should be able to find with the forum search. I also know Eric Goodchild was or is working on a QCW coil.
Weston, Thu Sept 29 2011, 04:10AM
Magnet18, Steve has not posted that much info about his QCW coil, and no schematic. From what I understand, this was to prevent the (often unaccredited) copying of his work.
Think of it as a challenge to design your own version. The concept is not that hard to understand. Sparks propagate differently depending on the rate of the rise in power. Steve has found a sweet spot where the sparks can propagate directly up and he can get large sparks from a small resonator without a fear of primary strikes.
Like bwang said, Steve uses a synchronous buck converter to directly modulate the buss voltage of a DRSSTC. He uses a primary with a relatively high impedance for a lower rise of current and to enable longer bursts. I believe his original coil had around a 300Khz secondary.
There is a thread which Steve started about his QCW coil that you should be able to find with the forum search. I also know Eric Goodchild was or is working on a QCW coil.
Re: QCW coil
Dr. Dark Current, Thu Sept 29 2011, 09:25AM
An idea for a "QCW-like" coil using standard parts, non-DR version:
-Build a standard SSTC with the 4046 as the oscillator and run the bridge from smoothed dc supply.
-Modulate the VCO on the upper slope of the resonance curve (above resonant frequency).
-Certain waveform inputs to the VCO should produce a QCW-like effect, as the VCO frequency is indirectly regulating output power. Try falling ramp waveforms in the several ms to a few tens of ms range, with variable slope.
I wanted to try this idea but it seems like it's never gonna happen, so I post it here for you to experiment. If you succeed it would be nice to hear about your results.
Dr. Dark Current, Thu Sept 29 2011, 09:25AM
An idea for a "QCW-like" coil using standard parts, non-DR version:
-Build a standard SSTC with the 4046 as the oscillator and run the bridge from smoothed dc supply.
-Modulate the VCO on the upper slope of the resonance curve (above resonant frequency).
-Certain waveform inputs to the VCO should produce a QCW-like effect, as the VCO frequency is indirectly regulating output power. Try falling ramp waveforms in the several ms to a few tens of ms range, with variable slope.
I wanted to try this idea but it seems like it's never gonna happen, so I post it here for you to experiment. If you succeed it would be nice to hear about your results.
Re: QCW coil
Adam Munich, Thu Sept 29 2011, 10:55AM
"Magnet18, Steve has not posted that much info about his QCW coil, and no schematic. From what I understand, this was to prevent the (often unaccredited) copying of his work."
It's a bad idea to not share your discoveries, for if you don't --they disappear with you.
-------------------------------------------- -------------------------------------------------- --------------------------------------------------
Drivers aside, it seems like the most logical way to start would be to make that short secondary. From the looks of it in the video, it seems to be 1 foot * 5 inches.
Here is some useful info I found on some other thread:
So, the coil is 9" tall, runs at 350khz and uses a 4CX250B in series with the bus to modulate it? It seems like the most logical option now would be to build a 350khz coil of similar dimensions...
Adam Munich, Thu Sept 29 2011, 10:55AM
"Magnet18, Steve has not posted that much info about his QCW coil, and no schematic. From what I understand, this was to prevent the (often unaccredited) copying of his work."
It's a bad idea to not share your discoveries, for if you don't --they disappear with you.
-------------------------------------------- -------------------------------------------------- --------------------------------------------------
Drivers aside, it seems like the most logical way to start would be to make that short secondary. From the looks of it in the video, it seems to be 1 foot * 5 inches.
Here is some useful info I found on some other thread:
So, the coil is 9" tall, runs at 350khz and uses a 4CX250B in series with the bus to modulate it? It seems like the most logical option now would be to build a 350khz coil of similar dimensions...
Re: QCW coil
Goodchild, Thu Sept 29 2011, 03:50PM
If you are interested my web site has a couple schematics for QCW modulators I have tried including the one that I finally got working perfectly. A link to my site is at the bottom of my post. The schematics on my site are not direct copyable, you do have to do some research for them to make sense and be buildable.
The QCW needs 3 things to make it work properly:
1: A resonant frequency of 350KHz or more! This is important as the lower you go in frequency the more your sparks are going to branch.
2: A method of modulating the output power so to "ramp" the power into the spark, this is what is used to control the spark growth. the dp/dt determines also how the spark branching will be effected. A larger dp/dt with result in more branching were a smaller dp/dt will result in less branching. This figure has to be adjusted also for the length of sparks you are producing. a longer spark needs a smaller dp/dt.
3: You need a high impedance tank circuit say >20ohm this is also to help control current rise times with the extremely long on time.
This type of coil run in basically the same mode as a VTTC only the tube is replaced with a bridge of IGBTs and the mot/cap is replaced with a class D amp. The advantage to having a controllable modulator is that unlike a VTTC you are not limited to the length of the mains AC for your ramp time. As I said before this length of time is critical when making sparks and at 33 or so inches VTTCs max out because they have no more ramp to work with.
I did spend a great deal of time and silicon to get this to work right, it's not a project for beginners or even moderate coil builders. You should have a good knowledge of SMPS control theory and power electronics if you want to attempt this project.
Goodchild, Thu Sept 29 2011, 03:50PM
If you are interested my web site has a couple schematics for QCW modulators I have tried including the one that I finally got working perfectly. A link to my site is at the bottom of my post. The schematics on my site are not direct copyable, you do have to do some research for them to make sense and be buildable.
The QCW needs 3 things to make it work properly:
1: A resonant frequency of 350KHz or more! This is important as the lower you go in frequency the more your sparks are going to branch.
2: A method of modulating the output power so to "ramp" the power into the spark, this is what is used to control the spark growth. the dp/dt determines also how the spark branching will be effected. A larger dp/dt with result in more branching were a smaller dp/dt will result in less branching. This figure has to be adjusted also for the length of sparks you are producing. a longer spark needs a smaller dp/dt.
3: You need a high impedance tank circuit say >20ohm this is also to help control current rise times with the extremely long on time.
This type of coil run in basically the same mode as a VTTC only the tube is replaced with a bridge of IGBTs and the mot/cap is replaced with a class D amp. The advantage to having a controllable modulator is that unlike a VTTC you are not limited to the length of the mains AC for your ramp time. As I said before this length of time is critical when making sparks and at 33 or so inches VTTCs max out because they have no more ramp to work with.
I did spend a great deal of time and silicon to get this to work right, it's not a project for beginners or even moderate coil builders. You should have a good knowledge of SMPS control theory and power electronics if you want to attempt this project.
Re: QCW coil
ScotchTapeLord, Thu Sept 29 2011, 04:12PM
It's not so much a discovery as a creation. Material creations can succeed their creators regardless of whether or not people know about them.
One of the big issues here is the power supply and its controller, where shielding and protective circuits are crucial to the design's success. I had the pleasure of working with Steve a couple weeks ago, and his power circuitry is far beyond hobbyist grade, with regard to the components, layout, and mechanical structures (heatsinks and enclosure). Even with all that, it still suffered a pretty severe meltdown.
There is no tube. Linear regulation of the supply is out of the question for any appreciable amount of power. You need a synchronous buck for best results. It works the same way as a class D audio amplifier, essentially.
ScotchTapeLord, Thu Sept 29 2011, 04:12PM
Grenadier wrote ...
It's a bad idea to not share your discoveries, for if you don't --they disappear with you.
It's a bad idea to not share your discoveries, for if you don't --they disappear with you.
It's not so much a discovery as a creation. Material creations can succeed their creators regardless of whether or not people know about them.
One of the big issues here is the power supply and its controller, where shielding and protective circuits are crucial to the design's success. I had the pleasure of working with Steve a couple weeks ago, and his power circuitry is far beyond hobbyist grade, with regard to the components, layout, and mechanical structures (heatsinks and enclosure). Even with all that, it still suffered a pretty severe meltdown.
Grenadier wrote ...
So, the coil is 9" tall, runs at 350khz and uses a 4CX250B in series with the bus to modulate it? It seems like the most logical option now would be to build a 350khz coil of similar dimensions...
So, the coil is 9" tall, runs at 350khz and uses a 4CX250B in series with the bus to modulate it? It seems like the most logical option now would be to build a 350khz coil of similar dimensions...
There is no tube. Linear regulation of the supply is out of the question for any appreciable amount of power. You need a synchronous buck for best results. It works the same way as a class D audio amplifier, essentially.
Re: QCW coil
Adam Munich, Thu Sept 29 2011, 05:14PM
Limited to the AC cycle time in a VTTC...
So if I'm understanding correctly, this is a solid state DC coil which operates in the mode of a VTTC. Wouldn't it be possible to rectify and smooth a VTTC to achieve the same effect? With a big enough bus cap, you should have enough stored energy in there to power the long resonations...
"It works the same way as a class D audio amplifier, essentially."
Not necessarily. Have we forgotten about the magnetic amplifier?
Adam Munich, Thu Sept 29 2011, 05:14PM
Limited to the AC cycle time in a VTTC...
So if I'm understanding correctly, this is a solid state DC coil which operates in the mode of a VTTC. Wouldn't it be possible to rectify and smooth a VTTC to achieve the same effect? With a big enough bus cap, you should have enough stored energy in there to power the long resonations...
"It works the same way as a class D audio amplifier, essentially."
Not necessarily. Have we forgotten about the magnetic amplifier?
Re: QCW coil
Dr. Drone, Thu Sept 29 2011, 05:49PM
Dr. Drone, Thu Sept 29 2011, 05:49PM
Re: QCW coil
Adam Munich, Thu Sept 29 2011, 07:23PM
I have two paper mica caps, .5uF at 1kV but those likely will not work. Maybe a MMC of "regular" silver mica caps like these could work. It'd certainly be cheaper/easier to obtain.
What I currently have;
* Plenty of 24, 25, 26 and 28 AWG wire
* Two dead XRTs, could be used to supply 600VAC if 1200 turns were piled on their big cores.
* Alu wire for making a toroid
* Maybe some other stuff
I am thinking about using vacuum tubes instead of IGBTs for this coil. Not only would a VT bridge be awesome looking, but it would also be a lot tougher to kill than expensive IGBTs. Of course high impedance might be a problem, but one can always just crank up the bus voltage.
A high voltage GDT would need to be made, but that's not exactly a tough thing to do.
Adam Munich, Thu Sept 29 2011, 07:23PM
I have two paper mica caps, .5uF at 1kV but those likely will not work. Maybe a MMC of "regular" silver mica caps like these could work. It'd certainly be cheaper/easier to obtain.
What I currently have;
* Plenty of 24, 25, 26 and 28 AWG wire
* Two dead XRTs, could be used to supply 600VAC if 1200 turns were piled on their big cores.
* Alu wire for making a toroid
* Maybe some other stuff
I am thinking about using vacuum tubes instead of IGBTs for this coil. Not only would a VT bridge be awesome looking, but it would also be a lot tougher to kill than expensive IGBTs. Of course high impedance might be a problem, but one can always just crank up the bus voltage.
A high voltage GDT would need to be made, but that's not exactly a tough thing to do.
Re: QCW coil
ScotchTapeLord, Thu Sept 29 2011, 08:28PM
I was just talking about the bus supply synchronous buck when I mentioned the class D amplifier, not anything having to do with the coil or its 350kHz H-bridge.
Careful modulation of the bus supply is what sets the QCW apart, and the power supply much more critical than in a standard SSTC. The actual part that supplies the primary with its power would typically be a standard H-bridge capable of withstanding the power dissipation associated with those long on times.
I have seen standard tube coils with very similar effects to the QCW, but the QCW's bus supply scheme allows you to fine tune the effects so you can get longer spark length for a given power input, swordier or branchier streamers, etc.
ScotchTapeLord, Thu Sept 29 2011, 08:28PM
I was just talking about the bus supply synchronous buck when I mentioned the class D amplifier, not anything having to do with the coil or its 350kHz H-bridge.
Careful modulation of the bus supply is what sets the QCW apart, and the power supply much more critical than in a standard SSTC. The actual part that supplies the primary with its power would typically be a standard H-bridge capable of withstanding the power dissipation associated with those long on times.
I have seen standard tube coils with very similar effects to the QCW, but the QCW's bus supply scheme allows you to fine tune the effects so you can get longer spark length for a given power input, swordier or branchier streamers, etc.
Re: QCW coil
Goodchild, Thu Sept 29 2011, 08:54PM
Ummm so your going to build a VTTC? A VTTC runs in the same mode but as said before what sets the QCW apart is being able to have longer ramp so that you can push more spark out of the system.
A VTTC is also a high impedance tank circuit and Dual Resonant. If you are interested in making a VTTC with a modulated bus supply you should talk to Phillip Slawinski over at Tesla Universe. He converted his 833C VTTC to what he calls a SSVC (Solid State Valve Coil). He also uses a solid state supply that puts a ramp onto the plate of the tube, but instead of a 0 to 300VDC ramp like the QCW, he uses a 0 to 20Kv ramp from what I understand, so that it is suitable for tube use.
From what he has told me and other over at TU the SSVC is even more expensive to construct than a QCW for a similar spark output. When you get right down to the nuts and bolts the operation mode is the same among VTTC QCW and SSVC, the differences comes from implementation. Each variant has it's advantages and disadvantages that must be considered when designing something like this.
Goodchild, Thu Sept 29 2011, 08:54PM
Grenadier wrote ...
I have two paper mica caps, .5uF at 1kV but those likely will not work. Maybe a MMC of "regular" silver mica caps like these could work. It'd certainly be cheaper/easier to obtain.
What I currently have;
* Plenty of 24, 25, 26 and 28 AWG wire
* Two dead XRTs, could be used to supply 600VAC if 1200 turns were piled on their big cores.
* Alu wire for making a toroid
* Maybe some other stuff
I am thinking about using vacuum tubes instead of IGBTs for this coil. Not only would a VT bridge be awesome looking, but it would also be a lot tougher to kill than expensive IGBTs. Of course high impedance might be a problem, but one can always just crank up the bus voltage.
A high voltage GDT would need to be made, but that's not exactly a tough thing to do.
I have two paper mica caps, .5uF at 1kV but those likely will not work. Maybe a MMC of "regular" silver mica caps like these could work. It'd certainly be cheaper/easier to obtain.
What I currently have;
* Plenty of 24, 25, 26 and 28 AWG wire
* Two dead XRTs, could be used to supply 600VAC if 1200 turns were piled on their big cores.
* Alu wire for making a toroid
* Maybe some other stuff
I am thinking about using vacuum tubes instead of IGBTs for this coil. Not only would a VT bridge be awesome looking, but it would also be a lot tougher to kill than expensive IGBTs. Of course high impedance might be a problem, but one can always just crank up the bus voltage.
A high voltage GDT would need to be made, but that's not exactly a tough thing to do.
Ummm so your going to build a VTTC? A VTTC runs in the same mode but as said before what sets the QCW apart is being able to have longer ramp so that you can push more spark out of the system.
A VTTC is also a high impedance tank circuit and Dual Resonant. If you are interested in making a VTTC with a modulated bus supply you should talk to Phillip Slawinski over at Tesla Universe. He converted his 833C VTTC to what he calls a SSVC (Solid State Valve Coil). He also uses a solid state supply that puts a ramp onto the plate of the tube, but instead of a 0 to 300VDC ramp like the QCW, he uses a 0 to 20Kv ramp from what I understand, so that it is suitable for tube use.
From what he has told me and other over at TU the SSVC is even more expensive to construct than a QCW for a similar spark output. When you get right down to the nuts and bolts the operation mode is the same among VTTC QCW and SSVC, the differences comes from implementation. Each variant has it's advantages and disadvantages that must be considered when designing something like this.
Re: QCW coil
Dr. Dark Current, Thu Sept 29 2011, 09:19PM
What about running a standard SSTC on half wave doubled voltage, similar to VTTC supply? Would this give longer sparks?
Dr. Dark Current, Thu Sept 29 2011, 09:19PM
What about running a standard SSTC on half wave doubled voltage, similar to VTTC supply? Would this give longer sparks?
Re: QCW coil
Goodchild, Thu Sept 29 2011, 09:22PM
Yes it would to some extent, but because it's not a dual resonant system, you will be hard pressed to get much more than 2 feet out of a normal SSTC with a reasonable input power.
Goodchild, Thu Sept 29 2011, 09:22PM
Dr. Kilovolt wrote ...
What about running a standard SSTC on half wave doubled voltage, similar to VTTC supply? Would this give longer sparks?
What about running a standard SSTC on half wave doubled voltage, similar to VTTC supply? Would this give longer sparks?
Yes it would to some extent, but because it's not a dual resonant system, you will be hard pressed to get much more than 2 feet out of a normal SSTC with a reasonable input power.
Re: QCW coil
Adam Munich, Thu Sept 29 2011, 09:57PM
From what I'm understanding, the only thing special about a qcw coil is the ramped bus supply.
People seem to be using class D amps to change the voltage. But since the transistors are not part of the resonant tan, and do not see the huge tank currents, you do not need expensive IGBTs to make the bus supply? If that is the case, yay.
What /me needs is a 15ms 100 to 600V ramp. Now I've got to figure out how to make it...
Adam Munich, Thu Sept 29 2011, 09:57PM
From what I'm understanding, the only thing special about a qcw coil is the ramped bus supply.
People seem to be using class D amps to change the voltage. But since the transistors are not part of the resonant tan, and do not see the huge tank currents, you do not need expensive IGBTs to make the bus supply? If that is the case, yay.
What /me needs is a 15ms 100 to 600V ramp. Now I've got to figure out how to make it...
Re: QCW coil
Goodchild, Thu Sept 29 2011, 10:24PM
They are subject to huge tank currents!! :P The current flowing through the IGBTs in regular DR where do you think it's pulling that current from? Thin air? No, the bus capacitor. But in a QCW, because the bus is modulated there is no tank cap on the main bridge and you pull your large current out of the class D amp. So your class D IGBTs and the filter inductor have to be able to handle the same peak current you plan to run in your tank.
The IGBTs in the H bridge for the coil see currents in the 100A to 200A peak range, much lower than a regular DR but for much longer periods of time (10mS to 20mS) so thermal dissipation becomes a very large factor as well.
Goodchild, Thu Sept 29 2011, 10:24PM
Grenadier wrote ...
From what I'm understanding, the only thing special about a qcw coil is the ramped bus supply.
People seem to be using class D amps to change the voltage. But since the transistors are not part of the resonant tan, and do not see the huge tank currents, you do not need expensive IGBTs to make the bus supply? If that is the case, yay.
What /me needs is a 15ms 100 to 600V ramp. Now I've got to figure out how to make it...
From what I'm understanding, the only thing special about a qcw coil is the ramped bus supply.
People seem to be using class D amps to change the voltage. But since the transistors are not part of the resonant tan, and do not see the huge tank currents, you do not need expensive IGBTs to make the bus supply? If that is the case, yay.
What /me needs is a 15ms 100 to 600V ramp. Now I've got to figure out how to make it...
They are subject to huge tank currents!! :P The current flowing through the IGBTs in regular DR where do you think it's pulling that current from? Thin air? No, the bus capacitor. But in a QCW, because the bus is modulated there is no tank cap on the main bridge and you pull your large current out of the class D amp. So your class D IGBTs and the filter inductor have to be able to handle the same peak current you plan to run in your tank.
The IGBTs in the H bridge for the coil see currents in the 100A to 200A peak range, much lower than a regular DR but for much longer periods of time (10mS to 20mS) so thermal dissipation becomes a very large factor as well.
Re: QCW coil
Adam Munich, Thu Sept 29 2011, 11:09PM
True...
Basically my goal is to get the biggest musical sparks out of the smallest possible coil (I want to replicate the first video). So it looks like the first step is to build the DRSTTC. I've never built one before, so I really have no clue what I'm doing :p
I get how it works. Basically you turn on the bridge, then turn it off before the IGBTs explode. But a qcw would run for 15ms, and that is a hell of a lot of cycles. That means that current must be controlled via the bus ramp?
I don't want to explode expensive parts, so I'm trying to figure all of this out. Speaking of exploding parts, what is the best DRSSTC driver for this system? I could design one, but since this is my first experience with all of this I'd prefer to not make my silicon go boom...
Adam Munich, Thu Sept 29 2011, 11:09PM
True...
Basically my goal is to get the biggest musical sparks out of the smallest possible coil (I want to replicate the first video). So it looks like the first step is to build the DRSTTC. I've never built one before, so I really have no clue what I'm doing :p
I get how it works. Basically you turn on the bridge, then turn it off before the IGBTs explode. But a qcw would run for 15ms, and that is a hell of a lot of cycles. That means that current must be controlled via the bus ramp?
I don't want to explode expensive parts, so I'm trying to figure all of this out. Speaking of exploding parts, what is the best DRSSTC driver for this system? I could design one, but since this is my first experience with all of this I'd prefer to not make my silicon go boom...
Re: QCW coil
Dr. ISOTOP, Thu Sept 29 2011, 11:20PM
The hard part of the coil is the sync buck powering it; the DRSSTC is just a standard DRSSTC.
Dr. ISOTOP, Thu Sept 29 2011, 11:20PM
Grenadier wrote ...
True...
Basically my goal is to get the biggest musical sparks out of the smallest possible coil (I want to replicate the first video). So it looks like the first step is to build the DRSTTC. I've never built one before, so I really have no clue what I'm doing :p
I get how it works. Basically you turn on the bridge, then turn it off before the IGBTs explode. But a qcw would run for 15ms, and that is a hell of a lot of cycles. That means that current must be controlled via the bus ramp?
I don't want to explode expensive parts, so I'm trying to figure all of this out. Speaking of exploding parts, what is the best DRSSTC driver for this system? I could design one, but since this is my first experience with all of this I'd prefer to not make my silicon go boom...
On a QCW, you control the primary current using a high-impedance tank circuit.True...
Basically my goal is to get the biggest musical sparks out of the smallest possible coil (I want to replicate the first video). So it looks like the first step is to build the DRSTTC. I've never built one before, so I really have no clue what I'm doing :p
I get how it works. Basically you turn on the bridge, then turn it off before the IGBTs explode. But a qcw would run for 15ms, and that is a hell of a lot of cycles. That means that current must be controlled via the bus ramp?
I don't want to explode expensive parts, so I'm trying to figure all of this out. Speaking of exploding parts, what is the best DRSSTC driver for this system? I could design one, but since this is my first experience with all of this I'd prefer to not make my silicon go boom...
The hard part of the coil is the sync buck powering it; the DRSSTC is just a standard DRSSTC.
Re: QCW coil
Adam Munich, Thu Sept 29 2011, 11:33PM
Assuming a 20uH primary and a f=350khz, I'd need a 10nF tank cap and the impedance would be 50 ohms. I'm not sure if I'd call that high...
As for the buck, hell not sure where to begin there. I happen to have a pair of these that could probably be used. Only 600V though, so the bus can't exceed 440V if there is a safety margin :-/ Also have 8 of these which I could //
Wish I had some sort of block diagram of the huge buck to look at.
Adam Munich, Thu Sept 29 2011, 11:33PM
Assuming a 20uH primary and a f=350khz, I'd need a 10nF tank cap and the impedance would be 50 ohms. I'm not sure if I'd call that high...
As for the buck, hell not sure where to begin there. I happen to have a pair of these
that could probably be used. Only 600V though, so the bus can't exceed 440V if there is a safety margin :-/ Also have 8 of these which I could // Wish I had some sort of block diagram of the huge buck to look at.
Re: QCW coil
Goodchild, Thu Sept 29 2011, 11:41PM
Ummm... I would start with a plain DRSSTC first before you go attempting a QCW. The QCW is about 10 magnitudes harder to build than a regular DRSSTC.
If I were you these are the steps I would take to get to a QCW:
1: Build and perfect a regular DRSSTC using Steve Ward's UD1.3b or 2.1b learn the ins and outs of a DRSSTC how to tune one tweak ect..
2: Build the class D / sync buck, get it working with static resistive loads at first and make sure you can make clean ripple free ramps.
3:Build a high impedance DRSSTC and bridge to go with the QCW and mate it with the sync buck.
4: Play with the sparks!
There's a big difference to knowing how something is going to work and making it work! In my experience with electronics and solid state tesla coils, you can't rush learning. You have to take small steps to achieve your overall goal.
So start with a plain DRSSTC first learn the lay of the land with this type of coil before attempting something like a QCW. By doing so you will save yourself a lot of headaches, money, and time.
Goodchild, Thu Sept 29 2011, 11:41PM
Ummm... I would start with a plain DRSSTC first before you go attempting a QCW. The QCW is about 10 magnitudes harder to build than a regular DRSSTC.
If I were you these are the steps I would take to get to a QCW:
1: Build and perfect a regular DRSSTC using Steve Ward's UD1.3b or 2.1b learn the ins and outs of a DRSSTC how to tune one tweak ect..
2: Build the class D / sync buck, get it working with static resistive loads at first and make sure you can make clean ripple free ramps.
3:Build a high impedance DRSSTC and bridge to go with the QCW and mate it with the sync buck.
4: Play with the sparks!
There's a big difference to knowing how something is going to work and making it work! In my experience with electronics and solid state tesla coils, you can't rush learning. You have to take small steps to achieve your overall goal.
So start with a plain DRSSTC first learn the lay of the land with this type of coil before attempting something like a QCW. By doing so you will save yourself a lot of headaches, money, and time.
Re: QCW coil
Adam Munich, Thu Sept 29 2011, 11:54PM
/me tends to do things the hard way.
Maybe an SSVC is the way to go. I want something that likely will not explode if I screw up, because when things explode I tend to abandon the project for months and it takes a long time to get anything done. Sure an SSVC would probably be a bit tougher, but in the end more reliable.
So, basically that is a DC VTTC with the bus voltage adjusted? Even then, how does one even make a 5-20kV ramp?
Adam Munich, Thu Sept 29 2011, 11:54PM
/me tends to do things the hard way.
Maybe an SSVC is the way to go. I want something that likely will not explode if I screw up, because when things explode I tend to abandon the project for months and it takes a long time to get anything done. Sure an SSVC would probably be a bit tougher, but in the end more reliable.
So, basically that is a DC VTTC with the bus voltage adjusted? Even then, how does one even make a 5-20kV ramp?
Re: QCW coil
Adam Munich, Fri Sept 30 2011, 01:21AM
Alright, it is now decided: this will be an SSVC coil. Why? Can't explode & glowy tubes are awesome.
So this video seems to be the only source of information on these coils.
What I gathered from the video is:
* The tesla coil is a standard VTCC, run on DC.
* He uses a pair of CM200 IGBTs to drive a transformer wound on two of those big TSC cores. I happen to have one, and it should be enough (2 seems overkill).
* The bus caps are 450V, so he is likely supplying the CM200s with 220 - 300V.
* There is a big capacitor in series with the transformer's primary to cancel inductance or something
* The transformer is doubled by MOCs and a big stack of to-220 diodes
* It makes a ramp
* The CM200s are driven by an arduino, simple enough
* The ramp peaks at 20kV and runs for about 15ms
All and all it doesn't look all that complicated. The question though is, how do I get a ramp out of a transformer like that? It was suggested that I lay a wooden plank atop a pole pig, but I have my doubts as to whether that is a good method...
How I will audio modulate this remains unknown. Maybe if I set the pulse length short enough I can just send pulses to the coil to directly make the sound. Frequency will of course be limited to the low end, but that's aright since I'd be using this for bass anyway.
Adam Munich, Fri Sept 30 2011, 01:21AM
Alright, it is now decided: this will be an SSVC coil. Why? Can't explode & glowy tubes are awesome.
So this video
seems to be the only source of information on these coils. What I gathered from the video is:
* The tesla coil is a standard VTCC, run on DC.
* He uses a pair of CM200 IGBTs to drive a transformer wound on two of those big TSC cores. I happen to have one, and it should be enough (2 seems overkill).
* The bus caps are 450V, so he is likely supplying the CM200s with 220 - 300V.
* There is a big capacitor in series with the transformer's primary to cancel inductance or something
* The transformer is doubled by MOCs and a big stack of to-220 diodes
* It makes a ramp
* The CM200s are driven by an arduino, simple enough
* The ramp peaks at 20kV and runs for about 15ms
All and all it doesn't look all that complicated. The question though is, how do I get a ramp out of a transformer like that? It was suggested that I lay a wooden plank atop a pole pig, but I have my doubts as to whether that is a good method...
How I will audio modulate this remains unknown. Maybe if I set the pulse length short enough I can just send pulses to the coil to directly make the sound. Frequency will of course be limited to the low end, but that's aright since I'd be using this for bass anyway.
Re: QCW coil
Dr. ISOTOP, Fri Sept 30 2011, 02:43AM
The "SSVC" is just as bad...you still have to deal with a pulsed, regulated, modulated DC-DC converter which drives an ill-behaved load (the coil itself). Plus you'll have to deal with winding a stable, high-power 10KV transformer
I'll reiterate - the hard part of this coil is the modulator, not the coil. A small DRSSTC is not terribly hard...lots of people have done it before, and there are people in the community who can help you. The pulsed class-D amp, however, is an odd beast. Try to build one, and you're venturing into fairly new territory. It is not clear what the best way to regulate the ramp is, or whether the class-D amp is even necessary at all (there are several people out there who are trying to integrate the ramp into the coil driver logic via techniques like pulse-skipping [see the "PSQCW coil" thread in the Projects subforum]).
Dr. ISOTOP, Fri Sept 30 2011, 02:43AM
The "SSVC" is just as bad...you still have to deal with a pulsed, regulated, modulated DC-DC converter which drives an ill-behaved load (the coil itself). Plus you'll have to deal with winding a stable, high-power 10KV transformer
I'll reiterate - the hard part of this coil is the modulator, not the coil. A small DRSSTC is not terribly hard...lots of people have done it before, and there are people in the community who can help you. The pulsed class-D amp, however, is an odd beast. Try to build one, and you're venturing into fairly new territory. It is not clear what the best way to regulate the ramp is, or whether the class-D amp is even necessary at all (there are several people out there who are trying to integrate the ramp into the coil driver logic via techniques like pulse-skipping [see the "PSQCW coil" thread in the Projects subforum]).
Re: QCW coil
Adam Munich, Fri Sept 30 2011, 03:20AM
Yeah... but tubes glow
Winding transformers isn't hard, the fryback is still alive and kicking so it can be done without oil. Plus this TSC core needs a job, and @ 20V/turn I'll need only 1000 turns to make 20kV (10kV == 500T).
Adam Munich, Fri Sept 30 2011, 03:20AM
Yeah... but tubes glow
Winding transformers isn't hard, the fryback is still alive and kicking so it can be done without oil. Plus this TSC core needs a job, and @ 20V/turn I'll need only 1000 turns to make 20kV (10kV == 500T).
Re: QCW coil
Phillip Slawinski, Fri Sept 30 2011, 03:43AM
WRONG!!!! Can explode ...........
Not that complicated? Yeah sure! It was easy... the thing practically built itself!
(if only)
Maybe one U core would be enough. You have to wind more primary turns (to avoid saturating the cores), and this means more secondary turns for the same voltage output. More secondary turns means smaller wire. The wire I have now is #24, and that's a bit small for even 600W output. The windings get quite warm. So if you go with one core, you're going to want to up the frequency so you can use fewer turns. This will limit the peak power output of the system, but if you're only planning to run something like an 833C then, no big deal. The 833C really starts to complain over 600W of power input.
I didn't use the TSC cores you speak of. I got them from another source, they may be similar to the TSC cores though?
The 450V rating is for one cap. I have two, and they're wired in series. I've run up to 800V on this power supply. Normally I run ~400V, since that's about all I need to max out the 833C. This supply was designed to run a bigger coil. I recently acquired a 3CX2500H3, but I haven't had the time to put that into a new coil yet.
The capacitor is in series with the primary it resonates with the leakage inductance of the primary, and also serves as a DC blocking cap.
Yep, MOCs and TO-220 diodes, I don't remember the exact model. I got some that were rated for 1200V @ ~30A. The diodes see pretty high peak current off the transformer.
Yep, it sure does. Very observant...
Sorta ... Maybe you can do it with the Arduino framework; I didn't use the Arduino framework. I wrote the controller in ASM. I only used that Mega because it was the only spare µC I had at the time.
20kV is the peak that the ANODE (on the tube) sees. I've taken the supply up to 12KV before, but at that point I feared for my Tube's life, so I backed down. You'll note if you look at the 833C datasheet that 20kV is WAAAAAY over spec. The tube I have installed is the only one I've seen that's able to handle that kind of abuse. (I've tried a few others)
The bottom line: SSVC isn't *easy*, I wouldn't recommend it as a beginner project.
I must give Credit where credit is due: I got some help from Steve Ward during the concept stage of the SSVC, so I can't take full credit for the SSVC. Steve gave me the idea to use a modulated SLR supply.
I haven't even finished this project, so I don't have any schematics or something like that to give away ( Not that I'd give it away anyway). I do have a few boards left, but I'm reluctant to sell them, the price would have to be right....
Phillip Slawinski, Fri Sept 30 2011, 03:43AM
Grenadier wrote ...
Alright, it is now decided: this will be an SSVC coil. Why? Can't explode & glowy tubes are awesome.
Alright, it is now decided: this will be an SSVC coil. Why? Can't explode & glowy tubes are awesome.
WRONG!!!! Can explode ...........
Grenadier wrote ...
All and all it doesn't look all that complicated.
All and all it doesn't look all that complicated.
Not that complicated? Yeah sure! It was easy... the thing practically built itself!
(if only)Grenadier wrote ...
* He uses a pair of CM200 IGBTs to drive a transformer wound on two of those big TSC cores. I happen to have one, and it should be enough (2 seems overkill).
* He uses a pair of CM200 IGBTs to drive a transformer wound on two of those big TSC cores. I happen to have one, and it should be enough (2 seems overkill).
Maybe one U core would be enough. You have to wind more primary turns (to avoid saturating the cores), and this means more secondary turns for the same voltage output. More secondary turns means smaller wire. The wire I have now is #24, and that's a bit small for even 600W output. The windings get quite warm. So if you go with one core, you're going to want to up the frequency so you can use fewer turns. This will limit the peak power output of the system, but if you're only planning to run something like an 833C then, no big deal. The 833C really starts to complain over 600W of power input.
I didn't use the TSC cores you speak of. I got them from another source, they may be similar to the TSC cores though?
Grenadier wrote ...
* The bus caps are 450V, so he is likely supplying the CM200s with 220 - 300V.
* The bus caps are 450V, so he is likely supplying the CM200s with 220 - 300V.
The 450V rating is for one cap. I have two, and they're wired in series. I've run up to 800V on this power supply. Normally I run ~400V, since that's about all I need to max out the 833C. This supply was designed to run a bigger coil. I recently acquired a 3CX2500H3, but I haven't had the time to put that into a new coil yet.
Grenadier wrote ...
* There is a big capacitor in series with the transformer's primary to cancel inductance or something
* There is a big capacitor in series with the transformer's primary to cancel inductance or something
The capacitor is in series with the primary it resonates with the leakage inductance of the primary, and also serves as a DC blocking cap.
Grenadier wrote ...
* The transformer is doubled by MOCs and a big stack of to-220 diodes
* The transformer is doubled by MOCs and a big stack of to-220 diodes
Yep, MOCs and TO-220 diodes, I don't remember the exact model. I got some that were rated for 1200V @ ~30A. The diodes see pretty high peak current off the transformer.
Grenadier wrote ...
* It makes a ramp
* It makes a ramp
Yep, it sure does. Very observant...
Grenadier wrote ...
* The CM200s are driven by an arduino, simple enough
* The CM200s are driven by an arduino, simple enough
Sorta ... Maybe you can do it with the Arduino framework; I didn't use the Arduino framework. I wrote the controller in ASM. I only used that Mega because it was the only spare µC I had at the time.
Grenadier wrote ...
* The ramp peaks at 20kV and runs for about 15ms
* The ramp peaks at 20kV and runs for about 15ms
20kV is the peak that the ANODE (on the tube) sees. I've taken the supply up to 12KV before, but at that point I feared for my Tube's life, so I backed down. You'll note if you look at the 833C datasheet that 20kV is WAAAAAY over spec. The tube I have installed is the only one I've seen that's able to handle that kind of abuse. (I've tried a few others)
The bottom line: SSVC isn't *easy*, I wouldn't recommend it as a beginner project.
I must give Credit where credit is due: I got some help from Steve Ward during the concept stage of the SSVC, so I can't take full credit for the SSVC. Steve gave me the idea to use a modulated SLR supply.
I haven't even finished this project, so I don't have any schematics or something like that to give away ( Not that I'd give it away anyway). I do have a few boards left, but I'm reluctant to sell them, the price would have to be right....
Re: QCW coil
Adam Munich, Fri Sept 30 2011, 03:53AM
I'm just wondering *how* you got the ramp waveform out of the transformer, since I really haven't a clue!
As for the cores, it's a big one that can handle on average 35V/T before saturating. 20V gives me a decent safety margin.
I don't really plan on running it over 600W. Just enough to give me a decent bass amp. As for the "not recommend as a beginner project" part, I certainly don't recommend you make your first x-ray machine play nice with micro controllers and powered off of LiPos
But I'm not one to turn down a challenge, and this is a challenge indeed.
Adam Munich, Fri Sept 30 2011, 03:53AM
I'm just wondering *how* you got the ramp waveform out of the transformer, since I really haven't a clue!
As for the cores, it's a big one that can handle on average 35V/T before saturating. 20V gives me a decent safety margin.
I don't really plan on running it over 600W. Just enough to give me a decent bass amp. As for the "not recommend as a beginner project" part, I certainly don't recommend you make your first x-ray machine play nice with micro controllers and powered off of LiPos
But I'm not one to turn down a challenge, and this is a challenge indeed.
Re: QCW coil
Dr. ISOTOP, Fri Sept 30 2011, 06:07AM
I've always wondered, how are you modulating the SLR? AFAIK PWM would throw off the resonance condition (the duty cycle would be limited to fo, 1/2fo, 1/3fo, etc to maintain ZCS).
Dr. ISOTOP, Fri Sept 30 2011, 06:07AM
Phillip Slawinski wrote ...
I must give Credit where credit is due: I got some help from Steve Ward during the concept stage of the SSVC, so I can't take full credit for the SSVC. Steve gave me the idea to use a modulated SLR supply.
I haven't even finished this project, so I don't have any schematics or something like that to give away ( Not that I'd give it away anyway). I do have a few boards left, but I'm reluctant to sell them, the price would have to be right....
I must give Credit where credit is due: I got some help from Steve Ward during the concept stage of the SSVC, so I can't take full credit for the SSVC. Steve gave me the idea to use a modulated SLR supply.
I haven't even finished this project, so I don't have any schematics or something like that to give away ( Not that I'd give it away anyway). I do have a few boards left, but I'm reluctant to sell them, the price would have to be right....
I've always wondered, how are you modulating the SLR? AFAIK PWM would throw off the resonance condition (the duty cycle would be limited to fo, 1/2fo, 1/3fo, etc to maintain ZCS).
Re: QCW coil
Phillip Slawinski, Fri Sept 30 2011, 12:58PM
Winding transformers isn't difficult, but be sure you have a good design. The design of the transformer will determine the performance you can get from the system. The transformer I have in my supply now leaves something to be desired, which is why I redesigned it, and had custom bobbins made. You probably won't need to go to that length.
You want the coupling on the transformer as tight as possible. This means it's important to have the windings coaxial. The lower the leakage inductance is, the larger resonant cap you can use. Also you can get away with running a higher frequency for a given power output, this means you can use fewer primary turns, and thus fewer secondary turns for a given output voltage. Another added benefit of the higher modulation frequency is tighter regulation.
1000 turns, wow. What kind of wire size would you plan to use for this? I use #24, in a single layer that spans a little less than the length of the winding window. When I'm running around 300-400W input into the SLR the windings seem to stabilize at around 160ºF - 190ºF or so, which is quite warm.
Did you account for using a doubler when you made your turns calculations above? The doubler isn't there to just give more voltage, it also serves the crucial functions of rectifying and filtering the output. I should note that the doubler was one of the most expensive parts, if not the most expensive part of the project. This is because the diodes not only need to be high voltage but high current as well. They see pretty high peak currents. From the simulation I recall the peak currents being 30 amps or so. The good news is that the diodes don't see much current at turn off thanks to the whole ZCS thing. You may be able to get away with smaller diodes, and bring the cost down. I designed this supply to run a much larger coil than it's presently running, so it's quite overbuilt for running an 833C coil.
35V / Turn at what frequency?
I'm running about 100V / turn on my transformer. My switching frequency is around 60kHz The primary is four or five turns (can't remember).
If you plan to play music that changes things. Music is generally more power hungry than just making long sword sparks at a few PPS. That 600W figure I threw out is what I use to make 60" sword sparks at about 1PPS. Audio of any kind is going to use more power if you want decent volume out of the coil. If you want CW audio modulation, then I wouldn't recommend a single phase SLR. The bandwidth is pretty low unless you add more phases, or use a pretty high switching frequency.
Originally I implemented this with a transformer isolated buck supply. I wasn't able to get the performance I wanted with that, but then I didn't pursue it very long before switching to modulated SLR. I think the SLR is a much nicer topology anyways because it is *automagically* protected from shorts on the output. A fixed amount of energy is allowed to pass through the system on each cycle, no matter what the load is. This has come in handy more than once. Originally this 833C coil was a traditional VTTC with MOTs.
When I hooked this to the modulator I forgot to remove the doubler diode (which was rated at 10kV). At some point I exceeded 10kV on the B+, and the diode went out with a bang. This left a short from B+ to ground, when this happened the power consumption of the modulator went down rather than going up, and nothing was broken in the modulator.
The SLR operates with 1/2 wave pulses, just like any other SLR supply. An unmodulated SLR has a duty cycle of 50%. (A output on 1/2 cycle, Off 1/2 Cycle, B on 1/2 cycle) The modulation is achieved by varying the length of the off time. This modulates the duty cycle, but does not change the on time for each pulse.
Phillip Slawinski, Fri Sept 30 2011, 12:58PM
Grenadier wrote ...
Winding transformers isn't hard, the fryback is still alive and kicking so it can be done without oil. Plus this TSC core needs a job, and @ 20V/turn I'll need only 1000 turns to make 20kV (10kV == 500T).
Winding transformers isn't hard, the fryback is still alive and kicking so it can be done without oil. Plus this TSC core needs a job, and @ 20V/turn I'll need only 1000 turns to make 20kV (10kV == 500T).
Winding transformers isn't difficult, but be sure you have a good design. The design of the transformer will determine the performance you can get from the system. The transformer I have in my supply now leaves something to be desired, which is why I redesigned it, and had custom bobbins made. You probably won't need to go to that length.
You want the coupling on the transformer as tight as possible. This means it's important to have the windings coaxial. The lower the leakage inductance is, the larger resonant cap you can use. Also you can get away with running a higher frequency for a given power output, this means you can use fewer primary turns, and thus fewer secondary turns for a given output voltage. Another added benefit of the higher modulation frequency is tighter regulation.
1000 turns, wow. What kind of wire size would you plan to use for this? I use #24, in a single layer that spans a little less than the length of the winding window. When I'm running around 300-400W input into the SLR the windings seem to stabilize at around 160ºF - 190ºF or so, which is quite warm.
Did you account for using a doubler when you made your turns calculations above? The doubler isn't there to just give more voltage, it also serves the crucial functions of rectifying and filtering the output. I should note that the doubler was one of the most expensive parts, if not the most expensive part of the project. This is because the diodes not only need to be high voltage but high current as well. They see pretty high peak currents. From the simulation I recall the peak currents being 30 amps or so. The good news is that the diodes don't see much current at turn off thanks to the whole ZCS thing. You may be able to get away with smaller diodes, and bring the cost down. I designed this supply to run a much larger coil than it's presently running, so it's quite overbuilt for running an 833C coil.
Grenadier wrote ...
As for the cores, it's a big one that can handle on average 35V/T before saturating. 20V gives me a decent safety margin.
As for the cores, it's a big one that can handle on average 35V/T before saturating. 20V gives me a decent safety margin.
35V / Turn at what frequency?
I'm running about 100V / turn on my transformer. My switching frequency is around 60kHz The primary is four or five turns (can't remember).
Grenadier wrote ...
I don't really plan on running it over 600W. Just enough to give me a decent bass amp.
I don't really plan on running it over 600W. Just enough to give me a decent bass amp.
If you plan to play music that changes things. Music is generally more power hungry than just making long sword sparks at a few PPS. That 600W figure I threw out is what I use to make 60" sword sparks at about 1PPS. Audio of any kind is going to use more power if you want decent volume out of the coil. If you want CW audio modulation, then I wouldn't recommend a single phase SLR. The bandwidth is pretty low unless you add more phases, or use a pretty high switching frequency.
Originally I implemented this with a transformer isolated buck supply. I wasn't able to get the performance I wanted with that, but then I didn't pursue it very long before switching to modulated SLR. I think the SLR is a much nicer topology anyways because it is *automagically* protected from shorts on the output. A fixed amount of energy is allowed to pass through the system on each cycle, no matter what the load is. This has come in handy more than once. Originally this 833C coil was a traditional VTTC with MOTs.
When I hooked this to the modulator I forgot to remove the doubler diode (which was rated at 10kV). At some point I exceeded 10kV on the B+, and the diode went out with a bang. This left a short from B+ to ground, when this happened the power consumption of the modulator went down rather than going up, and nothing was broken in the modulator. bwang wrote ...
I've always wondered, how are you modulating the SLR? AFAIK PWM would throw off the resonance condition (the duty cycle would be limited to fo, 1/2fo, 1/3fo, etc to maintain ZCS).
I've always wondered, how are you modulating the SLR? AFAIK PWM would throw off the resonance condition (the duty cycle would be limited to fo, 1/2fo, 1/3fo, etc to maintain ZCS).
The SLR operates with 1/2 wave pulses, just like any other SLR supply. An unmodulated SLR has a duty cycle of 50%. (A output on 1/2 cycle, Off 1/2 Cycle, B on 1/2 cycle) The modulation is achieved by varying the length of the off time. This modulates the duty cycle, but does not change the on time for each pulse.
Re: QCW coil
Adam Munich, Fri Sept 30 2011, 01:16PM
I didn't account for the doubler..., so yes I'd need only 500T (but likely less, being conservative here). I figured the doubler provides a some sort of special function aside from doubling...
The SLR supply: I take it that each pulse you get out of the system == 1 SLR cycle to the transformer? That doesn't sound right, because you'd need huge peak currents to get anything out of it.
If that is not the case and the transformer is powered continuously, then how do you manage to get a ramp out of that CW?
Bandwidth isn't much of an issue. A 5ms pulse == a max pulse freq of 200Hz, which is fine for bass guitar. Power might be a problem; though that's what bigger parts are for once you get something working.
Adam Munich, Fri Sept 30 2011, 01:16PM
I didn't account for the doubler..., so yes I'd need only 500T (but likely less, being conservative here). I figured the doubler provides a some sort of special function aside from doubling...
The SLR supply: I take it that each pulse you get out of the system == 1 SLR cycle to the transformer? That doesn't sound right, because you'd need huge peak currents to get anything out of it.
If that is not the case and the transformer is powered continuously, then how do you manage to get a ramp out of that CW?
Bandwidth isn't much of an issue. A 5ms pulse == a max pulse freq of 200Hz, which is fine for bass guitar. Power might be a problem; though that's what bigger parts are for once you get something working.
Re: QCW coil
Phillip Slawinski, Fri Sept 30 2011, 01:55PM
The peak currents are pretty massive. I've measured 400A on the primary side before.
If you aren't familiar with SLR I'd suggest reading up on it. The only major difference between this and an unmodulated supply is that I vary off time between alternating pulses on the bridge to achieve modulation.
You're not always switching at the maximum switching frequency, especially during the start of a ramp. Depending on your design you can actually end up with the SLR modulating the pulse rate down to the audible range. If you have inadequate filtering this will be audible.
If you want to just make ramps to simulate the sound, maybe through MIDI or something you should be okay. If you want to plug a guitar into it and play it while the coil is running essentially CW, you will probably have issues.
You might consider using a transformer isolated buck. That's what I started with. All you have to do is take a buck mode supply and slap a transformer on the output. This will provide better modulation if you want to do analog audio modulation.
Phillip Slawinski, Fri Sept 30 2011, 01:55PM
Grenadier wrote ...
The SLR supply: I take it that each pulse you get out of the system == 1 SLR cycle to the transformer? That doesn't sound right, because you'd need huge peak currents to get anything out of it.
The SLR supply: I take it that each pulse you get out of the system == 1 SLR cycle to the transformer? That doesn't sound right, because you'd need huge peak currents to get anything out of it.
The peak currents are pretty massive. I've measured 400A on the primary side before.
If you aren't familiar with SLR I'd suggest reading up on it. The only major difference between this and an unmodulated supply is that I vary off time between alternating pulses on the bridge to achieve modulation.
Grenadier wrote ...
Bandwidth isn't much of an issue. A 5ms pulse == a max pulse freq of 200Hz, which is fine for bass guitar. Power might be a problem; though that's what bigger parts are for once you get something working.
Bandwidth isn't much of an issue. A 5ms pulse == a max pulse freq of 200Hz, which is fine for bass guitar. Power might be a problem; though that's what bigger parts are for once you get something working.
You're not always switching at the maximum switching frequency, especially during the start of a ramp. Depending on your design you can actually end up with the SLR modulating the pulse rate down to the audible range. If you have inadequate filtering this will be audible.
If you want to just make ramps to simulate the sound, maybe through MIDI or something you should be okay. If you want to plug a guitar into it and play it while the coil is running essentially CW, you will probably have issues.
You might consider using a transformer isolated buck. That's what I started with. All you have to do is take a buck mode supply and slap a transformer on the output. This will provide better modulation if you want to do analog audio modulation.
Re: QCW coil
Adam Munich, Mon Oct 03 2011, 01:12AM
Alright, so if I am understanding correctly, you are varying the power and thus output voltage by increasing the spacing between cycles?
That doesn't seem right; seems like it'd toss the entire thing out of resonance!
From what I'm reading it seems like changing loads on the transformer don't significantly affect the resonant frequency, and thus I could just use a uC to set the timing and be done with it. But I still feel that I'm getting something wrong here, since spacing in between those cycles... doesn't seem right.
EDIT: fixed stupid mistake
Adam Munich, Mon Oct 03 2011, 01:12AM
Alright, so if I am understanding correctly, you are varying the power and thus output voltage by increasing the spacing between cycles?
That doesn't seem right; seems like it'd toss the entire thing out of resonance!
From what I'm reading
it seems like changing loads on the transformer don't significantly affect the resonant frequency, and thus I could just use a uC to set the timing and be done with it. But I still feel that I'm getting something wrong here, since spacing in between those cycles... doesn't seem right.EDIT: fixed stupid mistake
Re: QCW coil
ScotchTapeLord, Mon Oct 03 2011, 01:19AM
I believe that spacing is what prevents resonant rise, it gives time for the resonant tank to dump its stored energy back into the supply. I'm not entirely sure if that is right, but if you ran it at resonance it would ring up like a DRSSTC tank, whereas you want control over the output for this application (whereas, with a DRSSTC, out of control currents running away is desirable).
ScotchTapeLord, Mon Oct 03 2011, 01:19AM
I believe that spacing is what prevents resonant rise, it gives time for the resonant tank to dump its stored energy back into the supply. I'm not entirely sure if that is right, but if you ran it at resonance it would ring up like a DRSSTC tank, whereas you want control over the output for this application (whereas, with a DRSSTC, out of control currents running away is desirable).
Re: QCW coil
Adam Munich, Wed Nov 16 2011, 05:17AM
Well guys, I finally have a pair of 4-1000As.
But now I think going the silicon route would be better These things get smoking hot just running the heater, and a fan really would kill some of the awesomeness factor. I think I might keep these, or one tube to build a 1000W transmitter some time in the future to troll the fcc ...play with.
So, I'm going to build Steve Ward's DRSSTC driver Start there, because I'm still at a loss on how to make a ramp supply for the coil, and I managed to find four 72A G27N120BN IGBTs. Used to have more but I've got no clue where they went off to.
Adam Munich, Wed Nov 16 2011, 05:17AM
Well guys, I finally have a pair of 4-1000As.
But now I think going the silicon route would be better
These things get smoking hot just running the heater, and a fan really would kill some of the awesomeness factor. I think I might keep these, or one tube to build a 1000W transmitter some time in the future to troll the fcc ...play with. So, I'm going to build Steve Ward's DRSSTC driver
Start there, because I'm still at a loss on how to make a ramp supply for the coil, and I managed to find four 72A G27N120BN IGBTs. Used to have more but I've got no clue where they went off to.Re: QCW coil
Marko, Wed Nov 16 2011, 05:27AM
Hi grenadier
Well, there's a russian guy on this site who has built some epic pulsed tube coils... just copying some of his designs might be a very fun start! (not sure what is the pulse rating of those tubes you have though...) I'd love to see something novel such as a coil base fed by a half bridge of tubes or something like that.
Apart from that, you should perhaps look at the thread named 'CWDRSSTC' for the newest development on the QCW coils, and within short time me or Steve Conner will attempt to reach it using delta sigma modulation technique which might even be appliable for VTTC's without the massive external SLR supply!
You will need some big energy discharge caps no matter what though :)
Marko
Marko, Wed Nov 16 2011, 05:27AM
Hi grenadier
Well, there's a russian guy on this site who has built some epic pulsed tube coils... just copying some of his designs might be a very fun start! (not sure what is the pulse rating of those tubes you have though...) I'd love to see something novel such as a coil base fed by a half bridge of tubes or something like that.
Apart from that, you should perhaps look at the thread named 'CWDRSSTC' for the newest development on the QCW coils, and within short time me or Steve Conner will attempt to reach it using delta sigma modulation technique which might even be appliable for VTTC's without the massive external SLR supply!
You will need some big energy discharge caps no matter what though :)
Marko
Re: QCW coil
Adam Munich, Wed Nov 16 2011, 05:38AM
I don't know the pulse rating, but they make special 4-1000As that are designed for pulses. Problem is those cost about $600 each...
I happen to have 40 doorknob caps coming in the mail via an impulse buy. $2.99 each for some very high DV/DT 30kV 780pf doorknobs, but even all of them in // would only give me 31nf so they are unsuitable for a silicon DRSSTC. They might work for a tube coil, but they are very nice EMP caps. 1.2 megavolts in a coaxial marx... (no clue how to build one though)
Usually these things go for about $20-$30 each
I don't know... If I go the tube route then I'll need to design a special cooling system and figure out a way to supply the 6000V for the plates, but I don't have a suitable tank cap for a silicon DRSSTC. Quite a pickle isn't it?
Adam Munich, Wed Nov 16 2011, 05:38AM
I don't know the pulse rating, but they make special 4-1000As that are designed for pulses. Problem is those cost about $600 each...
I happen to have 40 doorknob caps coming in the mail via an impulse buy. $2.99 each for some very high DV/DT 30kV 780pf doorknobs, but even all of them in // would only give me 31nf so they are unsuitable for a silicon DRSSTC. They might work for a tube coil, but they are very nice EMP caps. 1.2 megavolts in a coaxial marx... (no clue how to build one though)
Usually these things go for about $20-$30 each I don't know... If I go the tube route then I'll need to design a special cooling system and figure out a way to supply the 6000V for the plates, but I don't have a suitable tank cap for a silicon DRSSTC. Quite a pickle isn't it?
Re: QCW coil
Marko, Wed Nov 16 2011, 05:53AM
Hi - well do you have any MOT's around? Two MOT's + FWR could do a power supply provided you have a big enough energy storage cap... (have any?)
Marko
Marko, Wed Nov 16 2011, 05:53AM
Hi - well do you have any MOT's around? Two MOT's + FWR could do a power supply provided you have a big enough energy storage cap... (have any?)
Marko
Re: QCW coil
Adam Munich, Wed Nov 16 2011, 11:35AM
I don't have to idenical, or even two similar ones. I have two 9kV 60mA NSTs and maybe 4 30mA ones... maybe if I centertap rectify them and put them in a bus I could get something worthwhile, but now weight is starting to be a concern. :-/
Adam Munich, Wed Nov 16 2011, 11:35AM
I don't have to idenical, or even two similar ones. I have two 9kV 60mA NSTs and maybe 4 30mA ones... maybe if I centertap rectify them and put them in a bus I could get something worthwhile, but now weight is starting to be a concern. :-/
Re: QCW coil
Marko, Wed Nov 16 2011, 01:08PM
Hi,
Well, if you have a big pulse cap for your power supply, you can still charge it relatively slowly using your NST ... a MOT stack will get heavy as well, and not to talk about other components of the tube coil!
Marko
Marko, Wed Nov 16 2011, 01:08PM
Hi,
Well, if you have a big pulse cap for your power supply, you can still charge it relatively slowly using your NST ... a MOT stack will get heavy as well, and not to talk about other components of the tube coil!
Marko
Re: QCW coil
Adam Munich, Wed Nov 16 2011, 01:32PM
I don't have any pulse caps though. Just a whole bunch of lytics that are capable of exploding things.
Hrm. I think I might just go the silicon route, though I'm going to have a tough time finding caps suitable for the tank.
Adam Munich, Wed Nov 16 2011, 01:32PM
I don't have any pulse caps though. Just a whole bunch of lytics that are capable of exploding things.
Hrm. I think I might just go the silicon route, though I'm going to have a tough time finding caps suitable for the tank.
Re: QCW coil
Marko, Wed Nov 16 2011, 01:40PM
Hi grenadier,
Some 50 - 100 of these should make a great QCW tank cap, just leave some to other people too!
Marko
Marko, Wed Nov 16 2011, 01:40PM
Hi grenadier,
Some 50 - 100 of these should make a great QCW tank cap, just leave some to other people too!
Marko
Re: QCW coil
Adam Munich, Wed Nov 16 2011, 02:28PM
Good find! I hope they don't explode though, from what I've heard those fancy CDE caps are the only ones good for DRSSTC work...
Adam Munich, Wed Nov 16 2011, 02:28PM
Good find! I hope they don't explode though, from what I've heard those fancy CDE caps are the only ones good for DRSSTC work...
Re: QCW coil
Mads Barnkob, Wed Nov 16 2011, 03:37PM
Not quite right :)
Mads Barnkob, Wed Nov 16 2011, 03:37PM
Grenadier wrote ...
Good find! I hope they don't explode though, from what I've heard those fancy CDE caps are the only ones good for DRSSTC work...
Good find! I hope they don't explode though, from what I've heard those fancy CDE caps are the only ones good for DRSSTC work...
Not quite right :)
Re: QCW coil
Dr. ISOTOP, Wed Nov 16 2011, 03:40PM
QCW's have teeny tank caps, on the order of 20-ish nF.
What you really want in that application is a mica transmitting cap.
Dr. ISOTOP, Wed Nov 16 2011, 03:40PM
QCW's have teeny tank caps, on the order of 20-ish nF.
What you really want in that application is a mica transmitting cap.
Re: QCW coil
Marko, Wed Nov 16 2011, 04:23PM
These caps are MMKP and might be more prone to failing at the ends than FKP caps. Still, I believe they'll work for relatively low currents of the QCW :)
Marko
Marko, Wed Nov 16 2011, 04:23PM
These caps are MMKP and might be more prone to failing at the ends than FKP caps. Still, I believe they'll work for relatively low currents of the QCW :)
Marko
Re: QCW coil
Adam Munich, Wed Nov 16 2011, 04:59PM
Well I was first going to get this thing working as a regular DRSSTC, then figure out how to make it QCW. Kinda hoping that I'd be able to witch between the two, so yeah I'd need to find some beefy caps for the tank.
Adam Munich, Wed Nov 16 2011, 04:59PM
Well I was first going to get this thing working as a regular DRSSTC, then figure out how to make it QCW. Kinda hoping that I'd be able to witch between the two, so yeah I'd need to find some beefy caps for the tank.
Re: QCW coil
teravolt, Thu Nov 17 2011, 04:52AM
Hi Grenadier I am workinig on gatering up the parts for QCW and I am working on the converter first. I am hopping on geting some input from others because I have some of thease russian doorknob caps that have a RF rating
your doorknob caps that you all ready have might be suitible. I considered taking a bunch and paralleling them on some aluminuim plates. the advantage is that the coil can be tuned by removing caps from a bank. The G27N120BN is a good choice, they are 500 watt devices.
teravolt, Thu Nov 17 2011, 04:52AM
Hi Grenadier I am workinig on gatering up the parts for QCW and I am working on the converter first. I am hopping on geting some input from others because I have some of thease russian doorknob caps that have a RF rating
your doorknob caps that you all ready have might be suitible. I considered taking a bunch and paralleling them on some aluminuim plates. the advantage is that the coil can be tuned by removing caps from a bank. The G27N120BN is a good choice, they are 500 watt devices.
Re: QCW coil
Marko, Thu Nov 17 2011, 06:51AM
The KVI 3 caps are lossy ceramic type, they are useless for anything but low frequencies and DC. The general rule is, if the cap doesn't have kVAR rating on it, it's probably not intended to run any reactive power at all.
Marko
Marko, Thu Nov 17 2011, 06:51AM
teravolt wrote ...
Hi Grenadier I am workinig on gatering up the parts for QCW and I am working on the converter first. I am hopping on geting some input from others because I have some of thease russian doorknob caps that have a RF rating
your doorknob caps that you all ready have might be suitible. I considered taking a bunch and paralleling them on some aluminuim plates. the advantage is that the coil can be tuned by removing caps from a bank. The G27N120BN is a good choice, they are 500 watt devices.
Hi Grenadier I am workinig on gatering up the parts for QCW and I am working on the converter first. I am hopping on geting some input from others because I have some of thease russian doorknob caps that have a RF rating
your doorknob caps that you all ready have might be suitible. I considered taking a bunch and paralleling them on some aluminuim plates. the advantage is that the coil can be tuned by removing caps from a bank. The G27N120BN is a good choice, they are 500 watt devices.
The KVI 3 caps are lossy ceramic type, they are useless for anything but low frequencies and DC. The general rule is, if the cap doesn't have kVAR rating on it, it's probably not intended to run any reactive power at all.
Marko
Re: QCW coil
teravolt, Thu Nov 17 2011, 02:45PM
Marko, I have seen pictures of thease caps as tank caps in rf tube amplifier equipment. they may not be as saperior as mica but I think thay will do at least for me. have you tried using them before.
teravolt, Thu Nov 17 2011, 02:45PM
Marko, I have seen pictures of thease caps as tank caps in rf tube amplifier equipment. they may not be as saperior as mica but I think thay will do at least for me. have you tried using them before.
Re: QCW coil
Mads Barnkob, Thu Nov 17 2011, 03:43PM
I have some smaller ones of the same type, here is the datasheet
Mads Barnkob, Thu Nov 17 2011, 03:43PM
Marko wrote ...
The KVI 3 caps are lossy ceramic type, they are useless for anything but low frequencies and DC. The general rule is, if the cap doesn't have kVAR rating on it, it's probably not intended to run any reactive power at all.
Marko
teravolt wrote ...
Hi Grenadier I am workinig on gatering up the parts for QCW and I am working on the converter first. I am hopping on geting some input from others because I have some of thease russian doorknob caps that have a RF rating
your doorknob caps that you all ready have might be suitible. I considered taking a bunch and paralleling them on some aluminuim plates. the advantage is that the coil can be tuned by removing caps from a bank. The G27N120BN is a good choice, they are 500 watt devices.
Hi Grenadier I am workinig on gatering up the parts for QCW and I am working on the converter first. I am hopping on geting some input from others because I have some of thease russian doorknob caps that have a RF rating
your doorknob caps that you all ready have might be suitible. I considered taking a bunch and paralleling them on some aluminuim plates. the advantage is that the coil can be tuned by removing caps from a bank. The G27N120BN is a good choice, they are 500 watt devices.
The KVI 3 caps are lossy ceramic type, they are useless for anything but low frequencies and DC. The general rule is, if the cap doesn't have kVAR rating on it, it's probably not intended to run any reactive power at all.
Marko
I have some smaller ones of the same type, here is the datasheet
CAPACITY: 470 pF (+20 -20 %)
TEST Voltage: 24.000 VDC
MAX. WORKING Voltage: 16.000 VDC
MAX. WORKING current at f=30MHz: 15A (200 A pulse)
Dissipation factor at f=30MHz: <0,002
Insulation resistance: >10000 MOhm
Temperature of work: -60* +120*C (-76 to 248F)
Dimensions: 25x16 mm (0,98"D x 0,63"high)
Mass: 45 gramm (1,6oz)
Re: QCW coil
Marko, Thu Nov 17 2011, 04:40PM
Yes,I've tried, and failed miserably, they are actually the same as those blue ceramic HV caps... tried running a parallel tank circuit with them at huge disappointment, even with no load the Q was so bad it couldn't get to oscillate. Apart from high losses those are also very temperature variant and also display high piezoelectricity.
How well would they be for a tube coil, well, after all I've seen people using glass bottle caps but what you're really after are RF rated strontium titanate caps (which you'll find to have usually more conservative voltage rating than KVI's) or just go for a MMC of polypropylene caps.
Marko
Marko, Thu Nov 17 2011, 04:40PM
teravolt wrote ...
Marko, I have seen pictures of thease caps as tank caps in rf tube amplifier equipment. they may not be as saperior as mica but I think thay will do at least for me. have you tried using them before.
Marko, I have seen pictures of thease caps as tank caps in rf tube amplifier equipment. they may not be as saperior as mica but I think thay will do at least for me. have you tried using them before.
Yes,I've tried, and failed miserably, they are actually the same as those blue ceramic HV caps... tried running a parallel tank circuit with them at huge disappointment, even with no load the Q was so bad it couldn't get to oscillate. Apart from high losses those are also very temperature variant and also display high piezoelectricity.
How well would they be for a tube coil, well, after all I've seen people using glass bottle caps but what you're really after are RF rated strontium titanate caps (which you'll find to have usually more conservative voltage rating than KVI's) or just go for a MMC of polypropylene caps.
Marko
Re: QCW coil
teravolt, Fri Nov 18 2011, 04:12AM
hmm ok so your saying only poly's and mica's are good for MMC? I would prefer a nice mika for a QCW that I am working on around 500khz and I could aford something in the 100$ right now if you had any suggestions I am open. I have a cuple dozen of the russian doorknobs that Mads desribes Above and for one of my tests I plan to mount about 15-20 of those caps to a cuple of aluiminuim plates for a mmc.
teravolt, Fri Nov 18 2011, 04:12AM
hmm ok so your saying only poly's and mica's are good for MMC? I would prefer a nice mika for a QCW that I am working on around 500khz and I could aford something in the 100$ right now if you had any suggestions I am open. I have a cuple dozen of the russian doorknobs that Mads desribes Above and for one of my tests I plan to mount about 15-20 of those caps to a cuple of aluiminuim plates for a mmc.
Re: QCW coil
Goodchild, Fri Nov 18 2011, 07:01AM
I would have to say MICA is by far the best choice for the QCW.
In my QCW I have tried poly,mica, and teflon. I will give a little insight on the three from my experiments.
The Teflon -> They work and they work HOT!!! They suck plain and simple... (but they do work... sorta...)
Poly -> Although they are great for high current pulsed applications like a regular DR they tend to get hot in the high RMS environment of the QCW. If you made an MMC you would need many caps in parallel for a good RMS rating. The plus side though is that because the peak current is low the voltage rating can also be very low, probably only two or three 2kv caps in series for the most applications.
MICA -> There awesome, most mica caps can have great RMS ratings and already have a nice high voltage rating. I use a single 10nF 10Kv MICA rated at 18Arms in my QCW and that thing don't break a sweat at 20pps 100Apk in the tank. I would highly suggest MICA for the QCW, that's if you can find them! hehe
Goodchild, Fri Nov 18 2011, 07:01AM
I would have to say MICA is by far the best choice for the QCW.
In my QCW I have tried poly,mica, and teflon. I will give a little insight on the three from my experiments.
The Teflon -> They work and they work HOT!!! They suck plain and simple... (but they do work... sorta...)
Poly -> Although they are great for high current pulsed applications like a regular DR they tend to get hot in the high RMS environment of the QCW. If you made an MMC you would need many caps in parallel for a good RMS rating. The plus side though is that because the peak current is low the voltage rating can also be very low, probably only two or three 2kv caps in series for the most applications.
MICA -> There awesome, most mica caps can have great RMS ratings and already have a nice high voltage rating. I use a single 10nF 10Kv MICA rated at 18Arms in my QCW and that thing don't break a sweat at 20pps 100Apk in the tank. I would highly suggest MICA for the QCW, that's if you can find them! hehe
Re: QCW coil
teravolt, Fri Nov 18 2011, 03:10PM
Goodchild I definatly agree, it sound like there aren't many substitutes. I have a bunch of those big old shool mica transmiting caps on hand and some small ones to for experimental purpace but they are not very portable. I could buy a new mica right now but there are others like Grenadier hear who might have to save a bit. unfortunatly a QCW is not a pore mans game. I am building the SLR right now like Phillip Slawinski but with a cuple of tweaks of my own. With the stuff on hand I have spent 150 just for the water cooling. like Grenadier I am lerning what to do next. so far I have one yay and one nay for russian doorknobs if you include Mads Barnkob. have you had any expirence with them? the reson I picked them is because of there low series inductance. According to Marko they have to much series resistance and get hot. I don't know if his application is the same as mine so I hope to try it and report.
teravolt, Fri Nov 18 2011, 03:10PM
Goodchild I definatly agree, it sound like there aren't many substitutes. I have a bunch of those big old shool mica transmiting caps on hand and some small ones to for experimental purpace but they are not very portable. I could buy a new mica right now but there are others like Grenadier hear who might have to save a bit. unfortunatly a QCW is not a pore mans game. I am building the SLR right now like Phillip Slawinski but with a cuple of tweaks of my own. With the stuff on hand I have spent 150 just for the water cooling. like Grenadier I am lerning what to do next. so far I have one yay and one nay for russian doorknobs if you include Mads Barnkob. have you had any expirence with them? the reson I picked them is because of there low series inductance. According to Marko they have to much series resistance and get hot. I don't know if his application is the same as mine so I hope to try it and report.
Re: QCW coil
Marko, Fri Nov 18 2011, 03:39PM
Hi guys,
Well I think russian doorknob caps are quite straight actually - they mostly look the same with the same green coating on them, but if they don't have a kVAR rating listed on them (such as the KVI3) they are the sucky type, while for example K15Y-1 look almost the same but have kVA rating on them.
There are also those tubular ceramic caps which have more surface area for cooling and better volume efficiency.
Still you will need quite a dozen of those to get the required capacitance as the biggest are 4.7nF or so.
It's somewhat bizzare that teflon caps end up being more lossy than mica counterparts, with mica being so much crappier dielectric than teflon. The teflon caps also seem very robustly constructed with whole aluminum foil electrodes.
On the other hand I've pushed 5 parallel strings of CDE caps to some 60-70A in CW and they didn't see even a tiny bit of heating (while the very wiring leading to them was actually getting hot!)
150nF CDE's would be too high capacitance for the purpose though; you would need some in 10-20nF range (group buy anyone?) to get enough parallel stacks.
Marko
Marko, Fri Nov 18 2011, 03:39PM
Hi guys,
Well I think russian doorknob caps are quite straight actually - they mostly look the same with the same green coating on them, but if they don't have a kVAR rating listed on them (such as the KVI3) they are the sucky type, while for example K15Y-1 look almost the same but have kVA rating on them.
There are also those tubular ceramic caps which have more surface area for cooling and better volume efficiency.
Still you will need quite a dozen of those to get the required capacitance as the biggest are 4.7nF or so.
It's somewhat bizzare that teflon caps end up being more lossy than mica counterparts, with mica being so much crappier dielectric than teflon. The teflon caps also seem very robustly constructed with whole aluminum foil electrodes.
On the other hand I've pushed 5 parallel strings of CDE caps to some 60-70A in CW and they didn't see even a tiny bit of heating (while the very wiring leading to them was actually getting hot!)
150nF CDE's would be too high capacitance for the purpose though; you would need some in 10-20nF range (group buy anyone?) to get enough parallel stacks.
Marko
Re: QCW coil
Dr. Dark Current, Fri Nov 18 2011, 03:45PM
A question for you guys: When the coil is supplied from a half wave recified unfiltered mains without any modulator circuits (such as in my case), is there any "sweet spot" for the running frequency at which I get the longest sparks for a given input power? I always thought that lower frequency = longer sparks, because lower frequency sparks are not as hot so they might grow longer to lenght. Or is this not true?
Edit: This question should have went into my "CWDRSSTC" thread, but I think here it is ok too
Dr. Dark Current, Fri Nov 18 2011, 03:45PM
A question for you guys: When the coil is supplied from a half wave recified unfiltered mains without any modulator circuits (such as in my case), is there any "sweet spot" for the running frequency at which I get the longest sparks for a given input power? I always thought that lower frequency = longer sparks, because lower frequency sparks are not as hot so they might grow longer to lenght. Or is this not true?
Edit: This question should have went into my "CWDRSSTC" thread, but I think here it is ok too
Re: QCW coil
Goodchild, Fri Nov 18 2011, 04:39PM
Well as I said before 300KHz+ is the best for making supper long strait sparks. Also if you could sync your interrupter to the mains voltage so the coil turns on right with the half wave pules it would operate in much similar way to the QCW using the half wave pulses as the bus modulation. This is very similar to how Steve Ward first experimented with the QCW.
Teravolt, I have not had a chance to work with the doorknob caps in my QCW so not sure if I can give any insight on them.
Goodchild, Fri Nov 18 2011, 04:39PM
Dr. Kilovolt wrote ...
A question for you guys: When the coil is supplied from a half wave recified unfiltered mains without any modulator circuits (such as in my case), is there any "sweet spot" for the running frequency at which I get the longest sparks for a given input power? I always thought that lower frequency = longer sparks, because lower frequency sparks are not as hot so they might grow longer to lenght. Or is this not true?
Edit: This question should have went into my "CWDRSSTC" thread, but I think here it is ok too
A question for you guys: When the coil is supplied from a half wave recified unfiltered mains without any modulator circuits (such as in my case), is there any "sweet spot" for the running frequency at which I get the longest sparks for a given input power? I always thought that lower frequency = longer sparks, because lower frequency sparks are not as hot so they might grow longer to lenght. Or is this not true?
Edit: This question should have went into my "CWDRSSTC" thread, but I think here it is ok too
Well as I said before 300KHz+ is the best for making supper long strait sparks. Also if you could sync your interrupter to the mains voltage so the coil turns on right with the half wave pules it would operate in much similar way to the QCW using the half wave pulses as the bus modulation. This is very similar to how Steve Ward first experimented with the QCW.
Teravolt, I have not had a chance to work with the doorknob caps in my QCW so not sure if I can give any insight on them.
Re: QCW coil
teravolt, Fri Nov 18 2011, 05:07PM
I think you asked about this before but I have seen teslas that use rectified AC that have sword sparks and weren't VTTC. from what I have seen it is a combination of things like a ramped type of wave and secondary frequency. I think that VTTCs use half of a ac sign wave wich is 8.3mS to build sparks where all this started. tubes and small fets are ideal because of there frequency range. I believe that sword sparks just look longer because they are sreight. the sweat spot for frequeny has been stated to be 350k to 500k. I wonder what the sparks look like above that.
teravolt, Fri Nov 18 2011, 05:07PM
I think you asked about this before but I have seen teslas that use rectified AC that have sword sparks and weren't VTTC. from what I have seen it is a combination of things like a ramped type of wave and secondary frequency. I think that VTTCs use half of a ac sign wave wich is 8.3mS to build sparks where all this started. tubes and small fets are ideal because of there frequency range. I believe that sword sparks just look longer because they are sreight. the sweat spot for frequeny has been stated to be 350k to 500k. I wonder what the sparks look like above that.
Re: QCW coil
Dr. Dark Current, Fri Nov 18 2011, 05:26PM
Do you think the optimal frequency depends on input (peak?) power and spark length? Common sense tells me that the optimal frequency would be lower for longer sparks with more input power, or am I wrong here?
Dr. Dark Current, Fri Nov 18 2011, 05:26PM
Do you think the optimal frequency depends on input (peak?) power and spark length? Common sense tells me that the optimal frequency would be lower for longer sparks with more input power, or am I wrong here?
Re: QCW coil
Herr Zapp, Sat Nov 19 2011, 06:24AM
Goodchild -
You mentioned that your QCW coil uses a single 10nF, 10kV mica capacitor. In the world of mica transmitting capacitors, .01uF at 10kV is a rather unusual rating, hinting at a physically very large capacitor.
Is this a G-series capacitor, with a cylindrical ceramic housing and cast aluminum end plates? Or a cylindrical CDE cap with cast-epoxy case? Or something else?
Can you post a photo of your cap?
Herr Zapp
Herr Zapp, Sat Nov 19 2011, 06:24AM
Goodchild -
You mentioned that your QCW coil uses a single 10nF, 10kV mica capacitor. In the world of mica transmitting capacitors, .01uF at 10kV is a rather unusual rating, hinting at a physically very large capacitor.
Is this a G-series capacitor, with a cylindrical ceramic housing and cast aluminum end plates? Or a cylindrical CDE cap with cast-epoxy case? Or something else?
Can you post a photo of your cap?
Herr Zapp
Re: QCW coil
Adam Munich, Mon Nov 21 2011, 10:44PM
Well, found me a pipe. How the hell this thing ended up 5 miles off a seasonal road in the middle of nowheresville,-79.115081&hl=en&ll=42.315813,-
79.124823&spn=0.009092,0.01929&sll=42.298192,-
79.115593&sspn=0.009094,0.01929&vpsrc=6&gl=us&t=h&
z=16 is beond me, but it's schedule 80 4", perfect for the coil.
And here's a 14 inch piece sanded to 250 grit and cut square on a bandsaw.
Now I need to do some winding. I have 24awg, 25awg, 26awg and 28awg. What do you think would be best if I was going for 350khz?
Adam Munich, Mon Nov 21 2011, 10:44PM
Well, found me a pipe. How the hell this thing ended up 5 miles off a seasonal road in the middle of nowheresville
,-79.115081&hl=en&ll=42.315813,-
79.124823&spn=0.009092,0.01929&sll=42.298192,-
79.115593&sspn=0.009094,0.01929&vpsrc=6&gl=us&t=h&
z=16 is beond me, but it's schedule 80 4", perfect for the coil.
And here's a 14 inch piece sanded to 250 grit and cut square on a bandsaw.
Now I need to do some winding. I have 24awg, 25awg, 26awg and 28awg. What do you think would be best if I was going for 350khz?
Re: QCW coil
Dr. Dark Current, Fri Nov 25 2011, 11:24PM
Guys, what peak powers are we talking about here? From what I've read, it seems we need around 10-20 kW peak for some 40" QCW sparks, does this sound about right?
Dr. Dark Current, Fri Nov 25 2011, 11:24PM
Guys, what peak powers are we talking about here? From what I've read, it seems we need around 10-20 kW peak for some 40" QCW sparks, does this sound about right?
Re: QCW coil
Goodchild, Sat Nov 26 2011, 07:24AM
Peak power for what the tank circuit or wall draw?
The peak power for each burst can be rather high, but draw from the wall can be considerably lower. I can get 40" with 800W if I only run 1 or 2 pps
Goodchild, Sat Nov 26 2011, 07:24AM
Dr. Kilovolt wrote ...
Guys, what peak powers are we talking about here? From what I've read, it seems we need around 10-20 kW peak for some 40" QCW sparks, does this sound about right?
Guys, what peak powers are we talking about here? From what I've read, it seems we need around 10-20 kW peak for some 40" QCW sparks, does this sound about right?
Peak power for what the tank circuit or wall draw?
The peak power for each burst can be rather high, but draw from the wall can be considerably lower. I can get 40" with 800W if I only run 1 or 2 pps
Re: QCW coil
Dr. Dark Current, Sat Nov 26 2011, 08:55AM
I meant for the bridge supply, what is the peak output power at the end of the burst.
Dr. Dark Current, Sat Nov 26 2011, 08:55AM
I meant for the bridge supply, what is the peak output power at the end of the burst.
Re: QCW coil
Goodchild, Sat Nov 26 2011, 04:44PM
Well that is the same as the tank current which is usually <100Apk. But this is why you use a large bucket cap on the modulator, so that it can supply those large currents for short periods of time.
All this info is on my QCW page
Goodchild, Sat Nov 26 2011, 04:44PM
Well that is the same as the tank current which is usually <100Apk. But this is why you use a large bucket cap on the modulator, so that it can supply those large currents for short periods of time.
All this info is on my QCW page
Re: QCW coil
teravolt, Sat Nov 26 2011, 06:05PM
knowing how much power is being transferred from your energy storage electrolytic to the spark its self is a complex equation. I cant imagine that a Tesla is more than 30% efficient with out mesuring. Goodchild have you ever used a person transformers to mesure the secondary current during a arc.
teravolt, Sat Nov 26 2011, 06:05PM
knowing how much power is being transferred from your energy storage electrolytic to the spark its self is a complex equation. I cant imagine that a Tesla is more than 30% efficient with out mesuring. Goodchild have you ever used a person transformers to mesure the secondary current during a arc.
Re: QCW coil
Steve Conner, Sat Nov 26 2011, 09:29PM
No it's not that hard. To a first approximation, take your DC bus voltage, multiply by 4/pi, divide by the square root of 2, multiply by your peak tank current (as measured by fiddling with the OCD, etc) then divide by root 2 again.
Or hook your digital scope up to the coil, multiply voltage and current together, integrate, divide by burst length.
Either way I get about 50kW burst power for my Mjollnir coil. (In its old configuration. I had to lower it for the QCW conversion to avoid overheating, it is now nearer 20kW.)
And from other measurements I know it is at least 65% efficient, not 30.
Steve Conner, Sat Nov 26 2011, 09:29PM
No it's not that hard. To a first approximation, take your DC bus voltage, multiply by 4/pi, divide by the square root of 2, multiply by your peak tank current (as measured by fiddling with the OCD, etc) then divide by root 2 again.
Or hook your digital scope up to the coil, multiply voltage and current together, integrate, divide by burst length.
Either way I get about 50kW burst power for my Mjollnir coil. (In its old configuration. I had to lower it for the QCW conversion to avoid overheating, it is now nearer 20kW.)
And from other measurements I know it is at least 65% efficient, not 30.
Re: QCW coil
Dr. Dark Current, Sat Nov 26 2011, 10:50PM
Thanks, just wanted to try this with a tube so I can design the tank circuit for the desired kW peak output. I think I'll go for some 12-15 kW and see if it's enough.
Dr. Dark Current, Sat Nov 26 2011, 10:50PM
Thanks, just wanted to try this with a tube so I can design the tank circuit for the desired kW peak output. I think I'll go for some 12-15 kW and see if it's enough.
Re: QCW coil
teravolt, Sun Nov 27 2011, 02:50AM
Hi Steve, is that for a coupling of about .2? the shape of your primary may have less or more transfer of energy depending on its shape and aproximation to the secondary. Steve Wards QCW's primary probly has a coupling of .4 or more. would it be pausible to use a signal generator, scope, and load to figure out the energy transfer for a specific coil?
teravolt, Sun Nov 27 2011, 02:50AM
Hi Steve, is that for a coupling of about .2? the shape of your primary may have less or more transfer of energy depending on its shape and aproximation to the secondary. Steve Wards QCW's primary probly has a coupling of .4 or more. would it be pausible to use a signal generator, scope, and load to figure out the energy transfer for a specific coil?
Re: QCW coil
Goodchild, Sun Nov 27 2011, 08:08AM
I find that a great way to approximate energy transfer is to simulate the coil. The tricky part is the spark loading, I have yet to come up with a decent spark loading model for the QCW. I have used the Terry spark model for DRSSTC in the past with good results, but I remembering Steve Ward saying something about having to modify the model to get accurate results for the QCW.
As for coupling, .4K is about as high as I go with my QCW. I usually run about 0.35k or 0.36k. I find that this coupling is rather important, really important actually to achieve straight sparks. If the coupling is to low you get sparks that look a lot like what you get out of a regular DR with long PW and if to high the system will flash over. Tuning also seems to have a heavy influence on this.
Goodchild, Sun Nov 27 2011, 08:08AM
I find that a great way to approximate energy transfer is to simulate the coil. The tricky part is the spark loading, I have yet to come up with a decent spark loading model for the QCW. I have used the Terry spark model for DRSSTC in the past with good results, but I remembering Steve Ward saying something about having to modify the model to get accurate results for the QCW.
As for coupling, .4K is about as high as I go with my QCW. I usually run about 0.35k or 0.36k. I find that this coupling is rather important, really important actually to achieve straight sparks. If the coupling is to low you get sparks that look a lot like what you get out of a regular DR with long PW and if to high the system will flash over. Tuning also seems to have a heavy influence on this.
Re: QCW coil
Dr. Drone, Sun Dec 04 2011, 01:22AM
Dr. Drone, Sun Dec 04 2011, 01:22AM
Re: QCW coil
Goodchild, Sun Dec 04 2011, 07:57AM
Strange, I seem to have a cap in my QCW that looks exactly like that.... I wonder how that happened....
Goodchild, Sun Dec 04 2011, 07:57AM
Dr. Spark wrote ...
Herr Zapp wrote ...
Goodchild -
You mentioned that your QCW coil uses a single 10nF, 10kV mica capacitor. In the world of mica transmitting capacitors, .01uF at 10kV is a rather unusual rating, hinting at a physically very large capacitor.
Is this a G-series capacitor, with a cylindrical ceramic housing and cast aluminum end plates? Or a cylindrical CDE cap with cast-epoxy case? Or something else?
Can you post a photo of your cap?
Here is what these juicy caps look like, a few ended up in Steve Ward’s QCW coil @
Cheers,
Mica Man!
Goodchild -
You mentioned that your QCW coil uses a single 10nF, 10kV mica capacitor. In the world of mica transmitting capacitors, .01uF at 10kV is a rather unusual rating, hinting at a physically very large capacitor.
Is this a G-series capacitor, with a cylindrical ceramic housing and cast aluminum end plates? Or a cylindrical CDE cap with cast-epoxy case? Or something else?
Can you post a photo of your cap?
Here is what these juicy caps look like, a few ended up in Steve Ward’s QCW coil @
Cheers,
Mica Man!
Strange, I seem to have a cap in my QCW that looks exactly like that.... I wonder how that happened....
Re: QCW coil
teravolt, Sun Dec 04 2011, 04:45PM
Hi Dr. Spark, are you sure those are mica caps for sure, they might be film caps? Not that that is a bad thing but I would like to know if a QCW could use a film or does it have to be RF rated? mica transmitting caps are generally RF rated, I believe because of there low dissipation factor. why not use Russian door knob caps. I have seen them in Rf amp tank circuits. I have received a couple of thumbs down for them. The caps in Dr. Spark's picture have a 100KHz rating so at a QCW frequency of 350 to 500KHz are they suitable because of the low QCW duty cycle?
teravolt, Sun Dec 04 2011, 04:45PM
Hi Dr. Spark, are you sure those are mica caps for sure, they might be film caps? Not that that is a bad thing but I would like to know if a QCW could use a film or does it have to be RF rated? mica transmitting caps are generally RF rated, I believe because of there low dissipation factor. why not use Russian door knob caps. I have seen them in Rf amp tank circuits. I have received a couple of thumbs down for them. The caps in Dr. Spark's picture have a 100KHz rating so at a QCW frequency of 350 to 500KHz are they suitable because of the low QCW duty cycle?
Re: QCW coil
Goodchild, Sun Dec 04 2011, 05:48PM
They are indeed MICA you can tell just by how heavy they are. A film cap would work but you wold need to make a MMC of it in order to get a suitable RMS rating. That MICA cap is an excellent QCW capacitor, as they will handle the high RMS ratings of a the QCW wich can be near CW. I bet a doorknob cap would work as well although you may need to make a MMC out it.
Just because the IGBTs 60N60s are rated at 60A that didn't stop anyone from running them at 600A pulsed.... Ratings are made to be broken
Goodchild, Sun Dec 04 2011, 05:48PM
They are indeed MICA you can tell just by how heavy they are. A film cap would work but you wold need to make a MMC of it in order to get a suitable RMS rating. That MICA cap is an excellent QCW capacitor, as they will handle the high RMS ratings of a the QCW wich can be near CW. I bet a doorknob cap would work as well although you may need to make a MMC out it.
The caps in Dr. Spark's picture have a 100KHz rating so at a QCW frequency of 350 to 500KHz are they suitable because of the low QCW duty cycle?
Just because the IGBTs 60N60s are rated at 60A that didn't stop anyone from running them at 600A pulsed.... Ratings are made to be broken
Re: QCW coil
Dr. Drone, Sun Dec 04 2011, 06:28PM
Dr. Drone, Sun Dec 04 2011, 06:28PM
Re: QCW coil
teravolt, Mon Dec 05 2011, 12:16AM
Thease are from russia with love. This will be a MMC hopfully they will work
teravolt, Mon Dec 05 2011, 12:16AM
Thease are from russia with love. This will be a MMC hopfully they will work
Re: QCW coil
Marko, Mon Dec 05 2011, 12:58AM
Hi teravolt,
Sorry to disappoint, but those all look like KVI-3 caps. I got fooled the same way - they're pretty useless for any useful reactive power handling. They are actually the same material and purpose as those blue drop HV ceramic caps, just in a fancier packaging...
I've found that general rule for russian caps is, if they don't have KVAR rating written on them, they aren't intended for it at all!
Marko
Marko, Mon Dec 05 2011, 12:58AM
Hi teravolt,
Sorry to disappoint, but those all look like KVI-3 caps. I got fooled the same way - they're pretty useless for any useful reactive power handling. They are actually the same material and purpose as those blue drop HV ceramic caps, just in a fancier packaging...
I've found that general rule for russian caps is, if they don't have KVAR rating written on them, they aren't intended for it at all!
Marko
Re: QCW coil
Goodchild, Mon Dec 05 2011, 07:40AM
I would much rather invest in MICA's then stocks right now Can I get the name of your MICA broker Dr. Spark?
Goodchild, Mon Dec 05 2011, 07:40AM
Dr. Spark wrote ...
Have had good luck with Strontium Titanate doorknob capacitors as abused them in the dual 833c VTTC and they never got hot @ , only issue is they are mucho $$$$$$. Have lots of flavors of doorknobs, some work well for RF and others get hot and are more designed for bypass caps. Issue is if they get hot, the value changes detuning your tank.
Have been collecting Mica’s as a hobby as they are getting harder to find and the prices are getting silly. They are very heavy caps but worth the weight indeed. Seeing the Sangamd caps used for over $250 each…that is just crazy. Guess Mica’s are a good investment hee hee.
Rgs,
Dr. Spark
Have had good luck with Strontium Titanate doorknob capacitors as abused them in the dual 833c VTTC and they never got hot @
, only issue is they are mucho $$$$$$. Have lots of flavors of doorknobs, some work well for RF and others get hot and are more designed for bypass caps. Issue is if they get hot, the value changes detuning your tank.Have been collecting Mica’s as a hobby as they are getting harder to find and the prices are getting silly. They are very heavy caps but worth the weight indeed. Seeing the Sangamd caps used for over $250 each…that is just crazy. Guess Mica’s are a good investment hee hee.
Rgs,
Dr. Spark
I would much rather invest in MICA's then stocks right now
Can I get the name of your MICA broker Dr. Spark?Re: QCW coil
RogerInOhio, Mon Dec 05 2011, 02:26PM
Teravolt, The Russian caps may not be the best but they work ok for me. Anything works better than vine bottle capacitors although I do miss the smell of ozone produced by the corona around the tops of the bottles.
RogerInOhio, Mon Dec 05 2011, 02:26PM
Teravolt, The Russian caps may not be the best but they work ok for me.
Anything works better than vine bottle capacitors although I do miss the smell of ozone produced by the corona around the tops of the bottles.Re: QCW coil
teravolt, Tue Dec 06 2011, 03:05AM
thanks for the encuragement RogerInOhio, I plan to use them in a pulsed duty application and I will derate them and see where it goes. I think they will do something. I have plenty of mica's to do what I want if they don't work
teravolt, Tue Dec 06 2011, 03:05AM
thanks for the encuragement RogerInOhio, I plan to use them in a pulsed duty application and I will derate them and see where it goes. I think they will do something. I have plenty of mica's to do what I want if they don't work
Re: QCW coil
Dr. Dark Current, Tue Dec 06 2011, 09:43AM
There are more types of the "russian caps". There are caps which are used for power HF oscillators, usually have kVARs printed on them, and those caps can take huge RF abuse.
Dr. Dark Current, Tue Dec 06 2011, 09:43AM
There are more types of the "russian caps". There are caps which are used for power HF oscillators, usually have kVARs printed on them, and those caps can take huge RF abuse.
Re: QCW coil
magnet18, Tue Dec 06 2011, 03:29PM
Where is that math derived from??
Is the derivative of spark length power?
I'm just curious
magnet18, Tue Dec 06 2011, 03:29PM
Dr. Quark wrote ...
No it's not that hard. To a first approximation, take your DC bus voltage, multiply by 4/pi, divide by the square root of 2, multiply by your peak tank current (as measured by fiddling with the OCD, etc) then divide by root 2 again.
Or hook your digital scope up to the coil, multiply voltage and current together, integrate, divide by burst length.
Either way I get about 50kW burst power for my Mjollnir coil. (In its old configuration. I had to lower it for the QCW conversion to avoid overheating, it is now nearer 20kW.)
And from other measurements I know it is at least 65% efficient, not 30.
No it's not that hard. To a first approximation, take your DC bus voltage, multiply by 4/pi, divide by the square root of 2, multiply by your peak tank current (as measured by fiddling with the OCD, etc) then divide by root 2 again.
Or hook your digital scope up to the coil, multiply voltage and current together, integrate, divide by burst length.
Either way I get about 50kW burst power for my Mjollnir coil. (In its old configuration. I had to lower it for the QCW conversion to avoid overheating, it is now nearer 20kW.)
And from other measurements I know it is at least 65% efficient, not 30.
Where is that math derived from??
Is the derivative of spark length power?
I'm just curious
Re: QCW coil
teravolt, Tue Dec 06 2011, 08:36PM
Hi Dr. Kilovolt I looked up KVAR and found that the formula goes as KVAR=(Kv)squared/1000XC.
maby those other caps are differant but who Knows what the maximum KVAR rating of a cap is unless it is given by the manufacturer. It is also probly based on the disapation factor of any cap or material. I'm shure that mica has a higer disapation factor than the doorknob material but that doesnt mean that you can't use them in sirton applications ass long as they dont excied ther KVAR rating
teravolt, Tue Dec 06 2011, 08:36PM
Hi Dr. Kilovolt I looked up KVAR and found that the formula goes as KVAR=(Kv)squared/1000XC.
maby those other caps are differant but who Knows what the maximum KVAR rating of a cap is unless it is given by the manufacturer. It is also probly based on the disapation factor of any cap or material. I'm shure that mica has a higer disapation factor than the doorknob material but that doesnt mean that you can't use them in sirton applications ass long as they dont excied ther KVAR rating
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