large tesla tuning question
teravolt, Fri Mar 30 2007, 04:52AMI am designing a fiber optic drive DRSSTC from scratch and I have enterd the stage for the primary construction. When I am ready what is the recomendation for tuning poles? I have the book "Building the modern day tesla coil" and Eastern Voltage Research said that in small ciols the primary is tuned low and does not go into larger coils. How do you guys deal with notching and large coils. If you need details of my DRSSTC let me know
Re: large tesla tuning question
Steve Ward, Fri Mar 30 2007, 03:58PM
Im sure ive explained this before, but with larger coils, i find that allowing a notch is fine (typically occurs in 6-9 cycles). The notch is then your shut off point, which maximizes efficiency overall. Its found that with big coils, you can typically drive enough energy in those 6-9 cycles to achieve good spark lengths, while little coils just cant get enough energy in that short time, so you detune very far to alter the effects of notching (it does ultimately notch, since this is a physical phenomena dealing with energy being transfered to the load).
But, you shouldnt have much to worry about designing. Make your primary have more inductance than you think you need, and then just find what tuning works best for your system since you will need to fine tune it by hand anyway.
And what exactly is meant by fiber optic drive? Just the interrupter or is the RF drive signal also by fiber?
Steve Ward, Fri Mar 30 2007, 03:58PM
Im sure ive explained this before, but with larger coils, i find that allowing a notch is fine (typically occurs in 6-9 cycles). The notch is then your shut off point, which maximizes efficiency overall. Its found that with big coils, you can typically drive enough energy in those 6-9 cycles to achieve good spark lengths, while little coils just cant get enough energy in that short time, so you detune very far to alter the effects of notching (it does ultimately notch, since this is a physical phenomena dealing with energy being transfered to the load).
But, you shouldnt have much to worry about designing. Make your primary have more inductance than you think you need, and then just find what tuning works best for your system since you will need to fine tune it by hand anyway.
And what exactly is meant by fiber optic drive? Just the interrupter or is the RF drive signal also by fiber?
Re: large tesla tuning question
teravolt, Sat Mar 31 2007, 05:20AM
thanks for the reply, I am using fiber optics to isolate 4 CM600HA-24. Each fiber runs the driver to each IGBT. I can get rise and fall times under a microsecond. Each driver uses an independent power supply (on board regulators). The same thing can be done with optos. I prefer this method to transformers because I feal it gives me more controle over the gate time. with 2 IXDD414PI I can drive the gate with less than an ohm at 28A or more.
teravolt, Sat Mar 31 2007, 05:20AM
thanks for the reply, I am using fiber optics to isolate 4 CM600HA-24. Each fiber runs the driver to each IGBT. I can get rise and fall times under a microsecond. Each driver uses an independent power supply (on board regulators). The same thing can be done with optos. I prefer this method to transformers because I feal it gives me more controle over the gate time. with 2 IXDD414PI I can drive the gate with less than an ohm at 28A or more.
Re: large tesla tuning question
ragnar, Sat Mar 31 2007, 05:44AM
Darnit, where do you and Firkragg find this beautiful double-sided tinned donut-pad-prototype-board?
edit: So-called "Vector" is it? I purchase it as "prototyping clad", but can only find single-sided bare copper, which corrodes so quickly. ^_^
ragnar, Sat Mar 31 2007, 05:44AM
Darnit, where do you and Firkragg find this beautiful double-sided tinned donut-pad-prototype-board?
edit: So-called "Vector" is it? I purchase it as "prototyping clad", but can only find single-sided bare copper, which corrodes so quickly. ^_^
Re: large tesla tuning question
Hazmatt_(The Underdog), Sat Mar 31 2007, 06:19AM
BP don't you know about Vector? It's out there but the stuff new is $$$
Hazmatt_(The Underdog), Sat Mar 31 2007, 06:19AM
BP don't you know about Vector? It's out there but the stuff new is $$$
Re: large tesla tuning question
Marko, Sat Mar 31 2007, 11:19AM
Hi! *jelaous of those beautiful bricks and drivers*
All my tinned boards are tinned on my own, they were copper before.
Anyway, due to lead contet solder oxidizes after some time and still hardens the soldering... I never tried a RoHS solder yet.
Using lotlack spray would actually make soldering more easy than tinning.
I did although have some silvered and gold-plated double sided proto boards here. They are superior for soldering under any conditions! I don't have much of them left unfortunately.
I also noticed that my coil notches after just few cycles whan I tuned it for *best looking spark*. I would have to run 2 notches if I wanted 200 or so us of on time.
I still need proper capacitors, calibrated CTs snd some time...
Marko, Sat Mar 31 2007, 11:19AM
Hi! *jelaous of those beautiful bricks and drivers*
Darnit, where do you and Firkragg find this beautiful double-sided tinned donut-pad-prototype-board?
All my tinned boards are tinned on my own, they were copper before.
Anyway, due to lead contet solder oxidizes after some time and still hardens the soldering... I never tried a RoHS solder yet.
Using lotlack spray would actually make soldering more easy than tinning.
I did although have some silvered and gold-plated double sided proto boards here. They are superior for soldering under any conditions! I don't have much of them left unfortunately.
Im sure ive explained this before, but with larger coils, i find that allowing a notch is fine (typically occurs in 6-9 cycles). The notch is then your shut off point, which maximizes efficiency overall. Its found that with big coils, you can typically drive enough energy in those 6-9 cycles to achieve good spark lengths, while little coils just cant get enough energy in that short time, so you detune very far to alter the effects of notching (it does ultimately notch, since this is a physical phenomena dealing with energy being transfered to the load).
I also noticed that my coil notches after just few cycles whan I tuned it for *best looking spark*. I would have to run 2 notches if I wanted 200 or so us of on time.
I still need proper capacitors, calibrated CTs snd some time...
Re: large tesla tuning question
Tom540, Sat Mar 31 2007, 04:52PM
Frys sells boards like that. If there isn't one near you you can try the website
I don't know if they ship overseas though.
Tom540, Sat Mar 31 2007, 04:52PM
Frys sells boards like that. If there isn't one near you you can try the website
I don't know if they ship overseas though.Re: large tesla tuning question
teravolt, Sat Mar 31 2007, 05:26PM
vector is to expensive so I use use Twin Industries [http://twinind.com/catalog.php?id=7] to do my prototype PCB's
. The driver PCB is done with ExpressPCB and there free softwere package. At some point I am going to make a surface mount version of the controler. I Got 100 of the 942C caps at Richardson Electronics in two weeks
teravolt, Sat Mar 31 2007, 05:26PM
vector is to expensive so I use use Twin Industries [http://twinind.com/catalog.php?id=7] to do my prototype PCB's
. The driver PCB is done with ExpressPCB and there free softwere package. At some point I am going to make a surface mount version of the controler. I Got 100 of the 942C caps at Richardson Electronics in two weeks
Re: large tesla tuning question
Marko, Sat Mar 31 2007, 07:13PM
Wow teravolt, absolutely beautiful design... There is a real demand for 942C caps in last times, guys at rell must be wondering about that...
Just spotted it, what are those busbars made off?
Marko, Sat Mar 31 2007, 07:13PM
Wow teravolt, absolutely beautiful design... There is a real demand for 942C caps in last times, guys at rell must be wondering about that...
Just spotted it, what are those busbars made off?
Re: large tesla tuning question
teravolt, Sat Mar 31 2007, 10:01PM
1/8"aluminuim plate 5.39uf esr less than 1m ohm
teravolt, Sat Mar 31 2007, 10:01PM
1/8"aluminuim plate 5.39uf esr less than 1m ohm
Re: large tesla tuning question
Steve Ward, Sat Mar 31 2007, 10:12PM
Very nice work there with the aluminum cabinet!
You might want to try moving the DC filter caps closer to the IGBTs to lower the bus inductance, but you can see if it will work as-is first, since it may very well be just fine.
Im assuming this will just be a half-bridge?
Oh, and very nice MMC bank
Steve Ward, Sat Mar 31 2007, 10:12PM
Very nice work there with the aluminum cabinet!
You might want to try moving the DC filter caps closer to the IGBTs to lower the bus inductance, but you can see if it will work as-is first, since it may very well be just fine.
Im assuming this will just be a half-bridge?
Oh, and very nice MMC bank
Re: large tesla tuning question
teravolt, Sun Apr 01 2007, 04:27AM
the configuration is a full bridge. Most people use poly caps at the IGBT, how do I detirmin what each amount of capasitance is?
teravolt, Sun Apr 01 2007, 04:27AM
the configuration is a full bridge. Most people use poly caps at the IGBT, how do I detirmin what each amount of capasitance is?
Re: large tesla tuning question
Steve Ward, Sun Apr 01 2007, 07:40AM
Typically you would just try some capacitance and see, but generally, you should *not* rely on poly caps right at the IGBTs to take care of transients. Instead, you should try to get the main electrolytic capacitors as close as possible to the IGBTs, which will keep transients down to begin with, then try some poly caps to see if it makes the transients better or *worse*. Many times, just sticking some caps on there can make the voltage spikes WORSE since these caps can resonate with the leakage inductance of your bus structure, causing the voltage across the IGBTs to climb very high (ive seen well over 2X the DC input voltage).
Steve Ward, Sun Apr 01 2007, 07:40AM
the configuration is a full bridge. Most people use poly caps at the IGBT, how do I detirmin what each amount of capasitance is?
Typically you would just try some capacitance and see, but generally, you should *not* rely on poly caps right at the IGBTs to take care of transients. Instead, you should try to get the main electrolytic capacitors as close as possible to the IGBTs, which will keep transients down to begin with, then try some poly caps to see if it makes the transients better or *worse*. Many times, just sticking some caps on there can make the voltage spikes WORSE since these caps can resonate with the leakage inductance of your bus structure, causing the voltage across the IGBTs to climb very high (ive seen well over 2X the DC input voltage).
Re: large tesla tuning question
teravolt, Mon Apr 02 2007, 03:14AM
thanks I am reworking my cap setup so there is no more than 5 to 6" from the caps to the IGBT with 4awg wire
teravolt, Mon Apr 02 2007, 03:14AM
thanks I am reworking my cap setup so there is no more than 5 to 6" from the caps to the IGBT with 4awg wire
Re: large tesla tuning question
teravolt, Mon Apr 02 2007, 03:46AM
I have 23000uf each for + and -. If there is more energy storage what can I expect other than heating. I would like to extend the the pulse time into the millisecond range. maby higher primary currents
teravolt, Mon Apr 02 2007, 03:46AM
I have 23000uf each for + and -. If there is more energy storage what can I expect other than heating. I would like to extend the the pulse time into the millisecond range. maby higher primary currents
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