Spiral impulse generator = rolled cap Blumlein induction coil!
Tesladownunder, Sat Apr 19 2008, 10:09AMThis is an odd little high voltage generator which is in principle, part Blumlein generator (like the nitrogen laser uses) and part induction coil. It is very simple and compact and very easy to make. They have two copper strips insulated from each other and rolled up like a rolled capacitor. Apply a few kV at one end of both strips and they will charge up. Short circuit one end with a spark gap and a very fast pulse passes in the Blumlein capacitor strips. This will have a magnetic effect as the current in each copper strip (my brain starts to hurt here) will have an additive effect and like current in a coil will result in magnetic induction in the remaining turns of copper strip.
The first photo shows the spiral impulse generator generating a 5 mm spark (perhaps 5 kV) from a 1 mm spark gap. The spark gap is between the two electrodes (which are not connected to each other) and the right upper electrode is the one that continues through to the output electrode strip with the longer spark coming off it. The capacitance between the two strips is 900 pF.
The second photo shows the 1984 patent that this comes from.
The next photo shows the strips of copper foil of 10 x 62 mm. I have soldered two together for the long winding. Hence there are two parallel strips of 4.5 turns and one strip only continues on for another 4.5 turns.
The last photo shows the start of the copper strip windings separated by polyethylene sheet.
It doesn't seem too efficient but I don't really understand the setup enough to know which way to modify it best. I imagine that I could make one with more turns to start.
TDU
Re: Spiral impulse generator = rolled cap Blumlein induction coil!
Proud Mary, Sat Apr 19 2008, 01:17PM
How intriguing!
I have found another patent, which discusses the problems of increasing the power output of the basic spiral, in order to put forward a method of its own for reaching into the megavolt range from a 10kV supply:
Multi winding spiral generator United States Patent 5567995
Proud Mary, Sat Apr 19 2008, 01:17PM
How intriguing!
I have found another patent, which discusses the problems of increasing the power output of the basic spiral, in order to put forward a method of its own for reaching into the megavolt range from a 10kV supply:
Multi winding spiral generator United States Patent 5567995
Re: Spiral impulse generator = rolled cap Blumlein induction coil!
uzzors2k, Sat Apr 19 2008, 05:43PM
It seems like these can have large multiplication ratios. The one here has a step up ratio of 16 at 9kV! A simple alternative to Marx generators maybe, if we can figure out how to make them that efficient.
uzzors2k, Sat Apr 19 2008, 05:43PM
It seems like these can have large multiplication ratios. The one here has a step up ratio of 16 at 9kV! A simple alternative to Marx generators maybe, if we can figure out how to make them that efficient.
Re: Spiral impulse generator = rolled cap Blumlein induction coil!
Spedy, Sat Apr 19 2008, 07:09PM
Wait a sec, I'm confused here.
so, you short circuit it and it makes a bigger spark where you short circuit it? I don;t get it...
Oh wait, Is it like this?
Spedy, Sat Apr 19 2008, 07:09PM
Wait a sec, I'm confused here.
so, you short circuit it and it makes a bigger spark where you short circuit it? I don;t get it...
Oh wait, Is it like this?
Re: Spiral impulse generator = rolled cap Blumlein induction coil!
Proud Mary, Sat Apr 19 2008, 09:05PM
I have found an explanation of the operation of the spiral line here:
Proud Mary, Sat Apr 19 2008, 09:05PM
I have found an explanation of the operation of the spiral line here:
Re: Spiral impulse generator = rolled cap Blumlein induction coil!
Dr. Shark, Sat Apr 19 2008, 09:56PM
Wow, what an amazing concept. I went right ahead and tried to make one
but I could not get it to work yet. Maybe it is a little small, is is constructed from a single rolled up overhead sheet so the "secondary" (is it still called that in electrodynamics?) is only 70cm long or so, which is about a third of what Peter has.
I'll keep playing with it though, especially the thread linked to by Uzzors makes it seem really worthwhile. I'll have to be able to puncture that OHP sheet!
EDIT: Well, I sort of got it to work by cutting down on the extra insulation material (pun intended). Still the output spark is rather puny, about the same as a piezo lighter.
I don't think there is anything magical or electrodynamical about this circuit as I build it, at least I can explain without the electric field vectors, traveling waves, reflections and all that. After all it IS just a Tesla coil with tank capacitor and the primary scrambled up. So it does not take the slightest bit of waves propagating at the speed of light to get a spark at the output.
I am pretty sure the "real" Blümlein pulseforming lines, which are used for creating nanosecond pulses, take a lot more work that just rolling up a piece of tinfoil. Have a look here for some Blümlein bashing, although that may just be a minority opinion.
Dr. Shark, Sat Apr 19 2008, 09:56PM
Wow, what an amazing concept. I went right ahead and tried to make one
but I could not get it to work yet. Maybe it is a little small, is is constructed from a single rolled up overhead sheet so the "secondary" (is it still called that in electrodynamics?) is only 70cm long or so, which is about a third of what Peter has.
I'll keep playing with it though, especially the thread linked to by Uzzors makes it seem really worthwhile. I'll have to be able to puncture that OHP sheet!
EDIT: Well, I sort of got it to work by cutting down on the extra insulation material (pun intended). Still the output spark is rather puny, about the same as a piezo lighter.
I don't think there is anything magical or electrodynamical about this circuit as I build it, at least I can explain without the electric field vectors, traveling waves, reflections and all that. After all it IS just a Tesla coil with tank capacitor and the primary scrambled up. So it does not take the slightest bit of waves propagating at the speed of light to get a spark at the output.
I am pretty sure the "real" Blümlein pulseforming lines, which are used for creating nanosecond pulses, take a lot more work that just rolling up a piece of tinfoil. Have a look here
for some Blümlein bashing, although that may just be a minority opinion.Re: Spiral impulse generator = rolled cap Blumlein induction coil!
Proud Mary, Sat Apr 19 2008, 11:45PM
N2 lasers need nanosecond pumping, which makes a practical Blumlein difficult to implement, but more usual Blumlein configurations in the microsecond pulse range are not at all difficult to construct, and drive with a rotary spark gap, as this paper shows:
You just need to have the money to buy RG213 coaxial cable!
Proud Mary, Sat Apr 19 2008, 11:45PM
Dr. Shark wrote ...
I am pretty sure the "real" Blümlein pulseforming lines, which are used for creating nanosecond pulses, take a lot more work that just rolling up a piece of tinfoil. Have a look here for some Blümlein bashing, although that may just be a minority opinion.
I am pretty sure the "real" Blümlein pulseforming lines, which are used for creating nanosecond pulses, take a lot more work that just rolling up a piece of tinfoil. Have a look here
for some Blümlein bashing, although that may just be a minority opinion.N2 lasers need nanosecond pumping, which makes a practical Blumlein difficult to implement, but more usual Blumlein configurations in the microsecond pulse range are not at all difficult to construct, and drive with a rotary spark gap, as this paper shows:
You just need to have the money to buy RG213 coaxial cable!
Re: Spiral impulse generator = rolled cap Blumlein induction coil!
jpsmith123, Sat Apr 19 2008, 11:45PM
Somewhere I have a few pdf papers on these things. If anyone is interested maybe I can try to find them and upload them somewhere.
The one paper I don't have is the one referenced in the following linked paper, which apparently discusses the detailed design.
(Wrt blumlein pulse generators it seems that the limiting factor for short, fast pulses is the switch...for fast di/dt you need high electric field across the spark gap which generally means pressurized gas or a liquid dielectric. BTW here's an interesting paper on a fast blumlein pulser
jpsmith123, Sat Apr 19 2008, 11:45PM
Somewhere I have a few pdf papers on these things. If anyone is interested maybe I can try to find them and upload them somewhere.
The one paper I don't have is the one referenced in the following linked paper, which apparently discusses the detailed design.
(Wrt blumlein pulse generators it seems that the limiting factor for short, fast pulses is the switch...for fast di/dt you need high electric field across the spark gap which generally means pressurized gas or a liquid dielectric. BTW here's an interesting paper on a fast blumlein pulser
Re: Spiral impulse generator = rolled cap Blumlein induction coil!
Tesladownunder, Sun Apr 20 2008, 02:57AM
Here are a couple of diagrams to clarify the setup.
There is no connection between the two HV electrodes. It does not resemble a TC at all (although something similar might be feasible but that is another project).
There is a standard two parallel electrode strips rolled up like a home made rolled cap. The extended one just allows more voltage step up.
Actually, I don't know how much induction there really is and how much is just transmission line coupling.
BTW for all those who wondered why their rolled caps failed at the ends, this is why. A few weeks ago, I autopsied 2 of my old big rolled caps to dispose of the oil and the failure was at the ends away from the electrode attachment, ie where the HV is picked up.
Tesladownunder, Sun Apr 20 2008, 02:57AM
Here are a couple of diagrams to clarify the setup.
There is no connection between the two HV electrodes. It does not resemble a TC at all (although something similar might be feasible but that is another project).
There is a standard two parallel electrode strips rolled up like a home made rolled cap. The extended one just allows more voltage step up.
Actually, I don't know how much induction there really is and how much is just transmission line coupling.
BTW for all those who wondered why their rolled caps failed at the ends, this is why. A few weeks ago, I autopsied 2 of my old big rolled caps to dispose of the oil and the failure was at the ends away from the electrode attachment, ie where the HV is picked up.
Re: Spiral impulse generator = rolled cap Blumlein induction coil!
Mates, Sun Apr 20 2008, 07:27AM
I have few ideas regarding this thread...
What about to try coax cable istead of the rolled-insutated stripes...Would it work?
And it would be interesting to try solidstate based "spark gap" because as understand this concept it has no real frequency limit (maybe such device could be used for plasma speakers ???)
Mates, Sun Apr 20 2008, 07:27AM
I have few ideas regarding this thread...
What about to try coax cable istead of the rolled-insutated stripes...Would it work?
And it would be interesting to try solidstate based "spark gap" because as understand this concept it has no real frequency limit (maybe such device could be used for plasma speakers ???)
Re: Spiral impulse generator = rolled cap Blumlein induction coil!
Tesladownunder, Sun Apr 20 2008, 07:52AM
If you have 50m of coax and are happy to setup some spark gaps then you can make a tripler but this is capable of greater multiplication of voltage and is much more compact.
Somehow, I dont see solid state being that good at 100 nanosecond switching at 10kV. Spark gaps are free, Klystrons are available but acres of high voltage fast silicon is not how I would go. Not today at least...
I am making a larger one for experiments with about 10 times the capacitance (10nF). Might not get it done tonight though.
TDU
Tesladownunder, Sun Apr 20 2008, 07:52AM
If you have 50m of coax and are happy to setup some spark gaps then you can make a tripler but this is capable of greater multiplication of voltage and is much more compact.
Somehow, I dont see solid state being that good at 100 nanosecond switching at 10kV. Spark gaps are free, Klystrons are available but acres of high voltage fast silicon is not how I would go. Not today at least...
I am making a larger one for experiments with about 10 times the capacitance (10nF). Might not get it done tonight though.
TDU
Re: Spiral impulse generator = rolled cap Blumlein induction coil!
flannelhead, Sun Apr 20 2008, 09:05AM
Does it have to be copper or could I try with aluminium foil?
flannelhead, Sun Apr 20 2008, 09:05AM
Does it have to be copper or could I try with aluminium foil?
Re: Spiral impulse generator = rolled cap Blumlein induction coil!
Proud Mary, Sun Apr 20 2008, 09:40AM
Aluminium will work fine.
Proud Mary, Sun Apr 20 2008, 09:40AM
spark wrote ...
Does it have to be copper or could I try with aluminium foil?
Does it have to be copper or could I try with aluminium foil?
Aluminium will work fine.
Re: Spiral impulse generator = rolled cap Blumlein induction coil!
Bored Chemist, Sun Apr 20 2008, 09:41AM
I have dismantled a commercial one of these from a portable xray unit (dead, alas). It had a ferrite core.
You might want to add a core of some sort and see what happens.
Bored Chemist, Sun Apr 20 2008, 09:41AM
I have dismantled a commercial one of these from a portable xray unit (dead, alas). It had a ferrite core.
You might want to add a core of some sort and see what happens.
Re: Spiral impulse generator = rolled cap Blumlein induction coil!
jpsmith123, Sun Apr 20 2008, 12:04PM
Strictly speaking, I think you can't make a "spiral" generator from coax...but you can make a "stacked blumlein".
jpsmith123, Sun Apr 20 2008, 12:04PM
Mates wrote ...
I have few ideas regarding this thread...
What about to try coax cable istead of the rolled-insutated stripes...Would it work?
And it would be interesting to try solidstate based "spark gap" because as understand this concept it has no real frequency limit (maybe such device could be used for plasma speakers ???)
I have few ideas regarding this thread...
What about to try coax cable istead of the rolled-insutated stripes...Would it work?
And it would be interesting to try solidstate based "spark gap" because as understand this concept it has no real frequency limit (maybe such device could be used for plasma speakers ???)
Strictly speaking, I think you can't make a "spiral" generator from coax...but you can make a "stacked blumlein".
Re: Spiral impulse generator = rolled cap Blumlein induction coil!
Proud Mary, Sun Apr 20 2008, 02:44PM
This design using flat ribbon cable has to be the easiest and simplest spiral generator I've found yet:
"Stripline transformer adapted for inexpensive construction"
United States Patent 4717834
Proud Mary, Sun Apr 20 2008, 02:44PM
This design using flat ribbon cable has to be the easiest and simplest spiral generator I've found yet:
"Stripline transformer adapted for inexpensive construction"
United States Patent 4717834
Re: Spiral impulse generator = rolled cap Blumlein induction coil!
Mates, Sun Apr 20 2008, 08:53PM
How important is to make one of the stripes longer? Does it affect the pulse duration and/or the final voltage?
Mates, Sun Apr 20 2008, 08:53PM
How important is to make one of the stripes longer? Does it affect the pulse duration and/or the final voltage?
Re: Spiral impulse generator = rolled cap Blumlein induction coil!
Tesladownunder, Sun Apr 20 2008, 11:56PM
I wonder if the ribbon is not just convenient but is also acting like Litz wire and hence possibly more efficient.
It should handle more voltage too, since the voltage is evenly spaced between turns.
I have about 20m or more of 3m wide poly of the same sort I used for the small one. Alfoil is cheap so a really big generator run at higher voltages might be feasible. The problem with alfoil is the termination at the spark gap end which needs to be low inductance and low resistance. I've not found aluminum solders to be that effective. Fortunately I have a few square meters of copper foil which solders nicely.
TDU
Tesladownunder, Sun Apr 20 2008, 11:56PM
Harry wrote ...
This design using flat ribbon cable has to be the easiest and simplest spiral generator I've found yet:
"Stripline transformer adapted for inexpensive construction"
Sounds pretty easy. 12 feet of 8 core ribbon and a aluminium foil strip around a 1.9 inch former with a mercury wetted relay switching 160 V to get 2500 V peak at 20ns.This design using flat ribbon cable has to be the easiest and simplest spiral generator I've found yet:
"Stripline transformer adapted for inexpensive construction"
I wonder if the ribbon is not just convenient but is also acting like Litz wire and hence possibly more efficient.
It should handle more voltage too, since the voltage is evenly spaced between turns.
I have about 20m or more of 3m wide poly of the same sort I used for the small one. Alfoil is cheap so a really big generator run at higher voltages might be feasible. The problem with alfoil is the termination at the spark gap end which needs to be low inductance and low resistance. I've not found aluminum solders to be that effective. Fortunately I have a few square meters of copper foil which solders nicely.
TDU
Re: Spiral impulse generator = rolled cap Blumlein induction coil!
Proud Mary, Mon Apr 21 2008, 12:37AM
From what I've understood so far, the maximum output voltage is given by Vout = 2nVin, where n is the number of turns.
The total charge is that which can be stored on the two strips in straightforward capacitor mode, so the more surface area the strips have, the greater the output pulse power. I'm not clear if the flat ribbon shorted across both ends can act as though it were a single capacitive electrode in relation to the ground plane or not.
I agree about the problem of making reliable low Z connections to aluminium foil, which I would prefer to use rather than my small stock of self-adhesive copper foil and sheet.
As a first attempt, I thought of making a sandwich of 75mm aluminium adhesive tape and 100mm insulating tape with one sticky side down, but don't want to commit money to it till I have a better understanding of how thick the insulation needs to be, because there'll be no unpicking it all if the dielectric breaks down.
As I understand it, the insulation needs to increase in proportion with the number of turns, which can result in high voltage Vector Inversion Generators becoming physically large.
Proud Mary, Mon Apr 21 2008, 12:37AM
From what I've understood so far, the maximum output voltage is given by Vout = 2nVin, where n is the number of turns.
The total charge is that which can be stored on the two strips in straightforward capacitor mode, so the more surface area the strips have, the greater the output pulse power. I'm not clear if the flat ribbon shorted across both ends can act as though it were a single capacitive electrode in relation to the ground plane or not.
I agree about the problem of making reliable low Z connections to aluminium foil, which I would prefer to use rather than my small stock of self-adhesive copper foil and sheet.
As a first attempt, I thought of making a sandwich of 75mm aluminium adhesive tape and 100mm insulating tape with one sticky side down, but don't want to commit money to it till I have a better understanding of how thick the insulation needs to be, because there'll be no unpicking it all if the dielectric breaks down.
As I understand it, the insulation needs to increase in proportion with the number of turns, which can result in high voltage Vector Inversion Generators becoming physically large.
Re: Spiral impulse generator = rolled cap Blumlein induction coil!
Proud Mary, Mon Apr 21 2008, 11:26AM
I see that NASA has a page on Vector Inversion Generators in its commercial successes section:
Proud Mary, Mon Apr 21 2008, 11:26AM
I see that NASA has a page on Vector Inversion Generators in its commercial successes section:
Re: Spiral impulse generator = rolled cap Blumlein induction coil!
Mates, Mon Apr 21 2008, 03:38PM
As I understand the concept, than the demands on the dielectric strength of insulation layer should be constant within the whole coil (why it should increase???). But for higher voltages the oil bath seems to be necessary to prevent the side sparking...
Definitely very interesting concept… I'm already getting a roll of suitable plastic sheet.
BTW: Soldering of aluminum should be possible with special solder material. I've never tried by myself but my friend told me it is piece of cake in case you have the proper solder.
Mates, Mon Apr 21 2008, 03:38PM
Harry wrote ...
As I understand it, the insulation needs to increase in proportion with the number of turns, which can result in high voltage Vector Inversion Generators becoming physically large.
As I understand it, the insulation needs to increase in proportion with the number of turns, which can result in high voltage Vector Inversion Generators becoming physically large.
As I understand the concept, than the demands on the dielectric strength of insulation layer should be constant within the whole coil (why it should increase???). But for higher voltages the oil bath seems to be necessary to prevent the side sparking...
Definitely very interesting concept… I'm already getting a roll of suitable plastic sheet.
BTW: Soldering of aluminum should be possible with special solder material. I've never tried by myself but my friend told me it is piece of cake in case you have the proper solder.
Re: Spiral impulse generator = rolled cap Blumlein induction coil!
Proud Mary, Mon Apr 21 2008, 05:32PM
Doesn't the pulse grow in amplitude as it travels round each succeeding turn of the spiral line? Surely the maximum voltage of the pulse only appears for a moment at the output end of the active line, or have I got something wrong here?
Proud Mary, Mon Apr 21 2008, 05:32PM
Mates wrote ...
As I understand the concept, than the demands on the dielectric strength of insulation layer should be constant within the whole coil (why it should increase???).
As I understand the concept, than the demands on the dielectric strength of insulation layer should be constant within the whole coil (why it should increase???).
Doesn't the pulse grow in amplitude as it travels round each succeeding turn of the spiral line? Surely the maximum voltage of the pulse only appears for a moment at the output end of the active line, or have I got something wrong here?
Re: Spiral impulse generator = rolled cap Blumlein induction coil!
Mates, Mon Apr 21 2008, 06:02PM
Yes, that's the point - the maximum voltage difference will be between the end and the beginning of the stripe. So these two ends are separated by so many layers of insulation how many turns you have... But maybe I'm wrong because it's hard to say what will be the potential difference between the active and passive stripe which are insulated only by one layer all the time ...
Mates, Mon Apr 21 2008, 06:02PM
Harry wrote ...
Surely the maximum voltage of the pulse only appears for a moment at the output end of the active line...
Surely the maximum voltage of the pulse only appears for a moment at the output end of the active line...
Yes, that's the point - the maximum voltage difference will be between the end and the beginning of the stripe. So these two ends are separated by so many layers of insulation how many turns you have... But maybe I'm wrong because it's hard to say what will be the potential difference between the active and passive stripe which are insulated only by one layer all the time ...
Re: Spiral impulse generator = rolled cap Blumlein induction coil!
Proud Mary, Mon Apr 21 2008, 06:26PM
I now think perhaps you were right to start with - that the voltage across the end of the active and passive lines will still only be 2V because the relative charge on the passive line will go up as well with each succeeding turn.
Like you, I see this as being a device that would be most reliable under oil. If glass fibre tapes (as used in boat building) were used for the interwinding insulation, then they would saturate with oil and be self-repairing.
Proud Mary, Mon Apr 21 2008, 06:26PM
Mates wrote ...
But maybe I'm wrong because it's hard to say what will be the potential difference between the active and passive stripe which are insulated only by one layer all the time ...
But maybe I'm wrong because it's hard to say what will be the potential difference between the active and passive stripe which are insulated only by one layer all the time ...
I now think perhaps you were right to start with - that the voltage across the end of the active and passive lines will still only be 2V because the relative charge on the passive line will go up as well with each succeeding turn.
Like you, I see this as being a device that would be most reliable under oil. If glass fibre tapes (as used in boat building) were used for the interwinding insulation, then they would saturate with oil and be self-repairing.
Re: Spiral impulse generator = rolled cap Blumlein induction coil!
Dr. Shark, Mon Apr 21 2008, 09:44PM
I made another one of these, maybe if I post a few picture of the construction it will help others. I used overhead sheets and kitchen foil, so the construction is slightly less "professional" than Peter's. I started by cutting up Mylar® overhead slides into 16 stripes of 5 cm width. Pasting them together gave me a short strip about 50cm long and a long strip of about 4m, which equates to roughly 5 turns and 40 turns. Next I invented a funny way of obtaining a 3cm wide strip of aluminium foil from kitchen foil. These were rolled up per Peters instructions, adding short pieces of copper foil (from a ATX PSU transformer) to give the terminals. The last pic shows the end result with a ferrite core that I intend to use with it.
Now I'll go see whether it works!
Dr. Shark, Mon Apr 21 2008, 09:44PM
I made another one of these, maybe if I post a few picture of the construction it will help others. I used overhead sheets and kitchen foil, so the construction is slightly less "professional" than Peter's. I started by cutting up Mylar® overhead slides into 16 stripes of 5 cm width. Pasting them together gave me a short strip about 50cm long and a long strip of about 4m, which equates to roughly 5 turns and 40 turns. Next I invented a funny way of obtaining a 3cm wide strip of aluminium foil from kitchen foil. These were rolled up per Peters instructions, adding short pieces of copper foil (from a ATX PSU transformer) to give the terminals. The last pic shows the end result with a ferrite core that I intend to use with it.
Now I'll go see whether it works!
Re: Spiral impulse generator = rolled cap Blumlein induction coil!
Tesladownunder, Mon Apr 21 2008, 11:23PM
Well, the ferrite improves the performance as far as sparks are concerned. They are more intense and now are out to about 8mm.
It is now possible to use the full voltage input (3kV DC peak = peak of 4kV NST half wave rectified). The air core version performance was best with a small intense spark and got smaller with a bigger voltage input. The ferrite one improves with increasing voltage.
I guess this confirms that there is some induction acting in the setup. I imagine the pulse width has gone up considerably though.
TDU
Tesladownunder, Mon Apr 21 2008, 11:23PM
Well, the ferrite improves the performance as far as sparks are concerned. They are more intense and now are out to about 8mm.
It is now possible to use the full voltage input (3kV DC peak = peak of 4kV NST half wave rectified). The air core version performance was best with a small intense spark and got smaller with a bigger voltage input. The ferrite one improves with increasing voltage.
I guess this confirms that there is some induction acting in the setup. I imagine the pulse width has gone up considerably though.
TDU
Re: Spiral impulse generator = rolled cap Blumlein induction coil!
Weston, Tue Apr 22 2008, 02:23AM
Like mentioned I used a Coxal cable. I have seemed to have made a mini Tesla coil. I can light up florescent tubes and neon bulbs with out direct electrical contact. I provided the voltage with a flash camera operated voltage multiplier.
Weston, Tue Apr 22 2008, 02:23AM
Like mentioned I used a Coxal cable. I have seemed to have made a mini Tesla coil. I can light up florescent tubes and neon bulbs with out direct electrical contact. I provided the voltage with a flash camera operated voltage multiplier.
Re: Spiral impulse generator = rolled cap Blumlein induction coil!
Dr. Shark, Tue Apr 22 2008, 08:28AM
I hate to be the one to criticize this neat idea, but I find the performance of Peter's and my VIG rather disappointing. In the thread here there is talk of 6 inch sparks, but looking at Peter's pictures his VIG seems to be as weak as mine. Even with the increased number of turns (I have 40) and the ferrite core, there is no discernible boost in performance.
Maybe a better understanding of the device would be in order, as from the papers I have been reading so far there are no hard design guidelines as to what works and what does not.
I don't think there is any "tuning" that can be done with the device, at least there is no resonant frequency to hit, so the best we can do is a clever trade-off of inductance and capacitance in the circuit. This allows tuning the output impedance, but should not affect voltage much.
The variable most deserving of further investigation is probably the turns ratio. Since the "original" Fitch generator had an 1:1 ratio, it may not be such a good idea after all to use a lot more secondary turns. The extra turns don't do any "vector inversion" but just provide transformer action, which may not work so well with the masive inter-turn capacitance. On a more pragmatic level, having more primary (rather than secondary) turns increases the capacitive energy storage, so you get more bang regardless of efficiency.
Dr. Shark, Tue Apr 22 2008, 08:28AM
I hate to be the one to criticize this neat idea, but I find the performance of Peter's and my VIG rather disappointing. In the thread here
there is talk of 6 inch sparks, but looking at Peter's pictures his VIG seems to be as weak as mine. Even with the increased number of turns (I have 40) and the ferrite core, there is no discernible boost in performance.Maybe a better understanding of the device would be in order, as from the papers I have been reading so far there are no hard design guidelines as to what works and what does not.
I don't think there is any "tuning" that can be done with the device, at least there is no resonant frequency to hit, so the best we can do is a clever trade-off of inductance and capacitance in the circuit. This allows tuning the output impedance, but should not affect voltage much.
The variable most deserving of further investigation is probably the turns ratio. Since the "original" Fitch generator had an 1:1 ratio, it may not be such a good idea after all to use a lot more secondary turns. The extra turns don't do any "vector inversion" but just provide transformer action, which may not work so well with the masive inter-turn capacitance. On a more pragmatic level, having more primary (rather than secondary) turns increases the capacitive energy storage, so you get more bang regardless of efficiency.
Re: Spiral impulse generator = rolled cap Blumlein induction coil!
Proud Mary, Tue Apr 22 2008, 08:46AM
So far as I can understand it from the various patents for spiral generators with ferrite cores, the ferrite acts by reducing the oscillatory frequency - slowing the decay - on the passive (slow) line, and thereby improving overall voltage and power efficiency.
I also found this interesting statement in the abstract of a paper:
In this paper, we will show that there is a functional relationship between the value of diameter to number of turns ratio (D/n) and the voltage efficiency. This is understandable in the context that for a given diameter, the diameter determines the characteristic "speed" of the "slow" part of the VIG while the length which is directly proportional to the number of turns determines the characteristic "speed" of the fast side. Thus, the D/n ratio is a measure of the ratio of the high/low frequency components of the generator
Characterization and applications of vector inversion generators
Merryman, S.A.; Rose, M.F.; Shotts, Z.
Pulsed Power Conference, 2003. Digest of Technical Papers. PPC-2003. 14th IEEE International
Volume 1, Issue , 15-18 June 2003 Page(s): 249 - 252 Vol.1
Unfortunately, I don't have access to the full text, but the statement suggests the reason why some designs add some extra windings to the active fast line and not the passive slow line.
On a practical note, another patent packs the VIG cores with ferrite rods, which is good for me, as I have a box of 'em.
PORTABLE X-RAY GENERATING MACHINE
United States Patent US3681604
Proud Mary, Tue Apr 22 2008, 08:46AM
Tesladownunder wrote ...
I guess this confirms that there is some induction acting in the setup. I imagine the pulse width has gone up considerably though.
TDU
I guess this confirms that there is some induction acting in the setup. I imagine the pulse width has gone up considerably though.
TDU
So far as I can understand it from the various patents for spiral generators with ferrite cores, the ferrite acts by reducing the oscillatory frequency - slowing the decay - on the passive (slow) line, and thereby improving overall voltage and power efficiency.
I also found this interesting statement in the abstract of a paper:
In this paper, we will show that there is a functional relationship between the value of diameter to number of turns ratio (D/n) and the voltage efficiency. This is understandable in the context that for a given diameter, the diameter determines the characteristic "speed" of the "slow" part of the VIG while the length which is directly proportional to the number of turns determines the characteristic "speed" of the fast side. Thus, the D/n ratio is a measure of the ratio of the high/low frequency components of the generator
Characterization and applications of vector inversion generators
Merryman, S.A.; Rose, M.F.; Shotts, Z.
Pulsed Power Conference, 2003. Digest of Technical Papers. PPC-2003. 14th IEEE International
Volume 1, Issue , 15-18 June 2003 Page(s): 249 - 252 Vol.1
Unfortunately, I don't have access to the full text, but the statement suggests the reason why some designs add some extra windings to the active fast line and not the passive slow line.
On a practical note, another patent packs the VIG cores with ferrite rods, which is good for me, as I have a box of 'em.
PORTABLE X-RAY GENERATING MACHINE
United States Patent US3681604
Re: Spiral impulse generator = rolled cap Blumlein induction coil!
Dr. Shark, Tue Apr 22 2008, 09:37AM
Dr. Shark, Tue Apr 22 2008, 09:37AM
Harry wrote ...
Unfortunately, I don't have access to the full text, but the statement suggests the reason why some designs add some extra windings to the active fast line and not the passive slow line.
You do now, check your PMs.Unfortunately, I don't have access to the full text, but the statement suggests the reason why some designs add some extra windings to the active fast line and not the passive slow line.
Re: Spiral impulse generator = rolled cap Blumlein induction coil!
Proud Mary, Tue Apr 22 2008, 10:12AM
Thank you so much Dr Shark! Its amazing that such a simple device wasn't discovered until the 1960s, and that professional scientists were still trying to explain how it works in this 2003 paper.
I like to have as much understanding as I can before I start on a project, because I've wasted so much time and money in the past on building things which didn't work properly because I didn't understand all the principles involved.
Proud Mary, Tue Apr 22 2008, 10:12AM
Dr. Shark wrote ...
Harry wrote ...
Unfortunately, I don't have access to the full text, but the statement suggests the reason why some designs add some extra windings to the active fast line and not the passive slow line.
You do now, check your PMs. Unfortunately, I don't have access to the full text, but the statement suggests the reason why some designs add some extra windings to the active fast line and not the passive slow line.
Thank you so much Dr Shark! Its amazing that such a simple device wasn't discovered until the 1960s, and that professional scientists were still trying to explain how it works in this 2003 paper.
I like to have as much understanding as I can before I start on a project, because I've wasted so much time and money in the past on building things which didn't work properly because I didn't understand all the principles involved.
Re: Spiral impulse generator = rolled cap Blumlein induction coil!
Dr. Shark, Tue Apr 22 2008, 10:26AM
Harry, I completely agree with you, especially after I essentially wasted most of last night constructing a bit of a dud. I already edited my above post to reflect my latest ideas, but I'll repeat:
The only reference that claims an improved output with extra secondary turns is the 1984 patent Peter cited in his first post. This looks more like an ordinary transformer to me than a VIG, although the two are of course intimately interrelated. As I understand the VIG, there is a cycle of LC oscillation which reverses the voltage on the capacitor, so the energy has to be stored in the magnetic field as the voltage crosses zero. At this point, a voltage would be induced in the additional turns. Thus the "extended VIG" seems to be quite different from a normal VIG in its operating principle.
All other references I could find about VIGs just use a 1:1 turns ratio, so that is what I will try tonight. Rewinding my VIG is pretty straightforward, so I'll see if that helps and report back.
Dr. Shark, Tue Apr 22 2008, 10:26AM
Harry, I completely agree with you, especially after I essentially wasted most of last night constructing a bit of a dud. I already edited my above post to reflect my latest ideas, but I'll repeat:
The only reference that claims an improved output with extra secondary turns is the 1984 patent Peter cited in his first post. This looks more like an ordinary transformer to me than a VIG, although the two are of course intimately interrelated. As I understand the VIG, there is a cycle of LC oscillation which reverses the voltage on the capacitor, so the energy has to be stored in the magnetic field as the voltage crosses zero. At this point, a voltage would be induced in the additional turns. Thus the "extended VIG" seems to be quite different from a normal VIG in its operating principle.
All other references I could find about VIGs just use a 1:1 turns ratio, so that is what I will try tonight. Rewinding my VIG is pretty straightforward, so I'll see if that helps and report back.
Re: Spiral impulse generator = rolled cap Blumlein induction coil!
Proud Mary, Tue Apr 22 2008, 10:55AM
Having got the paper thanks to our friend Dr Shark, and seen the information on the D/n ratio in Table 1, I feel able to begin a modest proof of concept model.
I've decided to use 75mm aluminium adhesive tape for the lines, and a double thickness of 100mm adhesive insulating tape as the dielectric, with a bundle of ferrite rods as the core.
I have the ferrite rods, but will have to send off to ebay for the aluminium tape and the extra-wide insulating tape, so won't be able to do anything in a hurry.
I've not made my mind up on the switch, but suppose I will go for a self-igniting spark gap to start with, which should be OK with a 3kV charge voltage from a Bertrand PSU I have to hand. I will charge a reservoir capacitor first, and power the VIG from that after disconnecting the supply, as I see from various patents that the EMP from VIGs can destroy electronic equipment nearby, or to which it is coupled, so it seems to me to need its own separate low Z earth.
Proud Mary, Tue Apr 22 2008, 10:55AM
Having got the paper thanks to our friend Dr Shark, and seen the information on the D/n ratio in Table 1, I feel able to begin a modest proof of concept model.
I've decided to use 75mm aluminium adhesive tape for the lines, and a double thickness of 100mm adhesive insulating tape as the dielectric, with a bundle of ferrite rods as the core.
I have the ferrite rods, but will have to send off to ebay for the aluminium tape and the extra-wide insulating tape, so won't be able to do anything in a hurry.
I've not made my mind up on the switch, but suppose I will go for a self-igniting spark gap to start with, which should be OK with a 3kV charge voltage from a Bertrand PSU I have to hand. I will charge a reservoir capacitor first, and power the VIG from that after disconnecting the supply, as I see from various patents that the EMP from VIGs can destroy electronic equipment nearby, or to which it is coupled, so it seems to me to need its own separate low Z earth.
Re: Spiral impulse generator = rolled cap Blumlein induction coil!
jpsmith123, Tue Apr 22 2008, 11:02AM
Could someone please send me that paper by Rose et al.? Thanks.
jpsmith123, Tue Apr 22 2008, 11:02AM
Could someone please send me that paper by Rose et al.? Thanks.
Re: Spiral impulse generator = rolled cap Blumlein induction coil!
Dago, Tue Apr 22 2008, 12:21PM
I'm interested in the discharge length, does anyone have equipment to measure such short pulses?
Dago, Tue Apr 22 2008, 12:21PM
I'm interested in the discharge length, does anyone have equipment to measure such short pulses?
Re: Spiral impulse generator = rolled cap Blumlein induction coil!
Dr. Shark, Tue Apr 22 2008, 01:05PM
I would not count on the pulses being that short, after all there is considerable inductance in the circuit from coiling up the transmission line. In the papers I looked at the discharge in in the order of a microsecond, which is not what I would call short.
Dr. Shark, Tue Apr 22 2008, 01:05PM
I would not count on the pulses being that short, after all there is considerable inductance in the circuit from coiling up the transmission line. In the papers I looked at the discharge in in the order of a microsecond, which is not what I would call short.
Re: Spiral impulse generator = rolled cap Blumlein induction coil!
Proud Mary, Tue Apr 22 2008, 01:32PM
"The pulsewidth is equal to 2nt Ï„t where nt is the number of turns and Ï„t is the average one way propagation time for a single turn. If t = 0 represents the closing of the switch, the leading edge of the output pulse is delayed by an amount nt Ï„t which for many applications is unimportant."
Source: Fast risetime spiral pulse generator
United States Patent 4140917
For practical purposes, I would reckon on the real life pulse being perhaps twice as long as the theory.
The pulses are triangular, but they could always be sharpened with a spark gap if necessary.
Proud Mary, Tue Apr 22 2008, 01:32PM
"The pulsewidth is equal to 2nt Ï„t where nt is the number of turns and Ï„t is the average one way propagation time for a single turn. If t = 0 represents the closing of the switch, the leading edge of the output pulse is delayed by an amount nt Ï„t which for many applications is unimportant."
Source: Fast risetime spiral pulse generator
United States Patent 4140917
For practical purposes, I would reckon on the real life pulse being perhaps twice as long as the theory.
The pulses are triangular, but they could always be sharpened with a spark gap if necessary.
Re: Spiral impulse generator = rolled cap Blumlein induction coil!
Tesladownunder, Wed Apr 23 2008, 08:39AM
I have built a beefier setup.
Specs
Output... bright 1/2 inch (1.25cm) sparks (perhaps 15kV)
Input..... 2.5kV peak. (ie 6 times voltage stepup) (NST 1/2 wave plus 1MOhm for testing).
Foil........ Equal length copper foils 4.5cm x 243cm plus lead in.
Former... 4.2 x 7cm. Ext diameter 6.2cm.
Turns..... Calculated 14 turns
Spark gap 1mm
Core...... Ferrrite E cores to fit in 4cm gap.
Cap....... 20 nF (prev one was 0.9nF)
Insul...... Polyethylene groundsheet
So a better result with more turns and area.
How long the dielectric lasts is unclear and also what increase in input voltage and power will it tolerate? Probably needs to be in oil for that.
TDU
Tesladownunder, Wed Apr 23 2008, 08:39AM
I have built a beefier setup.
Specs
Output... bright 1/2 inch (1.25cm) sparks (perhaps 15kV)
Input..... 2.5kV peak. (ie 6 times voltage stepup) (NST 1/2 wave plus 1MOhm for testing).
Foil........ Equal length copper foils 4.5cm x 243cm plus lead in.
Former... 4.2 x 7cm. Ext diameter 6.2cm.
Turns..... Calculated 14 turns
Spark gap 1mm
Core...... Ferrrite E cores to fit in 4cm gap.
Cap....... 20 nF (prev one was 0.9nF)
Insul...... Polyethylene groundsheet
So a better result with more turns and area.
How long the dielectric lasts is unclear and also what increase in input voltage and power will it tolerate? Probably needs to be in oil for that.
TDU
Re: Spiral impulse generator = rolled cap Blumlein induction coil!
Proud Mary, Wed Apr 23 2008, 10:04AM
Great stuff, TDU.
I have this morning sent off for 75mm adhesive aluminium tape and 100mm insulating tape from ebay suppliers, so I should have a rig of my own to report on in a week or ten days.
I must say how glad I am you dug this up, and gave us all the opportunity to learn something out of the ordinary.
Proud Mary, Wed Apr 23 2008, 10:04AM
Great stuff, TDU.
I have this morning sent off for 75mm adhesive aluminium tape and 100mm insulating tape from ebay suppliers, so I should have a rig of my own to report on in a week or ten days.
I must say how glad I am you dug this up, and gave us all the opportunity to learn something out of the ordinary.
Re: Spiral impulse generator = rolled cap Blumlein induction coil!
Tesladownunder, Wed Apr 23 2008, 10:38AM
It's interesting to go down a new path. I've often wondered about impulse transformers although I guess this is only just one type.
This new version seems to have scaled in spark brightness consistent with 20 times the capacitance and also scaled in output spark length 8mm to 12 mm consistent with the increased turns from 9 to 14. Construction type was similar and dielectric and input voltage were unchanged.
The capacitor holds its charge well and if discharged with a chicken stick giving a reasonable "zap", will give an output spark as well.
I suspect that for high repetition rates, the use of a multiple segment gap would prevent power arcing.
I also suspect from my experience with TEA nitrogen lasers that the spark gap type and position is critical. The use of a gap with two cylindrical electrodes in continuity with each conductor strip and covering the full width should present the lowest inductance.
As it is, I suspect it could be driven much harder than just a few pulses per second, but I am not ready to break it yet.
TDU
Tesladownunder, Wed Apr 23 2008, 10:38AM
It's interesting to go down a new path. I've often wondered about impulse transformers although I guess this is only just one type.
This new version seems to have scaled in spark brightness consistent with 20 times the capacitance and also scaled in output spark length 8mm to 12 mm consistent with the increased turns from 9 to 14. Construction type was similar and dielectric and input voltage were unchanged.
The capacitor holds its charge well and if discharged with a chicken stick giving a reasonable "zap", will give an output spark as well.
I suspect that for high repetition rates, the use of a multiple segment gap would prevent power arcing.
I also suspect from my experience with TEA nitrogen lasers that the spark gap type and position is critical. The use of a gap with two cylindrical electrodes in continuity with each conductor strip and covering the full width should present the lowest inductance.
As it is, I suspect it could be driven much harder than just a few pulses per second, but I am not ready to break it yet.
TDU
Re: Spiral impulse generator = rolled cap Blumlein induction coil!
Proud Mary, Wed Apr 23 2008, 11:11AM
I have seen references to VIG oscillators, where the lines form part of an LC tuned circuit, so it may be possible to drive them quite hard.
My chief concern is about the 'goodness' of the dielectric, on which the velocity of propagation and voltage efficiency depends, not to mention holding off break downs.
If we could sort out the dielectric, almost anyone could achieve hundreds of kV and maybe more with such a simple device. I've noticed, though, that the seemingly more advanced designs often have more complex segmented winding arrangements.
Proud Mary, Wed Apr 23 2008, 11:11AM
I have seen references to VIG oscillators, where the lines form part of an LC tuned circuit, so it may be possible to drive them quite hard.
My chief concern is about the 'goodness' of the dielectric, on which the velocity of propagation and voltage efficiency depends, not to mention holding off break downs.
If we could sort out the dielectric, almost anyone could achieve hundreds of kV and maybe more with such a simple device. I've noticed, though, that the seemingly more advanced designs often have more complex segmented winding arrangements.
Re: Spiral impulse generator = rolled cap Blumlein induction coil!
Dr. Shark, Wed Apr 23 2008, 10:21PM
I redid my VIG with a significantly larger diameter, which as Harry pointed out is supposed to significantly increase the voltage efficiency. I also went for a 1:1 turns ratio with 9 turns each. On my 8cm diameter "core", this gives a D/n of nearly one, so the calculated efficiency should be about 50% without a ferrite core. Going for a much larger former would have improved the efficiency more, but what good would that be if it left me with only 3 turns from my 3m long strips, and therefore a maximum step up ratio of three?
I also redesigned the spark gap for super-low inductance, because apparently the inductance of the "fast side" of the generator is dominated by the switch. The two contacts are not separated by air but by 0.2mm of dielectric, so there is essentially zero loop area between them. Of course this does not allow repetitive operation without burning the dielectric.
Testing the thing immediately showed inter-turn arcing, I should have payed more attention winding the thing (It's getting late, and I am loosing interest in this project). As far as I could tell though, the output spark was still quite weak, most energy being burned in the switching spark gap.
Dr. Shark, Wed Apr 23 2008, 10:21PM
I redid my VIG with a significantly larger diameter, which as Harry pointed out is supposed to significantly increase the voltage efficiency. I also went for a 1:1 turns ratio with 9 turns each. On my 8cm diameter "core", this gives a D/n of nearly one, so the calculated efficiency should be about 50% without a ferrite core. Going for a much larger former would have improved the efficiency more, but what good would that be if it left me with only 3 turns from my 3m long strips, and therefore a maximum step up ratio of three?
I also redesigned the spark gap for super-low inductance, because apparently the inductance of the "fast side" of the generator is dominated by the switch. The two contacts are not separated by air but by 0.2mm of dielectric, so there is essentially zero loop area between them. Of course this does not allow repetitive operation without burning the dielectric.
Testing the thing immediately showed inter-turn arcing, I should have payed more attention winding the thing (It's getting late, and I am loosing interest in this project). As far as I could tell though, the output spark was still quite weak, most energy being burned in the switching spark gap.
Re: Spiral impulse generator = rolled cap Blumlein induction coil!
Proud Mary, Wed Apr 23 2008, 10:37PM
Getting the dielectric just right seems to be everything with this device. I'm sure there must be a source of a suitable material that is cheap and easy to get if only we could think what it was.
I've read several papers where the lines are described as metalized tapes, so I know I have that part right. But I have doubts about my plan to use several thicknesses of 100mm wide insulating tape as the dielectric, because of the difficulty of not trapping any air while I'm winding it with five thumbs.
Kraft paper and oil is always an option, I suppose. It has nothing like the dielectric properties of polyethylene or PTFE, but can be laid on thick and cheap!
Proud Mary, Wed Apr 23 2008, 10:37PM
Dr. Shark wrote ...
Testing the thing immediately showed inter-turn arcing, I should have payed more attention winding the thing (It's getting late, and I am loosing interest in this project). As far as I could tell though, the output spark was still quite weak, most energy being burned in the switching spark gap.
Testing the thing immediately showed inter-turn arcing, I should have payed more attention winding the thing (It's getting late, and I am loosing interest in this project). As far as I could tell though, the output spark was still quite weak, most energy being burned in the switching spark gap.
Getting the dielectric just right seems to be everything with this device. I'm sure there must be a source of a suitable material that is cheap and easy to get if only we could think what it was.
I've read several papers where the lines are described as metalized tapes, so I know I have that part right. But I have doubts about my plan to use several thicknesses of 100mm wide insulating tape as the dielectric, because of the difficulty of not trapping any air while I'm winding it with five thumbs.
Kraft paper and oil is always an option, I suppose. It has nothing like the dielectric properties of polyethylene or PTFE, but can be laid on thick and cheap!
Re: Spiral impulse generator = rolled cap Blumlein induction coil!
Firefox, Thu Apr 24 2008, 01:08AM
What about teflon tape? Its not exactly cheap, but it is an excellent insulator, and you can use relatively small amounts of it to insulate the coils.
Firefox, Thu Apr 24 2008, 01:08AM
What about teflon tape? Its not exactly cheap, but it is an excellent insulator, and you can use relatively small amounts of it to insulate the coils.
Re: Spiral impulse generator = rolled cap Blumlein induction coil!
Proud Mary, Thu Apr 24 2008, 09:13AM
Yes, PTFE would be my first choice, but I have no idea where I might find 100mm wide tape of suitable thickness at a price I could afford. I'm sure it is available from specialist plastic stock suppliers, but having bought PTFE tubes and rods before, I have no doubt it would be expensive.
Proud Mary, Thu Apr 24 2008, 09:13AM
Firefox wrote ...
What about teflon tape? Its not exactly cheap, but it is an excellent insulator, and you can use relatively small amounts of it to insulate the coils.
What about teflon tape? Its not exactly cheap, but it is an excellent insulator, and you can use relatively small amounts of it to insulate the coils.
Yes, PTFE would be my first choice, but I have no idea where I might find 100mm wide tape of suitable thickness at a price I could afford. I'm sure it is available from specialist plastic stock suppliers, but having bought PTFE tubes and rods before, I have no doubt it would be expensive.
Re: Spiral impulse generator = rolled cap Blumlein induction coil!
Dr. Shark, Thu Apr 24 2008, 11:29AM
PTFE would also be advantageous from a loss tangent point of view, apparently the Mylar that I am using is quite lossy, whereas PTFE is one of the best plastic dielectrics. I have no idea where it could be obtained though.
The insulating tape you plan on using is probably going to be PVC, do you know the dielectric properties of that? I think it is not commonly used for capacitors, but I don't know why.
Dr. Shark, Thu Apr 24 2008, 11:29AM
PTFE would also be advantageous from a loss tangent point of view, apparently the Mylar that I am using is quite lossy, whereas PTFE is one of the best plastic dielectrics. I have no idea where it could be obtained though.
The insulating tape you plan on using is probably going to be PVC, do you know the dielectric properties of that? I think it is not commonly used for capacitors, but I don't know why.
Re: Spiral impulse generator = rolled cap Blumlein induction coil!
..., Thu Apr 24 2008, 02:30PM
Not sure how think you need the dialectic, but you can get 6" wide .005" for only $2/ft, 6" bu .010" for $3/ft, and many other sizes in between.
A little pricey, but not completely unrealistic...
..., Thu Apr 24 2008, 02:30PM
Not sure how think you need the dialectic, but you can get 6" wide .005" for only $2/ft, 6" bu .010" for $3/ft, and many other sizes in between.
A little pricey, but not completely unrealistic...
Re: Spiral impulse generator = rolled cap Blumlein induction coil!
Proud Mary, Thu Apr 24 2008, 04:07PM
PVC has a typical dielectric constant of 3, and a dielectric strength between about 550V - 750V/mm.
Mylar has a typical dielectric constant of 3.2, and a dielectric strength of around 7kV/mm, vastly superior.
PTFE has a dielectric constant of around 2.1, a dielectric strength of 500V - 1kV/mm, but up to 5kV/mm in 'modified' PTFE, (almost as good as Mylar) but the dielectric strength per mm declines with increasing thickness for some reason.
I'm don't think my plan to use four thicknesses of PVC inslulating tape is likely work except at low charge voltages, so I shall have to keep an eye out for cheap sources of plastic shim or tape of suitable thickness.
If I were to charge my VIG with 14kV DC (rectified from an old but good 10kV NST) then the dielectric would need to hold off at least 28kV at the far end of the line. Allowing a 50% safety margin, this would mean the dielectric must be good to 42kV - which would be 6mm of Mylar.
I am beginning to understand why people have written about the use of capacitor winding machines in the construction of VIGs, though there are usually ingenious amateur means of getting almost as good results for almost none of the price.
Proud Mary, Thu Apr 24 2008, 04:07PM
Dr. Shark wrote ...
PTFE would also be advantageous from a loss tangent point of view, apparently the Mylar that I am using is quite lossy, whereas PTFE is one of the best plastic dielectrics. I have no idea where it could be obtained though.
The insulating tape you plan on using is probably going to be PVC, do you know the dielectric properties of that? I think it is not commonly used for capacitors, but I don't know why.
PTFE would also be advantageous from a loss tangent point of view, apparently the Mylar that I am using is quite lossy, whereas PTFE is one of the best plastic dielectrics. I have no idea where it could be obtained though.
The insulating tape you plan on using is probably going to be PVC, do you know the dielectric properties of that? I think it is not commonly used for capacitors, but I don't know why.
PVC has a typical dielectric constant of 3, and a dielectric strength between about 550V - 750V/mm.
Mylar has a typical dielectric constant of 3.2, and a dielectric strength of around 7kV/mm, vastly superior.
PTFE has a dielectric constant of around 2.1, a dielectric strength of 500V - 1kV/mm, but up to 5kV/mm in 'modified' PTFE, (almost as good as Mylar) but the dielectric strength per mm declines with increasing thickness for some reason.
I'm don't think my plan to use four thicknesses of PVC inslulating tape is likely work except at low charge voltages, so I shall have to keep an eye out for cheap sources of plastic shim or tape of suitable thickness.
If I were to charge my VIG with 14kV DC (rectified from an old but good 10kV NST) then the dielectric would need to hold off at least 28kV at the far end of the line. Allowing a 50% safety margin, this would mean the dielectric must be good to 42kV - which would be 6mm of Mylar.
I am beginning to understand why people have written about the use of capacitor winding machines in the construction of VIGs, though there are usually ingenious amateur means of getting almost as good results for almost none of the price.
Re: Spiral impulse generator = rolled cap Blumlein induction coil!
Dr. Dark Current, Thu Apr 24 2008, 04:19PM
Dr. Dark Current, Thu Apr 24 2008, 04:19PM
Harry wrote ...
PVC has a typical dielectric constant of 3, and a dielectric strength between about 550V - 750V/mm.
I really doubt that it has lower strength than air. I assume that mains cables etc. and all the wires with thick rubbery insulation are PVC insulated. Once I tried 40kV DC on a wire with some 1mm insulation and it didn't break down.PVC has a typical dielectric constant of 3, and a dielectric strength between about 550V - 750V/mm.
Re: Spiral impulse generator = rolled cap Blumlein induction coil!
Proud Mary, Thu Apr 24 2008, 05:21PM
Forgive me, I am not used to American notation, and misread the American "mil" as being mm in the table I was using. I have now learnt that 1 American mil = 0.0254 millimeters, which seems a very odd figure to use in metrology. The figures I have misquoted above should be read as American 'mils' and my conclusions about them ignored!
Proud Mary, Thu Apr 24 2008, 05:21PM
Plasmaddict wrote ...
Harry wrote ...
PVC has a typical dielectric constant of 3, and a dielectric strength between about 550V - 750V/mm.
I really doubt that it has lower strength than air. I assume that mains cables etc. and all the wires with thick rubbery insulation are PVC insulated. Once I tried 40kV DC on a wire with some 1mm insulation and it didn't break down.PVC has a typical dielectric constant of 3, and a dielectric strength between about 550V - 750V/mm.
Forgive me, I am not used to American notation, and misread the American "mil" as being mm in the table I was using. I have now learnt that 1 American mil = 0.0254 millimeters, which seems a very odd figure to use in metrology. The figures I have misquoted above should be read as American 'mils' and my conclusions about them ignored!
Re: Spiral impulse generator = rolled cap Blumlein induction coil!
Bored Chemist, Thu Apr 24 2008, 05:56PM
Do you folks know one of you was selling one of these spiral thingies?
Bored Chemist, Thu Apr 24 2008, 05:56PM
Do you folks know one of you was selling one of these spiral thingies?
Re: Spiral impulse generator = rolled cap Blumlein induction coil!
Andyman, Thu Apr 24 2008, 07:19PM
Yes, one mil is the same thing as 1 thousandth of an inch or .001 inches. Not millimeter
Andyman, Thu Apr 24 2008, 07:19PM
Yes, one mil is the same thing as 1 thousandth of an inch or .001 inches. Not millimeter
Re: Spiral impulse generator = rolled cap Blumlein induction coil!
jpsmith123, Fri Apr 25 2008, 12:44AM
I looked into these spiral vector-inversion generators a few years ago. I may be wrong, but I ultimately concluded that for voltage pulses of several hundred Kv to a Mv or so, with pulse widths of tens to hundreds of ns, delivering energies of tens to a few hundred joules, an air-core pulse transformer might be a better all-around choice. Yes, the spiral generator has the apparent advantages (over a Marx generator) of cheap construction, small size and a single spark gap switch, but a properly designed and constructed air-core pulse transformer would have the same advantages, I think, and may actually be easier to build and more robust.
jpsmith123, Fri Apr 25 2008, 12:44AM
I looked into these spiral vector-inversion generators a few years ago. I may be wrong, but I ultimately concluded that for voltage pulses of several hundred Kv to a Mv or so, with pulse widths of tens to hundreds of ns, delivering energies of tens to a few hundred joules, an air-core pulse transformer might be a better all-around choice. Yes, the spiral generator has the apparent advantages (over a Marx generator) of cheap construction, small size and a single spark gap switch, but a properly designed and constructed air-core pulse transformer would have the same advantages, I think, and may actually be easier to build and more robust.
Re: Spiral impulse generator = rolled cap Blumlein induction coil!
Proud Mary, Fri Apr 25 2008, 10:25AM
But for the home experimenter, amateur scientist and tinkerer like me, the Vector Inversion Generator is a whole new challenge with new concepts and new skills to master. You might as well tell a radio ham he could buy a better transmitter than he could ever build, so why waste his time in the garden shed with a soldering iron. But that is not what hobbies are all about!
Proud Mary, Fri Apr 25 2008, 10:25AM
jpsmith123 wrote ...
a properly designed and constructed air-core pulse transformer would have the same advantages, I think, and may actually be easier to build and more robust.
a properly designed and constructed air-core pulse transformer would have the same advantages, I think, and may actually be easier to build and more robust.
But for the home experimenter, amateur scientist and tinkerer like me, the Vector Inversion Generator is a whole new challenge with new concepts and new skills to master. You might as well tell a radio ham he could buy a better transmitter than he could ever build, so why waste his time in the garden shed with a soldering iron. But that is not what hobbies are all about!
Re: Spiral impulse generator = rolled cap Blumlein induction coil!
jpsmith123, Fri Apr 25 2008, 11:11AM
I didn't mean to imply that it's not worth tinkering with, if you're so inclined; rather, I was pointing out that if you're building it because you want an inexpensive source of moderately fast HV pulses for some application, an air-core pulse transformer might be better. (And I don't see how your "buying vs building" analogy applies, since you would build the air-core xfrm and in a sense face "a new challenge" there too).
jpsmith123, Fri Apr 25 2008, 11:11AM
I didn't mean to imply that it's not worth tinkering with, if you're so inclined; rather, I was pointing out that if you're building it because you want an inexpensive source of moderately fast HV pulses for some application, an air-core pulse transformer might be better. (And I don't see how your "buying vs building" analogy applies, since you would build the air-core xfrm and in a sense face "a new challenge" there too).
Re: Spiral impulse generator = rolled cap Blumlein induction coil!
Tesladownunder, Sat Apr 26 2008, 08:42AM
Another upgrade with 40% more windings.
Specs
Output... bright 1inch (2.5cm) sparks (perhaps 30kV)
Input..... less than 12kV peak. (ie 3 times voltage stepup) (NST doubled plus 1MOhm).
Foil........ Equal length copper foils 4.5cm x 367cm plus lead in.
Former... 4.2 x 7cm. Ext diameter 8cm.
Turns..... Calculated 20 turns
Spark gap 2mm
Core...... Ferrrite E cores to fit in 4cm gap.
Cap....... 45 nF (prev one was 0.9nF)
Insul...... Polyethylene groundsheet
Arcing over is a problem with higher input voltages and the higher voltage. Anything further would have to be under oil.
I am still a bit uncertain about the 12kV input with voltage doubled NST across the diode and with a series resistor into the capacitance of the generator. It is probably a fair bit lower as the 2mm spark gap is at the limit of working. I will try with a different supply and metering later.
Has anyone else got any spark photos to show?
Peter
Tesladownunder, Sat Apr 26 2008, 08:42AM
Another upgrade with 40% more windings.
Specs
Output... bright 1inch (2.5cm) sparks (perhaps 30kV)
Input..... less than 12kV peak. (ie 3 times voltage stepup) (NST doubled plus 1MOhm).
Foil........ Equal length copper foils 4.5cm x 367cm plus lead in.
Former... 4.2 x 7cm. Ext diameter 8cm.
Turns..... Calculated 20 turns
Spark gap 2mm
Core...... Ferrrite E cores to fit in 4cm gap.
Cap....... 45 nF (prev one was 0.9nF)
Insul...... Polyethylene groundsheet
Arcing over is a problem with higher input voltages and the higher voltage. Anything further would have to be under oil.
I am still a bit uncertain about the 12kV input with voltage doubled NST across the diode and with a series resistor into the capacitance of the generator. It is probably a fair bit lower as the 2mm spark gap is at the limit of working. I will try with a different supply and metering later.
Has anyone else got any spark photos to show?
Peter
Re: Spiral impulse generator = rolled cap Blumlein induction coil!
Proud Mary, Sat Apr 26 2008, 09:17AM
Well done, TDU.
I've sent off by mail order for some aluminium tapes but I haven't sorted out the dielectric yet, which seems to me to be at the heart of the thing.
Proud Mary, Sat Apr 26 2008, 09:17AM
Well done, TDU.
I've sent off by mail order for some aluminium tapes but I haven't sorted out the dielectric yet, which seems to me to be at the heart of the thing.
Re: Spiral impulse generator = rolled cap Blumlein induction coil!
cedric, Thu Sept 02 2010, 09:24AM
does any body have measure the rise time of the secondary pulse?
cedric, Thu Sept 02 2010, 09:24AM
does any body have measure the rise time of the secondary pulse?
Re: Spiral impulse generator = rolled cap Blumlein induction coil!
Proud Mary, Thu Sept 02 2010, 07:45PM
Pulse rise times of well designed vector inversion generators are in the nanosecond regime, but I had no equipment suitable for making these kind of meausrements with the few small VIGs I constructed.
Proud Mary, Thu Sept 02 2010, 07:45PM
cedric wrote ...
does any body have measure the rise time of the secondary pulse?
does any body have measure the rise time of the secondary pulse?
Pulse rise times of well designed vector inversion generators are in the nanosecond regime, but I had no equipment suitable for making these kind of meausrements with the few small VIGs I constructed.
Re: Spiral impulse generator = rolled cap Blumlein induction coil!
Patrick, Thu Sept 02 2010, 08:08PM
Nanosecond rise times are fast, but maybe a well configured CVD with a really good DSO-scope could do it?
If the rise times were 100-200nS im sure it could be done with a specialized set-up. with ferrite i can pretty much say with certainty that the rise times are way slower, so measurement may not be impossible, resistively or capacitivley.
Patrick, Thu Sept 02 2010, 08:08PM
Nanosecond rise times are fast, but maybe a well configured CVD with a really good DSO-scope could do it?
If the rise times were 100-200nS im sure it could be done with a specialized set-up. with ferrite i can pretty much say with certainty that the rise times are way slower, so measurement may not be impossible, resistively or capacitivley.
Re: Spiral impulse generator = rolled cap Blumlein induction coil!
Proud Mary, Thu Sept 02 2010, 09:24PM
The type I was interested in were the true transmission line VIGs, which can have rise times <10ns, according to the literature. With no means of investigation in the time domain, I looked at some of the more accessible properties of these interesting devices.
Proud Mary, Thu Sept 02 2010, 09:24PM
The type I was interested in were the true transmission line VIGs, which can have rise times <10ns, according to the literature. With no means of investigation in the time domain, I looked at some of the more accessible properties of these interesting devices.
Re: Spiral impulse generator = rolled cap Blumlein induction coil!
Patrick, Thu Sept 02 2010, 09:36PM
Patrick, Thu Sept 02 2010, 09:36PM
Proud Mary wrote ...
....which can have rise times <10ns....
wholly crap!....which can have rise times <10ns....
Re: Spiral impulse generator = rolled cap Blumlein induction coil!
Tesladownunder, Fri Sept 03 2010, 12:41AM
I have an analog storage CRO to 100Mhz so can do something to 10ns period theoretically. I wouldnt like to put 30kV anything with a 10ns risetime anywhere near my CRO without some very clever protection circuitry that can respond to this speed and beyond. Not sure that a simple spark gap will cut it.
This generator has now been put away in one of over 100 boxes continaing various projects stacked in my shed, shipping container and lounge....
Tesladownunder, Fri Sept 03 2010, 12:41AM
Patrick wrote ...
Holy crap or wholly crap convey rather different meanings.Proud Mary wrote ...
....which can have rise times <10ns....
wholly crap! ....which can have rise times <10ns....
I have an analog storage CRO to 100Mhz so can do something to 10ns period theoretically. I wouldnt like to put 30kV anything with a 10ns risetime anywhere near my CRO without some very clever protection circuitry that can respond to this speed and beyond. Not sure that a simple spark gap will cut it.
This generator has now been put away in one of over 100 boxes continaing various projects stacked in my shed, shipping container and lounge....
Re: Spiral impulse generator = rolled cap Blumlein induction coil!
Patrick, Fri Sept 03 2010, 01:45AM
I could almost be certain your scope would survive if we did this in person, however if you live in australia and I in california, then maybe a DSO is cheaper then the plane ticket.
Anyway risk is part of scientific advancement.
Patrick, Fri Sept 03 2010, 01:45AM
Tesladownunder wrote ...
Holy crap or wholly crap convey rather different meanings.
Holy crap or wholly crap convey rather different meanings.
Tesladownunder wrote ...
I have an analog storage CRO to 100Mhz so can do something to 10ns period theoretically. I wouldnt like to put 30kV anything with a 10ns risetime anywhere near my CRO without some very clever protection circuitry that can respond to this speed and beyond. Not sure that a simple spark gap will cut it.
This generator has now been put away in one of over 100 boxes continaing various projects stacked in my shed, shipping container and lounge....
I have an analog storage CRO to 100Mhz so can do something to 10ns period theoretically. I wouldnt like to put 30kV anything with a 10ns risetime anywhere near my CRO without some very clever protection circuitry that can respond to this speed and beyond. Not sure that a simple spark gap will cut it.
This generator has now been put away in one of over 100 boxes continaing various projects stacked in my shed, shipping container and lounge....
I could almost be certain your scope would survive if we did this in person, however if you live in australia and I in california, then maybe a DSO is cheaper then the plane ticket.
Anyway risk is part of scientific advancement.
Re: Spiral impulse generator = rolled cap Blumlein induction coil!
Proud Mary, Fri Sept 03 2010, 10:04AM
5.2 ns was the fastest rise time I could find in the literature, in this harmful-sounding device. I see Larry "Doomsday" Altgilbers is one of the authors, whom many here will remember as a co-inventor of the "Gatling Marx Generator" contraption:
Rev. Sci. Instrum. 77, 043904 (2006); doi:10.1063/1.2168674 (5 pages)
Completely explosive ultracompact high-voltage nanosecond pulse-generating system
Sergey I. Shkuratov1, Evgueni F. Talantsev1, Jason Baird1, Millard F. Rose2, Zachary Shotts2, Larry L. Altgilbers3, and Allen H. Stults4
1Loki Inc., Rolla, Missouri 65409
2Radiance Technologies, Inc., Huntsville, Alabama 35807
3U.S. Army Space and Missile Defense Command, Huntsville, Alabama 35807
4U.S. Army Aviation and Missile Research, Development, and Engineering Center, Alabama 35898
(Received 30 October 2005; accepted 2 January 2006; published online 10 April 2006)
A conventional pulsed power technology has been combined with an explosive pulsed power technology to produce an autonomous high-voltage power supply. The power supply contained an explosive-driven high-voltage primary power source and a power-conditioning stage. The ultracompact explosive-driven primary power source was based on the physical effect of shock-wave depolarization of high-energy Pb(Zr52Ti48)O3 ferroelectric material. The volume of the energy-carrying ferroelectric elements in the shock-wave ferroelectric generators (SWFEGs) varied from 1.2 to 2.6 cm3. The power-conditioning stage was based on the spiral vector inversion generator (VIG). The SWFEG-VIG system demonstrated successful operation and good performance. The amplitude of the output voltage pulse of the SWFEG-VIG system exceeded 90 kV, with a rise time of 5.2 ns.
© 2006 American Institute of Physics
Proud Mary, Fri Sept 03 2010, 10:04AM
5.2 ns was the fastest rise time I could find in the literature, in this harmful-sounding device. I see Larry "Doomsday" Altgilbers is one of the authors, whom many here will remember as a co-inventor of the "Gatling Marx Generator" contraption:
Rev. Sci. Instrum. 77, 043904 (2006); doi:10.1063/1.2168674 (5 pages)
Completely explosive ultracompact high-voltage nanosecond pulse-generating system
Sergey I. Shkuratov1, Evgueni F. Talantsev1, Jason Baird1, Millard F. Rose2, Zachary Shotts2, Larry L. Altgilbers3, and Allen H. Stults4
1Loki Inc., Rolla, Missouri 65409
2Radiance Technologies, Inc., Huntsville, Alabama 35807
3U.S. Army Space and Missile Defense Command, Huntsville, Alabama 35807
4U.S. Army Aviation and Missile Research, Development, and Engineering Center, Alabama 35898
(Received 30 October 2005; accepted 2 January 2006; published online 10 April 2006)
A conventional pulsed power technology has been combined with an explosive pulsed power technology to produce an autonomous high-voltage power supply. The power supply contained an explosive-driven high-voltage primary power source and a power-conditioning stage. The ultracompact explosive-driven primary power source was based on the physical effect of shock-wave depolarization of high-energy Pb(Zr52Ti48)O3 ferroelectric material. The volume of the energy-carrying ferroelectric elements in the shock-wave ferroelectric generators (SWFEGs) varied from 1.2 to 2.6 cm3. The power-conditioning stage was based on the spiral vector inversion generator (VIG). The SWFEG-VIG system demonstrated successful operation and good performance. The amplitude of the output voltage pulse of the SWFEG-VIG system exceeded 90 kV, with a rise time of 5.2 ns.
© 2006 American Institute of Physics
Re: Spiral impulse generator = rolled cap Blumlein induction coil!
Superkuh, Fri Oct 28 2011, 11:53PM
[Oops. Nope]
Sorry to dig up such a long dead thread, but while reading about the development of the steamer chambers at the Standford Linear Accelerator I found a very interesting appendix about a type of spiral impulse generator using 0.002-to-0.005 ~inch copper foil cut to a double tabpe and attached to a sheet of polyethylene or mylar insulation with ~15-20 turns with max widths (b_max) of the copper foils from 10 to 60cm. Normal.
But...It is abnormal in that the detail construction diagrams and instructions call for the addition of a copper sulfate soaked toilet paper layer around the tapered edges left open by the copper. These are soaked in the CuSO4 and then the water removed under vacuum leaving the copper sulfate precipitate. This is over tens of minutes. Claims of less edge breakdown and edge voltage gradient are suggested. Performance is very good.
]vector- inversion_autotransformers_design__jc_martin__i_sm ith.pdf[/file]
Superkuh, Fri Oct 28 2011, 11:53PM
[Oops. Nope]
Sorry to dig up such a long dead thread, but while reading about the development of the steamer chambers at the Standford Linear Accelerator I found a very interesting appendix about a type of spiral impulse generator using 0.002-to-0.005 ~inch copper foil cut to a double tabpe and attached to a sheet of polyethylene or mylar insulation with ~15-20 turns with max widths (b_max) of the copper foils from 10 to 60cm. Normal.
But...It is abnormal in that the detail construction diagrams and instructions call for the addition of a copper sulfate soaked toilet paper layer around the tapered edges left open by the copper. These are soaked in the CuSO4 and then the water removed under vacuum leaving the copper sulfate precipitate. This is over tens of minutes. Claims of less edge breakdown and edge voltage gradient are suggested. Performance is very good.
]vector- inversion_autotransformers_design__jc_martin__i_sm ith.pdf[/file]
Re: Spiral impulse generator = rolled cap Blumlein induction coil!
jpsmith123, Sat Oct 29 2011, 01:46PM
The device shown is actually a transformer - a spiral strip transformer (in this case an autotransformer), which looks similar to a spiral vector inversion generator but isn't.
jpsmith123, Sat Oct 29 2011, 01:46PM
The device shown is actually a transformer - a spiral strip transformer (in this case an autotransformer), which looks similar to a spiral vector inversion generator but isn't.
Print this page