Need 30 kilovolts!
Oneironaut, Wed May 16 2012, 02:40AMIn a new project I am doing, I find myself needing a 30kv or better power supply. Endless surplus searching has revealed nothing, but I do have a good supply of pole transformers at the local scrap yard. From my understanding, there would all connect to 14.440kv and step down to 240 volts? If this is the case, I should be able to connect the center tap to 240 volts and have the transformer output 28kv then.
Does this sound feasible?
Brad
Re: Need 30 kilovolts!
genious 7, Wed May 16 2012, 02:51AM
What kind of amperage do you need?
genious 7, Wed May 16 2012, 02:51AM
What kind of amperage do you need?
Re: Need 30 kilovolts!
Oneironaut, Wed May 16 2012, 02:56AM
Not much really. I am going to charge a large capacitor bank, and am willing to simply wait longer.
I had a 30kv polepig last time, but had to toss it as it was too large to take when I moved. Wish I still had it.
Brad
Oneironaut, Wed May 16 2012, 02:56AM
Not much really. I am going to charge a large capacitor bank, and am willing to simply wait longer.
I had a 30kv polepig last time, but had to toss it as it was too large to take when I moved. Wish I still had it.
Brad
Re: Need 30 kilovolts!
Luceš, Wed May 16 2012, 03:14AM
Why Not use a zvs flyback driver?
Luceš, Wed May 16 2012, 03:14AM
Why Not use a zvs flyback driver?
Re: Need 30 kilovolts!
teravolt, Wed May 16 2012, 03:51AM
how much capacitance and what kind of capacitor are you charging? how many joules. if your cap is big a 240 to 14.440k into a full wave dublier would work. If your bank is small and portable a zvs ie flyback circuit might be more practical
teravolt, Wed May 16 2012, 03:51AM
how much capacitance and what kind of capacitor are you charging? how many joules. if your cap is big a 240 to 14.440k into a full wave dublier would work. If your bank is small and portable a zvs ie flyback circuit might be more practical
Re: Need 30 kilovolts!
Mattski, Wed May 16 2012, 05:55AM
If you want something that you can just buy then Information Unlimited has some, no idea what the quality is.
You shouldn't apply 240 across one output to the center tap of a pole transformer, that'll probably saturate the core, it's only designed for half that many volts per turn.
Mattski, Wed May 16 2012, 05:55AM
If you want something that you can just buy then Information Unlimited has some, no idea what the quality is.
You shouldn't apply 240 across one output to the center tap of a pole transformer, that'll probably saturate the core, it's only designed for half that many volts per turn.
Re: Need 30 kilovolts!
Dr. Slack, Wed May 16 2012, 07:11AM
If by center tap you mean the winding normally outputting 120v in step-down duty then NO, it is not feasible. You can abuse transformers and get away with it with over-current and over-power, but you cannot do that for over-voltage.
You can connect the 240v output winding to your 240v supply, and get 14kV on the HV winding. If your final output is destined to be DC, then rectify with a voltage doubler instead of a bridge. If you want AC, tough.
Dr. Slack, Wed May 16 2012, 07:11AM
Oneironaut wrote ...
... From my understanding, there would all connect to 14.440kv and step down to 240 volts? If this is the case, I should be able to connect the center tap to 240 volts and have the transformer output 28kv then.
Does this sound feasible?
... From my understanding, there would all connect to 14.440kv and step down to 240 volts? If this is the case, I should be able to connect the center tap to 240 volts and have the transformer output 28kv then.
Does this sound feasible?
If by center tap you mean the winding normally outputting 120v in step-down duty then NO, it is not feasible. You can abuse transformers and get away with it with over-current and over-power, but you cannot do that for over-voltage.
You can connect the 240v output winding to your 240v supply, and get 14kV on the HV winding. If your final output is destined to be DC, then rectify with a voltage doubler instead of a bridge. If you want AC, tough.
Re: Need 30 kilovolts!
Oneironaut, Wed May 16 2012, 02:16PM
Thanks for the input.
I think a flyback may be too small for my project. When I used the pole pig here, I had connected the 120v winding to 120v AC to charge my caps, but this transformer was an oddity, rated at almost 40kv...
http://lucidscience.com/gal-rock%20disaggregator-18.aspx
Yes, I need DC, and last time used a string of 16 HV diodes. There are a dozen pole pigs sitting at the local scrapyard, and the transformers inside the can are larger than the one I used shown here and have dual windings on the core. The plates have been removed though, so I have no idea what they are rated for.
Worst case scenario would probably be 14kv, I guess.
I ballasted my last pole pig using 4 stove elements in parallel, and that worked fine for the ~5 minutes I needed it outputting HV. I know it would be suboptimal to pump 240 into the 120 winding, but for intermittent capacitor charging duty, it seems doable in theory.
Another idea would be to acquire 2 of the pole transformers and run their 240 sides in parallel, tying the 14kv outputs in series to obtain 28kv. I have done this with MOTs, so I know that works, but that's a lot of weight on my wooden shop floor!
I guess trying it will reveal the answer - it always does, one way or the other.
Brad
Oneironaut, Wed May 16 2012, 02:16PM
Thanks for the input.
I think a flyback may be too small for my project. When I used the pole pig here, I had connected the 120v winding to 120v AC to charge my caps, but this transformer was an oddity, rated at almost 40kv...
http://lucidscience.com/gal-rock%20disaggregator-18.aspx
Yes, I need DC, and last time used a string of 16 HV diodes. There are a dozen pole pigs sitting at the local scrapyard, and the transformers inside the can are larger than the one I used shown here and have dual windings on the core. The plates have been removed though, so I have no idea what they are rated for.
Worst case scenario would probably be 14kv, I guess.
I ballasted my last pole pig using 4 stove elements in parallel, and that worked fine for the ~5 minutes I needed it outputting HV. I know it would be suboptimal to pump 240 into the 120 winding, but for intermittent capacitor charging duty, it seems doable in theory.
Another idea would be to acquire 2 of the pole transformers and run their 240 sides in parallel, tying the 14kv outputs in series to obtain 28kv. I have done this with MOTs, so I know that works, but that's a lot of weight on my wooden shop floor!
I guess trying it will reveal the answer - it always does, one way or the other.
Brad
Re: Need 30 kilovolts!
teravolt, Wed May 16 2012, 04:20PM
if you take them out of the oil and its can it may not hold off the voltage any more
teravolt, Wed May 16 2012, 04:20PM
if you take them out of the oil and its can it may not hold off the voltage any more
Re: Need 30 kilovolts!
Erlend^SE, Wed May 16 2012, 04:34PM
a CW-multiplier circuit driven off a MOT may do the trick?
(I assume you already know the dangers of doing it)
Erlend^SE, Wed May 16 2012, 04:34PM
a CW-multiplier circuit driven off a MOT may do the trick?
(I assume you already know the dangers of doing it)
Re: Need 30 kilovolts!
Oneironaut, Wed May 16 2012, 06:29PM
In the link posted (see video), I ran the pole pig out of the oil constantly without any issue. I could hear it hissing, but no arcs ever occurred in the coils.
Just had another crazy idea.
Run a pair of series MOTs with 240 rather than 120. In "theory", I would get an output of around 8-10kv. Add a CW, and I may be able to pump out 20-30kv from it. It may not work, but for the cost of the parts, I would be willing to give it a try.
I am going to the yard to take photos of those pole pigs and maybe someone here knowledgeable in power transmission hardware could advise as to their possible output.
Brad
Oneironaut, Wed May 16 2012, 06:29PM
In the link posted (see video), I ran the pole pig out of the oil constantly without any issue. I could hear it hissing, but no arcs ever occurred in the coils.
Just had another crazy idea.
Run a pair of series MOTs with 240 rather than 120. In "theory", I would get an output of around 8-10kv. Add a CW, and I may be able to pump out 20-30kv from it. It may not work, but for the cost of the parts, I would be willing to give it a try.
I am going to the yard to take photos of those pole pigs and maybe someone here knowledgeable in power transmission hardware could advise as to their possible output.
Brad
Re: Need 30 kilovolts!
Ben Solon, Wed May 16 2012, 07:56PM
that "hissing" is corona discharge. had you run it any longer, the insulation would have been burned through by the corona, then a nice hot 14kva arc would have been ignited inside the coil.
Ben Solon, Wed May 16 2012, 07:56PM
that "hissing" is corona discharge. had you run it any longer, the insulation would have been burned through by the corona, then a nice hot 14kva arc would have been ignited inside the coil.
Re: Need 30 kilovolts!
Oneironaut, Wed May 16 2012, 09:04PM
I ran it that way for several months, charging the five 50kv caps about once every 10 seconds for hours at a time. The only arc issues I had was on the first version of my hand wound inductors. Heat was also never any issue whatsoever. Ok, the stove coils (ballast) became warm after some use, but never the caps or transformer. Other than blowing up the diode array and the vessel (multiple times), never had any problems.
Brad
Oneironaut, Wed May 16 2012, 09:04PM
ben123324 wrote ...
that "hissing" is corona discharge. had you run it any longer, the insulation would have been burned through by the corona, then a nice hot 14kva arc would have been ignited inside the coil.
that "hissing" is corona discharge. had you run it any longer, the insulation would have been burned through by the corona, then a nice hot 14kva arc would have been ignited inside the coil.
I ran it that way for several months, charging the five 50kv caps about once every 10 seconds for hours at a time. The only arc issues I had was on the first version of my hand wound inductors. Heat was also never any issue whatsoever. Ok, the stove coils (ballast) became warm after some use, but never the caps or transformer. Other than blowing up the diode array and the vessel (multiple times), never had any problems.
Brad
Re: Need 30 kilovolts!
teravolt, Thu May 17 2012, 02:06AM
how fast do you want to charge? why not use a cuple of 15kv neons in parallel with a dublier circuit. the neon transformer would do the current limitting for the diodes. how much capacitance are you charging?
teravolt, Thu May 17 2012, 02:06AM
how fast do you want to charge? why not use a cuple of 15kv neons in parallel with a dublier circuit. the neon transformer would do the current limitting for the diodes. how much capacitance are you charging?
Re: Need 30 kilovolts!
klugesmith, Thu May 17 2012, 02:30AM
Hi Brad.
That's the second time you've talked about operating power transformers at 2x their rated voltage.
Now I generally applaud anyone who reports experimental results here.
But here is a small-scale teaching experiment about core saturation.
It may save you some time and expense, before you try to double-volt a MOT or pole pig.
Take a small 120V-input transformer, such as one made for low voltage lighting / lawn sprinkler control / doorbell etc.
Know its rated maximum primary current.
Then with its secondary unloaded, measure and chart the primary current
as you progressively increase the primary voltage beyond the nameplate rating.
If you are in the US and have split 240V electricity, but no 240V variac,
you could cover the range of interest with a 120V variac on one side of a 240V circuit.
Magnetic flux in the core depends on voltage and frequency, not current.
At rated voltage, the magnetizing current (no-load primary current) is a tiny fraction of
full-load current. (Well, a significant fraction in the case of MOT's and XRT's).
Approaching saturation, the I vs V curve turns upward like an exponential hockey stick.
Usually before 150% of rated voltage, it will surpass the rated full-load current.
If you put 240 VAC (unballasted) on a 120 VAC winding, it's like putting DC on the winding.
Unless you blow a fuse, trip the breaker, or melt the lead-in wire,
the primary will burn out in a matter of seconds, if not sooner.
[edit] Of course you can limit the 240V current to a tolerable value
with a ballast device in series. Then you will get much less than
240V RMS across the primary -- even with no load on the secondary.
The voltage waveforms will be highly distorted (not sinusoidal).
On the brighter side:
Compared to sinusoidal operation, at a given large value of true-RMS primary current:
double-V supply with resistive ballast can get maybe 20% more RMS voltage
and maybe 2x the peak voltage. Maybe that's just what you need!
This can be explored with your small 120V transformer,
on 240V circuit with light bulbs for ballast.
Have fun!
klugesmith, Thu May 17 2012, 02:30AM
Oneironaut wrote ...
Run a pair of series MOTs with 240 rather than 120. In "theory", I would get an output of around 8-10kv. Add a CW, and I may be able to pump out 20-30kv from it. It may not work, but for the cost of the parts, I would be willing to give it a try.
Run a pair of series MOTs with 240 rather than 120. In "theory", I would get an output of around 8-10kv. Add a CW, and I may be able to pump out 20-30kv from it. It may not work, but for the cost of the parts, I would be willing to give it a try.
Hi Brad.
That's the second time you've talked about operating power transformers at 2x their rated voltage.
Now I generally applaud anyone who reports experimental results here.
But here is a small-scale teaching experiment about core saturation.
It may save you some time and expense, before you try to double-volt a MOT or pole pig.
Take a small 120V-input transformer, such as one made for low voltage lighting / lawn sprinkler control / doorbell etc.
Know its rated maximum primary current.
Then with its secondary unloaded, measure and chart the primary current
as you progressively increase the primary voltage beyond the nameplate rating.
If you are in the US and have split 240V electricity, but no 240V variac,
you could cover the range of interest with a 120V variac on one side of a 240V circuit.
Magnetic flux in the core depends on voltage and frequency, not current.
At rated voltage, the magnetizing current (no-load primary current) is a tiny fraction of
full-load current. (Well, a significant fraction in the case of MOT's and XRT's).
Approaching saturation, the I vs V curve turns upward like an exponential hockey stick.
Usually before 150% of rated voltage, it will surpass the rated full-load current.
If you put 240 VAC (unballasted) on a 120 VAC winding, it's like putting DC on the winding.
Unless you blow a fuse, trip the breaker, or melt the lead-in wire,
the primary will burn out in a matter of seconds, if not sooner.
[edit] Of course you can limit the 240V current to a tolerable value
with a ballast device in series. Then you will get much less than
240V RMS across the primary -- even with no load on the secondary.
The voltage waveforms will be highly distorted (not sinusoidal).
On the brighter side:
Compared to sinusoidal operation, at a given large value of true-RMS primary current:
double-V supply with resistive ballast can get maybe 20% more RMS voltage
and maybe 2x the peak voltage. Maybe that's just what you need!
This can be explored with your small 120V transformer,
on 240V circuit with light bulbs for ballast.
Have fun!
Re: Need 30 kilovolts!
Dr. Slack, Thu May 17 2012, 07:21AM
What just about works with MOTs doesn't necessarily with higher voltages. It depends how you series those 14kV outputs.
If you put both their grounds to ground, antiphase the primaries, and get 28kV balanced out of the two hot terminals, then it's perfectly feasible. However, you can get exactly the same output voltage from a rectifying charge pump whether you use one or both secondaries arranged like this, just different amunts of output current, so it's not worth doing.
If you lift the ground of the second secondary, and connect it to the hot of the first, to get 28kV with respect to ground on the second output, then you are asking for trouble. You can lift the ground of a MOT secondary, because the standard winding to core insulation that has to be there anyway for mechanical and transient protection is good enough to stand off several kV. The winding to core insulation of your second secondary may not be able to stand off the full peak 20kV from the first. It might, like the MOT, be only good enough for several kV, maybe even 10? You could try it and see, but stand well back.
+1 with Kluge's observations that if you current limit an over-volted primary, the sharp edges that you get as the primary goes in and out of saturation may give you 2x voltage spikes at the output, which may be all you need for a cap charger. However, you could get away with this in a MOT, 2x overvoltage on 3kV is only 3kv extra for the hot to core insulation. You may run into trouble if you subject your secondaries to an extra unexpected 20kV peak, or you might be OK. Stand well back if you try it.
Dr. Slack, Thu May 17 2012, 07:21AM
Another idea would be to acquire 2 of the pole transformers and run their 240 sides in parallel, tying the 14kv outputs in series to obtain 28kv. I have done this with MOTs, so I know that works, but that's a lot of weight on my wooden shop floor!
What just about works with MOTs doesn't necessarily with higher voltages. It depends how you series those 14kV outputs.
If you put both their grounds to ground, antiphase the primaries, and get 28kV balanced out of the two hot terminals, then it's perfectly feasible. However, you can get exactly the same output voltage from a rectifying charge pump whether you use one or both secondaries arranged like this, just different amunts of output current, so it's not worth doing.
If you lift the ground of the second secondary, and connect it to the hot of the first, to get 28kV with respect to ground on the second output, then you are asking for trouble. You can lift the ground of a MOT secondary, because the standard winding to core insulation that has to be there anyway for mechanical and transient protection is good enough to stand off several kV. The winding to core insulation of your second secondary may not be able to stand off the full peak 20kV from the first. It might, like the MOT, be only good enough for several kV, maybe even 10? You could try it and see, but stand well back.
+1 with Kluge's observations that if you current limit an over-volted primary, the sharp edges that you get as the primary goes in and out of saturation may give you 2x voltage spikes at the output, which may be all you need for a cap charger. However, you could get away with this in a MOT, 2x overvoltage on 3kV is only 3kv extra for the hot to core insulation. You may run into trouble if you subject your secondaries to an extra unexpected 20kV peak, or you might be OK. Stand well back if you try it.
Re: Need 30 kilovolts!
Oneironaut, Thu May 17 2012, 02:28PM
Thanks again for all the advice. This community is a great source of information.
The caps I want to charge will be in a Marx configuration - 5 of them rated at 1uF and 50Kv.
I am going to take a few photos of the internals of those scrap yard polepigs in hopes someone will be able to identify their type, but so far I am swaying towards a 6 stack MOT now. Found a few great threads on the, here.
Thanks.
Brad
Oneironaut, Thu May 17 2012, 02:28PM
Thanks again for all the advice. This community is a great source of information.
The caps I want to charge will be in a Marx configuration - 5 of them rated at 1uF and 50Kv.
I am going to take a few photos of the internals of those scrap yard polepigs in hopes someone will be able to identify their type, but so far I am swaying towards a 6 stack MOT now. Found a few great threads on the, here.
Thanks.
Brad
Re: Need 30 kilovolts!
Tetris, Fri May 18 2012, 09:36PM
connect 2 15kv nsts in series
Tetris, Fri May 18 2012, 09:36PM
connect 2 15kv nsts in series
Re: Need 30 kilovolts!
Thomas W, Fri May 18 2012, 09:38PM
HVC, putting NSTs in series is a dangerous idea, to do so means that both cases will be live and they will die from corona issues quickly from what i know.
Thomas W, Fri May 18 2012, 09:38PM
HVC, putting NSTs in series is a dangerous idea, to do so means that both cases will be live and they will die from corona issues quickly from what i know.
Re: Need 30 kilovolts!
Oneironaut, Sat May 19 2012, 02:32AM
I went back to the scrap yard to have a look at those polepigs again. There is a nice little guy in the back no larger than a garbage can with a single HV terminal. No doubt, a single residential unit rated at 14.440kv input. There were also a bunch of big piggies standing about 4 feet tall with markings of 7200x14400 on the cans. What would the 7200 part mean?
I may just grab the 2 smaller ones as the cases even look repairable. You can never have enough pole pigs in the garage!
Brad
Oneironaut, Sat May 19 2012, 02:32AM
I went back to the scrap yard to have a look at those polepigs again. There is a nice little guy in the back no larger than a garbage can with a single HV terminal. No doubt, a single residential unit rated at 14.440kv input. There were also a bunch of big piggies standing about 4 feet tall with markings of 7200x14400 on the cans. What would the 7200 part mean?
I may just grab the 2 smaller ones as the cases even look repairable. You can never have enough pole pigs in the garage!
Brad
Re: Need 30 kilovolts!
Thomas W, Sat May 19 2012, 12:04PM
wow, nice!
i so want a lil piggie or PT
Thomas W, Sat May 19 2012, 12:04PM
wow, nice!
i so want a lil piggie or PT
Re: Need 30 kilovolts!
Dr. Brownout, Sat May 19 2012, 04:32PM
The 7200 is a tap position. That transformer could be run with 7.2kV or 14.4kV on the high side. Some are rated for only one voltage and others can be used at different voltages.
I would becareful if those transformer are left open like that there are many things that can get into them besides water, bugs like to get in there and arc every once in awhile. So just make sure you clean them good before you use them.
If used dry (without oil) it could ruin them. In oil I have seen them repair themselves by having the puncture swell closed due to the oil being absorbed in to the paper insulation and having the hole swell shut.
--Brian
Dr. Brownout, Sat May 19 2012, 04:32PM
The 7200 is a tap position. That transformer could be run with 7.2kV or 14.4kV on the high side. Some are rated for only one voltage and others can be used at different voltages.
I would becareful if those transformer are left open like that there are many things that can get into them besides water, bugs like to get in there and arc every once in awhile. So just make sure you clean them good before you use them.
If used dry (without oil) it could ruin them. In oil I have seen them repair themselves by having the puncture swell closed due to the oil being absorbed in to the paper insulation and having the hole swell shut.
--Brian
Re: Need 30 kilovolts!
Oneironaut, Sat May 19 2012, 04:50PM
Interesting - following the NST advice here, I did some online shopping and it seems I can purchase a new 15kv NST for under $150...
I could run a pair of these in series and end up with 30kv for under $300! This is less than the yard will charge me to load up the 14kv pole pig.
Interesting.
Brad
Oneironaut, Sat May 19 2012, 04:50PM
Interesting - following the NST advice here, I did some online shopping and it seems I can purchase a new 15kv NST for under $150...
I could run a pair of these in series and end up with 30kv for under $300! This is less than the yard will charge me to load up the 14kv pole pig.
Interesting.
Brad
Re: Need 30 kilovolts!
Thomas W, Sat May 19 2012, 04:57PM
As i said, i really do not recommend seriesing NSTs, they will burn out from what i have heard and many sites say not to do so
Thomas W, Sat May 19 2012, 04:57PM
As i said, i really do not recommend seriesing NSTs, they will burn out from what i have heard and many sites say not to do so
Re: Need 30 kilovolts!
Pinky's Brain, Sat May 19 2012, 06:00PM
How much capacitance do you have to charge and how fast BTW?
Pinky's Brain, Sat May 19 2012, 06:00PM
Oneironaut wrote ...
I think a flyback may be too small for my project. When I used the pole pig here, I had connected the 120v winding to 120v AC to charge my caps, but this transformer was an oddity, rated at almost 40kv...
Just curious, what happened to it?I think a flyback may be too small for my project. When I used the pole pig here, I had connected the 120v winding to 120v AC to charge my caps, but this transformer was an oddity, rated at almost 40kv...
How much capacitance do you have to charge and how fast BTW?
Re: Need 30 kilovolts!
Oneironaut, Sat May 19 2012, 06:15PM
Ok, thanks for the advice on the dual NST.
The pole pig was scrapped when I moved. I actually had 2 of them and did not want the hassle of loading them. The caps are 1uF 50Kv and there are 5 of them in a Marx setup. Charging speed will not be important, but the reversed pole xformer did it in about 10 seconds.
Brad
Oneironaut, Sat May 19 2012, 06:15PM
Ok, thanks for the advice on the dual NST.
The pole pig was scrapped when I moved. I actually had 2 of them and did not want the hassle of loading them. The caps are 1uF 50Kv and there are 5 of them in a Marx setup. Charging speed will not be important, but the reversed pole xformer did it in about 10 seconds.
Brad
Re: Need 30 kilovolts!
Newton Brawn, Sun May 20 2012, 09:53PM
If you apply 240 across one 120V primary output to the center tap of a pole transformer, it saturate the core, the current at 240V line increases like a rocket and
PUFFF !
The 240 line breaker trip or the 120V cable burns.
or even nice dammage.
Also if you drainned the oil from the tranformer tank, the insulation is compromized, the pig may work at 14-28 kV, BUT not suitable to deal with impulses..
Remember that pigs are designed to survive to 115~250kV impulses.
Look in that junkyard for a potential transformer (PT) used in high voltage metering or even in switchgear, normaly the primary is 110V, secondary 14, 18, or 23 kV. It is a dry transformer., 300~500W CONTINUOUSLY .
I saw the pictures of your scrap yard, Im sure they have severals PT.
Good look
Newton Brawn, Sun May 20 2012, 09:53PM
If you apply 240 across one 120V primary output to the center tap of a pole transformer, it saturate the core, the current at 240V line increases like a rocket and
PUFFF !
The 240 line breaker trip or the 120V cable burns.
or even nice dammage.
Also if you drainned the oil from the tranformer tank, the insulation is compromized, the pig may work at 14-28 kV, BUT not suitable to deal with impulses..
Remember that pigs are designed to survive to 115~250kV impulses.
Look in that junkyard for a potential transformer (PT) used in high voltage metering or even in switchgear, normaly the primary is 110V, secondary 14, 18, or 23 kV. It is a dry transformer., 300~500W CONTINUOUSLY .
I saw the pictures of your scrap yard, Im sure they have severals PT.
Good look
Re: Need 30 kilovolts!
Oneironaut, Mon May 21 2012, 03:05AM
Hey, thanks for the tip on the potential transformer. This is the first time I have heard the term, and it seems as though this item is the absolute perfect balance between an NST and pole pig. Large and robust enough for Marx, Tesla, and cap charging work yet not so damn big I need to unload it with an engine lift!
Unless I am reading this plate incorrectly, I should get 22kv out with an input of 110v?...
I think you solved my sourcing problem here!
Brad
Oneironaut, Mon May 21 2012, 03:05AM
Hey, thanks for the tip on the potential transformer. This is the first time I have heard the term, and it seems as though this item is the absolute perfect balance between an NST and pole pig. Large and robust enough for Marx, Tesla, and cap charging work yet not so damn big I need to unload it with an engine lift!
Unless I am reading this plate incorrectly, I should get 22kv out with an input of 110v?...
I think you solved my sourcing problem here!
Brad
Re: Need 30 kilovolts!
Thomas W, Mon May 21 2012, 05:31AM
that is correct, and damn your lucky! i want one of those
Thomas W, Mon May 21 2012, 05:31AM
that is correct, and damn your lucky! i want one of those
Re: Need 30 kilovolts!
Newton Brawn, Mon May 21 2012, 10:58PM
Ok , your PT is complying 100% with my specification...
CongratulationS!
Send more pictures so we can confirm other details.
Of shore, you apply 110V at primary and get 22000V at secondary.
22kV inputing a rectifier/capacitor provide 31kilovolts as required....
NOTE THAT THE SECONDARY CONTINUOUSLY CURRENT IS ONLY 22MILIAMPERES, maybe 100mA for 2-3 minutes.
Allway connect the primary to 110V supply with a resistor of 27 ohms, 400W IN SERIES in order to limit the secondary to 22 mA, protecting the windings. For a short time less than 2 minutes you may use a 6 ohms resistor ...
The resistor 27ohms, 400W may be four 110V 100W light bulbs
The best will be a homemade variable reactor rated 110V. 3A. 5-27ohms. If you have a MOT (microwave ovem transformer) it cam be modified to result in a nice variable reactor.. Let me know !
Regards
Newton
EDIT ! Was this PT storaged in a wet place??? or just lay down in the weather?? throw in the backyard ?
If the moisture reached inside the secondary winding the PT will fail >> PUFF !
Good practice is dry complete before apply 110 volts in the primary. Leave it with a 110V 100W enclosed in a box for 2-3 days, measure the dc resistence with a ohmiter and let me kow.
Other practice is provide a good and effective shot circuit art the secondary terminals and apply 110V VIA 27OHM SERIAL RESISTOR, for 2-3 days. The windings will warm up cleaning the moisture.
Newton Brawn, Mon May 21 2012, 10:58PM
Ok , your PT is complying 100% with my specification...
CongratulationS!
Send more pictures so we can confirm other details.
Of shore, you apply 110V at primary and get 22000V at secondary.
22kV inputing a rectifier/capacitor provide 31kilovolts as required....
NOTE THAT THE SECONDARY CONTINUOUSLY CURRENT IS ONLY 22MILIAMPERES, maybe 100mA for 2-3 minutes.
Allway connect the primary to 110V supply with a resistor of 27 ohms, 400W IN SERIES in order to limit the secondary to 22 mA, protecting the windings. For a short time less than 2 minutes you may use a 6 ohms resistor ...
The resistor 27ohms, 400W may be four 110V 100W light bulbs
The best will be a homemade variable reactor rated 110V. 3A. 5-27ohms. If you have a MOT (microwave ovem transformer) it cam be modified to result in a nice variable reactor.. Let me know !
Regards
Newton
EDIT ! Was this PT storaged in a wet place??? or just lay down in the weather?? throw in the backyard ?
If the moisture reached inside the secondary winding the PT will fail >> PUFF !
Good practice is dry complete before apply 110 volts in the primary. Leave it with a 110V 100W enclosed in a box for 2-3 days, measure the dc resistence with a ohmiter and let me kow.
Other practice is provide a good and effective shot circuit art the secondary terminals and apply 110V VIA 27OHM SERIAL RESISTOR, for 2-3 days. The windings will warm up cleaning the moisture.
Re: Need 30 kilovolts!
brandon3055, Wed May 23 2012, 03:45AM
Newton can you leave a link to a sight explaining how to modify an MOT into a veriable reactor thanks
brandon3055, Wed May 23 2012, 03:45AM
Newton can you leave a link to a sight explaining how to modify an MOT into a veriable reactor thanks
Re: Need 30 kilovolts!
Newton Brawn, Thu May 24 2012, 03:26AM
Hi!
The alternating current reactor, also know as ballast, inductor, or even a inductance, is a coil with a magnetic core that has a small air gap.
The MOT primary coil normally is rated 5-10 amper, and the number of primary turns (120~180). This is enough to allows the core works bellow the iron saturation area when 120Vac is applied. So, the primary coil as is is suitable to work, without any modification.
Then we need to provide a air gap is adjustable (0.1 ~3.0mm) between the E and I cores. The result is a variable reluctance to the magnetic flow and a variable inductance. In this applicationthe the final effect is similar to a reostat in serie with the PT primary, allowing adjustment in the primary ac current.
The MOT modification consist in open the transformer magnetic core, remove the high voltage coil, close the core leaving a small air gap between the I and E core. In order to get good and practical core closing, the air gap may be filled up with a hard cardboard, plastic sheet, fiber material.
A tutorial explaining how to open the transformer the may be found in the site:
or read the thread "windings in a mot" , posted on march 31 2012.
(be more carefull to avoid any damage in the primary coil.)
I'd like see your solution how to provide a mechanic variation of the gap.
Regards
Newton
Newton Brawn, Thu May 24 2012, 03:26AM
Hi!
The alternating current reactor, also know as ballast, inductor, or even a inductance, is a coil with a magnetic core that has a small air gap.
The MOT primary coil normally is rated 5-10 amper, and the number of primary turns (120~180). This is enough to allows the core works bellow the iron saturation area when 120Vac is applied. So, the primary coil as is is suitable to work, without any modification.
Then we need to provide a air gap is adjustable (0.1 ~3.0mm) between the E and I cores. The result is a variable reluctance to the magnetic flow and a variable inductance. In this applicationthe the final effect is similar to a reostat in serie with the PT primary, allowing adjustment in the primary ac current.
The MOT modification consist in open the transformer magnetic core, remove the high voltage coil, close the core leaving a small air gap between the I and E core. In order to get good and practical core closing, the air gap may be filled up with a hard cardboard, plastic sheet, fiber material.
A tutorial explaining how to open the transformer the may be found in the site:
or read the thread "windings in a mot" , posted on march 31 2012.
(be more carefull to avoid any damage in the primary coil.)
I'd like see your solution how to provide a mechanic variation of the gap.
Regards
Newton
Re: Need 30 kilovolts!
Newton Brawn, Thu May 24 2012, 04:10AM
Hi All!
I have cut the transformer core welding by hand using a arc saw, hss, not a power grinder.
When I cut the the magnetic core in order to separate the I and E cores, I do not cut exact in the midle of the welding core .
The saw open a slot 1mm out of the welding center, in such way that the E core is not damaged. only the I core receive 1.5-2 mm deep scratch. When reasembling the E core with the I core invert the I core leaving the scratch out of the main magnetic flux.
If the cut is locate in the center of the welding, both E and I cores will be scratched, resulting in a reduction of area of magnetic flow (increasing the induction in that location), possible saturation
Regards
Newton
Newton Brawn, Thu May 24 2012, 04:10AM
Hi All!
I have cut the transformer core welding by hand using a arc saw, hss, not a power grinder.
When I cut the the magnetic core in order to separate the I and E cores, I do not cut exact in the midle of the welding core .
The saw open a slot 1mm out of the welding center, in such way that the E core is not damaged. only the I core receive 1.5-2 mm deep scratch. When reasembling the E core with the I core invert the I core leaving the scratch out of the main magnetic flux.
If the cut is locate in the center of the welding, both E and I cores will be scratched, resulting in a reduction of area of magnetic flow (increasing the induction in that location), possible saturation
Regards
Newton
Re: Need 30 kilovolts!
Newton Brawn, Thu May 24 2012, 04:15AM
The estimate reactance is about 25 ohm for a primary coil with 150 turns and a 1mm gap,
250 ohm for a primary coil with 150 turns and a 0.1mm gap.
The core cross section in question is 25 square centimeter, 0.0025m2.
Newton Brawn, Thu May 24 2012, 04:15AM
The estimate reactance is about 25 ohm for a primary coil with 150 turns and a 1mm gap,
250 ohm for a primary coil with 150 turns and a 0.1mm gap.
The core cross section in question is 25 square centimeter, 0.0025m2.
Re: Need 30 kilovolts!
Oneironaut, Fri Jun 22 2012, 09:15PM
[Update]
I have purchased this amazing 35kv beauty, and it works perfectly...
With a half wave rectifier, my HV probe reads 18kv, so now I need to source a bundle of HV diodes in order to make a full wave rectifier. This one has 17 diodes and is rated for 100kv....
Does anyone know of a good supplier for HV diodes? I found Amazing1, but there most be other suppliers. I would probably need 50 or more to make a full wave rectifier capable of taking the 35kv from my potential transformer.
One more question if I may...
Not having played around with potential transformers before, is it recommended to ballast them? When I had the pole pig, I used 4 stove elements in parallel as ballast and that worked well. A half dozen 500w halogen bulbs in parallel also worked and gave visual feedback when charging the capacitors (lights dimmed as charge increased).
I don't want to cook this 150 pound potential transformer - it wasn't cheap, and from what I can tell, it was a rare find!
Cheers!
Brad
Oneironaut, Fri Jun 22 2012, 09:15PM
[Update]
I have purchased this amazing 35kv beauty, and it works perfectly...
With a half wave rectifier, my HV probe reads 18kv, so now I need to source a bundle of HV diodes in order to make a full wave rectifier. This one has 17 diodes and is rated for 100kv....
Does anyone know of a good supplier for HV diodes? I found Amazing1, but there most be other suppliers. I would probably need 50 or more to make a full wave rectifier capable of taking the 35kv from my potential transformer.
One more question if I may...
Not having played around with potential transformers before, is it recommended to ballast them? When I had the pole pig, I used 4 stove elements in parallel as ballast and that worked well. A half dozen 500w halogen bulbs in parallel also worked and gave visual feedback when charging the capacitors (lights dimmed as charge increased).
I don't want to cook this 150 pound potential transformer - it wasn't cheap, and from what I can tell, it was a rare find!
Cheers!
Brad
Re: Need 30 kilovolts!
Thomas W, Fri Jun 22 2012, 10:22PM
wow, i really want one of those o.o, where did you find it?
ebay?
Thomas W, Fri Jun 22 2012, 10:22PM
wow, i really want one of those o.o, where did you find it?
ebay?
Re: Need 30 kilovolts!
Oneironaut, Fri Jun 22 2012, 10:28PM
Yep, EBay. I was thinking about hogging the other one for myself, but $500.00 is a bit much for a "spare"! Certainly worth the price though.
Brad
Oneironaut, Fri Jun 22 2012, 10:28PM
Yep, EBay. I was thinking about hogging the other one for myself, but $500.00 is a bit much for a "spare"! Certainly worth the price though.
Brad
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