Voltage multiplier and spark gap design

[rain2359]

Hi,

I am currently working on high voltage system, where I need to create an impluse at the primary side of a potential transformer. I am trying to charge my circuit to at least 10kV using a half wave series voltage mutliper consisting of capacitors and diodes, and discharging them through spark gap.

Currently I had successfully charged my voltage multiplier to 7kV, however, I can't seem to obtain a high voltage impulse. Whenever I obtain an impulse the magnitude of the impulse is not 7kV, instead it is only 100plus volt. Also, after running the experiment for a few more round, I will not be able to obtain impulse anymore, instead there is a lot of noise and sparks.

I am wondering if anyone could help me, I would like to know if the problem actually lies in the spark gap used or with the voltage multiplier? May I know that will the cross sectional area of the spark gap play a part in obtaining a sharp impulse? What type of the spark gap is suitable for this experiment?

Thank you very much.

 

[unplebeian]

I think the problem is with the multiplier. I don't know what your input voltage is, but if you simulate any multiplier circuit, you'll find that it takes several milli-seconds for the voltage to build up to the final voltage.

I am not entirely sure what the spark gap is doing here, but to get an impulse of 7KV is going to be difficuilt as you have to charge all the caps in the multiplier. How many stages of multiplication are you using?

 

[berkeman]

Which mulplier are you using?

http://en.wikipedia.org/wiki/Voltage_multiplier

http://blazelabs.com/e-exp15.asp

I agree that it sounds like your multiplier is developing a problem -- either the diodes or the caps are getting leaky. Are you sure you are not violating their reverse voltage specs?

 

[rain2359]

hi,
I am actually using 15 stages of multiplier, I am sure that I am not violating their reverse voltage spec, my input voltage is around 200V. May I know if there would be any problem if I were to continue to use this kind of multiplier? What are the other solutions that I can do? Thank you very much. :)

 

[unplebeian]

First of all 200V*15= 3KV only not 7KV.

Sometimes power supplies need to undergo a surge test upto 6KV. Perhaps you can look that up.

I'll post something when I find it.

 

[rain2359]

hmm, but we measure the voltage, its 7kV ... but not 3kV... hmm..

 

[unplebeian]

hmm, but we measure the voltage, its 7kV ... but not 3kV... hmm..

Have you tried considering a charge pump instead of a voltage multiplier?

 

[rain2359]

hmm.. can't actually use a charge pump, because the experiment is done in the lab and the lab does not have a charge pump, and can't buy it as well due to certain reason.

Had actually solved the problem, Thank everyone for your help. :)

 

[unplebeian]

hmm.. can't actually use a charge pump, because the experiment is done in the lab and the lab does not have a charge pump, and can't buy it as well due to certain reason.

Had actually solved the problem, Thank everyone for your help. :)

Charge pump was a bad idea. Sorry.

So, if it is solved can you post your circuit and a waveform? What probe/DMM are you using?

Thanks.

 

[rain2359]

still trying to work out the MATLAB to see the waveform, need some help in MATLAB before i am able to post the waveform, when i draw the circuit out, shall post it here. Thanks.:)