Voltage multiplier and spark gap design

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Discussion Overview

The discussion revolves around the design and troubleshooting of a high voltage system utilizing a half wave series voltage multiplier and spark gap for generating high voltage impulses. Participants explore issues related to voltage levels, circuit components, and potential solutions within an experimental context.

Discussion Character

  • Technical explanation
  • Debate/contested
  • Experimental/applied

Main Points Raised

  • One participant reports successfully charging a voltage multiplier to 7kV but only achieving a low voltage impulse of around 100 volts, raising questions about the spark gap and voltage multiplier performance.
  • Another participant suggests that the issue may lie with the voltage multiplier, noting that it typically takes time to build up voltage and questioning how many stages are being used.
  • Concerns are raised about the potential for leakage in diodes or capacitors within the multiplier, with a request for clarification on the specific multiplier being used.
  • A participant points out that with 15 stages and an input voltage of 200V, the expected output should only be around 3kV, not 7kV, prompting further discussion on the accuracy of the voltage measurements.
  • One participant proposes considering a charge pump as an alternative, but another participant indicates that this is not feasible due to lab constraints.
  • A later reply mentions that the original problem has been resolved, but requests for circuit details and waveform data remain open.

Areas of Agreement / Disagreement

Participants express differing views on the source of the problem, with some attributing it to the voltage multiplier and others questioning the measurement accuracy. The discussion remains unresolved regarding the exact cause of the low impulse voltage and the effectiveness of the current setup.

Contextual Notes

There are unresolved questions about the performance of the voltage multiplier and the spark gap, including the impact of component specifications and the accuracy of voltage measurements. The discussion also highlights limitations in available equipment for experimentation.

Who May Find This Useful

This discussion may be of interest to individuals working on high voltage systems, voltage multipliers, or those troubleshooting similar experimental setups in physics or engineering contexts.

rain2359
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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.
 
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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?
 
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?
 
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. :)
 
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.
 
hmm, but we measure the voltage, its 7kV ... but not 3kV... hmm..
 
rain2359 said:
hmm, but we measure the voltage, its 7kV ... but not 3kV... hmm..

Have you tried considering a charge pump instead of a voltage multiplier?
 
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. :)
 
rain2359 said:
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.
 
  • #10
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.:)
 

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