I am currently trying to build a power supply for multiple kV. According to Wikipedia an arc has about the same resistance as Metal. I am building my power supply with following parts:

  1. frequency modulator to 42kHz rated for 250W
  2. flyback transformer
  3. (voltage multipliers for DC and increased voltage)

So if i were to create an arc between the outputs, the circuit would have to supply tremendous amounts of power and melt unless i connect a ballast, right? I found this video on youtube: at 0:58 you can see how they only have a halogen transformer connected to a flyback transformer and are creating continuous arcs.

So how are they doing it and do i need a ballast for my setup?

  • \$\begingroup\$ How else is it going to reach the surface if it starts taking on water? \$\endgroup\$ – CogitoErgoCogitoSum May 5 '17 at 17:22

You can use a ballast or you can implement an active current limit protection into the switching circuit. This is how it's usually done but, you still need to take care of transients not blowing diodes if you have (say) a cockcroft walton multiplier stage on the output.

I once designed a 50 kV 200 watt supply for an X-ray machine and I used current limiting at the low voltage end. You might consider not using a flyback topology too because they start to sometimes get a little flakey above 100 watts (generalism alert). I used a fixed frequency forward converter producing about 5 kVp-p then onto the cockcroft walton multiplier (bathed in oil) for the final conversion to 50 kV.

The fixed frequency forward converter was fed from a variable output level buck converter in order to set output voltage levels appropriately. The current limit was in the forward converter.

  • \$\begingroup\$ thanks, though i still don't understand why the contraption in the video didn't melt. I heard about people simply using resistors as current limiters. Would this work and wouldn't it affect the output voltage? \$\endgroup\$ – this.foo May 5 '17 at 20:08
  • \$\begingroup\$ Sure resistors affect the output voltage - as you take more current the output voltage drops linearly. A current limit circuit doesn't suffer from this until the current limit is reached. I don't watch youtube videos because I can't trust links. \$\endgroup\$ – Andy aka May 5 '17 at 20:20

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