Hi-Pot tester.

Discussion in 'The Projects Forum' started by PackratKing, Aug 2, 2008.

  1. PackratKing

    Thread Starter Well-Known Member

    Jul 13, 2008
    Building a hi-pot rig, first design based on the HV transformer out of a defunct microwave.

    A friend told me I would be safer to use a florescent ballast for the high voltage source, since the available current would be more in line with the application.

    Maybe even rectify it, to have both ac/dc available.

    Any thoughts, Guys & gals ??
  2. SgtWookie


    Jul 17, 2007
    Your friend is a buddy indeed :)

    Microwave transformers can put out around a KW. You just want to know if there's a voltage leak somewhere, not fry the thing into oblivion. Well, then again maybe you do, I don't know.

    You could also experiment with an automotive ignition coil. You could regulate the voltage somewhat by using a spark gap. A generally accepted formula for an air gap is three million volts per meter, or 76,200V/inch, or 76.2v per mil (0.001 inch). So, a gap of about 0.0394" would give you just about 3kv. Set an ordinary automotive sparkplug to that gap, and you have a HV clamp. Of course, that's a bit of a crude way to do it, because once the air is ionized, the resistance of the air will be much less - thus the voltage across the gap will drop until the ionization ceases, and the process repeats.

    Check out Ronald's "Flyback Converters for Dummies" page:
    It's not really "for dummies", Ronald just has a great sense of humor.

    About 1/3 of the way down the page, he shows a flyback HV supply for nixies. No reason why you couldn't adapt that design to provide much higher voltages.

    The big thing is getting the voltage up there, while making sure you won't have more than a few mA current. If you're going to use HV caps, make sure they're very small. Otherwise, that stored-up energy will blast a big hole in whatever it eventually finds a conduction path through.

    HV DC isn't as dangerous as HV AC. AC will trigger ventricular fibrillation at much lower current levels than DC will.
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