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Re: Saftey -Transformer type not the issue



Tesla List wrote:

> Thats one reason why some ppl store big HV caps with a shorting lead bolted
> across the bushes. I wonder whats the biggest cap you could charge from a
> TV fllyback transformer??

I used a multi stage multiplier (driven by a flyback type arrangement at
about 50-100 watts) to charge a 75 kV, 1.5 uF cap. That's several
kilojoules of stored energy, enough to do a LOT of damage. It took
several minutes to fully charge the cap, which was good because I didn't
have any sort of voltage limiting on the power supply to prevent
overcharging. I just waited until the voltage got as high as I dared,
then turned off the power supply. The last 10 kV takes quite a while.

Voltage multipliers are a good way to charge a cap because they put out
a lot of current at low voltage (when the cap is just starting to
charge) and then the current tapers off as the voltage comes up. HV
diodes and small caps are a whole lot cheaper than a HV transformer for
100 kV.

Joachim Kronjaeger has a bunch of multiplier arrangments on his web page
made by stacking standard TV triplers.

Voltage multipliers run at high switching frequencies (10's of kHz) are
also nice as general purpose HV supplies because they have low stored
energy, so the inevitable flashover doesn't do too much damage.  Of
course, this advantage goes away if you are charging big caps up, and an
internal flashover in the supply will destroy it if you have that big
energy storage outside.