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Re: MOT Voltage Doubler
Tesla List wrote:
>
> Original Poster: "Gregory R. Hunter" <ghunter-at-enterprise-dot-net>
>
> Dear List,
>
> I'm amazed at the interest this simple posting has generated. As long as
> I'm stirring the pot, I might as well throw in my own 2 pence worth. For
> one thing, I'm puzzled by the huge disparity in MOT outputs. I've measured
> a few US-type MOTs from Litton, Sharp, JC Penny, and Hitachi ovens with a
> Fluke DMM (and the optional 1:1000 HV probe!), and they all put out exactly
> what they advertised. The smallest one put out 1890VAC-at-285ma, and the
> largest 2250VAC-at-385ma. I measured the output current just like an NST, by
> shorting out the secondary with a DMM set on AC AMPS. The shunts worked
> perfectly--no smoke, no popped breakers, no damage to meter.
>
> The point I was trying to make about the voltage doubler circuit is that if
> it only raises the voltage to 2.8 x RMS, then there's little point in
> including it in a TC power supply. Consider the case of two identical
> 2200VAC MOTs with their cores shorted together and grounded, their
> secondaries in series, and primaries reverse-phased. The two MOTs will
> develop 4400VAC as measured across the two HV output terminals. 4400VAC x
> 2.8 = 12320V peak-to-peak. Now, if we include tho two voltage doublers, we
> get roughly 12320VDC pulsed (2200 x 2.8) + (2200 x 2.8). If a TC is being
> fired by 12320V, does it matter that much if it's AC or pulsed DC?
But, oops, the AC case is 12kV peak to peak, but the voltage across the
output is only half that at a maximum, or 6 kV. The doubler
configuration allows you to work the maximum positive voltage against
the maximum negative, whereas the AC configuration gets only to the peak
voltage (1.4 *Erms), albeit with opposite sign each time.