[AMPS] Re: QRO Pwr Sup Question

[Roy Koeppe]

George, pertaining to:

>I'm in the process of building a 3-500 amp from the dregs of
someone elses earlier project. I have the power supply built, but the
power transformer I used was designed for 220 VAC nominal rather than
the 240 (plus) that I have at my outlet.

The problem is that with a standard capacitor input filter my
no-load voltage is around 4300 VDC, which is a bit high for a pair of
3-500s.

Using a variac I have determined that 220 VAC gives me 4000
VDC no load. With the voltage dropping to 3400 under load.

Short of using a variac is there any practical way to lower
the primary voltage?<


If you happen to have a good quality 20-volt @ 20-amp transformer handy, you
can wire its secondary in series with the primary of the plate transformer,
phased for "bucking" the voltage by 20-volts, resulting in 220-volts
effective at the plate transformer primary.

73,  K6XK


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