Re: Run a 120v variac on 240???

> Okay, on a similar, but opposite, note, how many amps, at 120V 60Hz,
> could a 220V 10A 50Hz variac handle? At a 2200VA rating, I would think at
> least 20A, but the the 50Hz rating will allow it to carry even more
> current at 60Hz, won't it?

The current rating is due to the IR drop in the wire, and will be the same,
regardless of voltage... So your 10A 50Hz variac will carry 10A at 60 Hz.  

The different frequency means that the 50Hz unit has a bigger core, which
means that it can take more volts/turn at 60 Hz (oddly, 20% more...), so
you could run a 100V 50 Hz unit at 120V 60 Hz...

The VA rating isn't as relevant for a variac... What you really have is a
volts rating (determined by the number of turns, the frequency, and the
core) and a amps rating (determined by heating of the wire).  Multiply max
volts by max amps and you get the VA rating.....

They're rated in VA instead of Watts because the losses are due to current,
independent of the power factor.  You hook a 1000 VA load with 0 power
factor (i.e. a big capacitor or inductor) and the variac gets just as hot
as if you hooked up a 1000W load (a big resistor)...  The RMS current is
the same in both cases, just the phase relative to the voltage changes.

> I have two, and might like to gang them to control a potential
> transformer or small pig in the future...
> This is an interesting variac...
> nameplate reads:
> Variatore Di Tensione
> (lic. General Radio Co.)
> Ing. S. & Dr. Guido Belotti
> Piazzo Trento 8- Milano
> I don't speak Italian, but I can guess what most of that means.

Clearly, you need to call up Alitalia and get a plane reservation to Milan
so you can investigate the history of your Italian Variac fully... Science
demands no less...