According to Ted Samuels :

[ ... ]

Got quite a surprise today. Tried running one of my 60 volt DC motors (I
thought they
were 90 volt motors) with a variac and my setup tripped the breaker in my power bar.
Checked and rechecked the circuits from the variac through the bridge and motor and
everything seemed logical. tried it again and again it tripped (not very smart
really). Then I happened to notice in small print on the very front of the variac
"360 cycles per minute" 6 HZ

I've never seen one of those, and I would think that one for
such a low frequency would have enough iron so it would have no troubles
with 60 Hz. Are you sure that wasn't "360 cycles per second"? That
would be close to the 400 Hz ones which I have used -- and *those* just
plain won't work with 60 Hz at normal voltage. :-)

also -- was it a genuine Variac (made by General Radio), or
another brand of variable autotransformer? The 400 Hz ones above were
genuine Variacs.

Enjoy,
DoN.
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