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Re: VARIAC's -> parallel??
> My friend was talking to an engineer at a variac company the
other day.
> He warned against putting variacs in parallel. Apparently, if the output
> voltage of each variac is a little different, there will be heavy current
> flow between the outputs due to the unbalanced voltage. He had some
> special choke or something for $100 that would fix this problem and allow
> them to be put it parallel. Anybody ever heard this before??
This can be a problem sometimes, if the variacs are more than a few volts
different at any point in their range there can be very large loop current
which can
damage them. The way I get round this is simply to put all the variacs on
the same
shaft, and then spend a long time with a DMM across the outputs of the variacs
measuring the voltage difference. Then I mess around with rotating the
variac on the
shaft until all the variacs are within 1 volt of each other at all points
on their
range. If there is a variac which, due to nonlinear output, can't be
balanced, it
has to be left out of the stack.
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