240 vac variac observation

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Yurtle Turtle by way of Terry Fritz <twftesla-at-qwest-dot-net>" <yurtle_t-at-yahoo-dot-com>

I'm probably stating the obvious to most of you guys,
but this is something I recently discovered, regarding
> 120 volt variacs.

In my neck of the woods, neutral = ground.

With a 120 volt variac, we are varying the output
potential relative to neutral. No problem. See below:

--------)
        )
        )<------  0 - 120 vac
        )
120 vac )
        )
        )
        )
--------)--------  common

-----------------  ground



In a 240 volt variac setup, we are varying the
potential relative to one phase, from 0 to 240 volts.
This results in an unsymmetric 0 - 240 volts relative
to neutral/ground. See below


--------)
        )
        )<------  0 - 240 vac
        )
240 vac )
        )
        )
        )
--------)--------  common

------------------ ground

For example, I have a 34 kV DC PSU which wants 208
vac. If I feed it from my big variac, one leg will be
at a higher potential relative to neutral/ground, than
the other.

Perhaps that's not a problem, but it might be for
some.

Adam

=====
Adam Minchey
yurtle_t-at-yahoo-dot-com
http://www.geocities-dot-com/yurtle_t/index.htm

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