Thread: BIG variacs
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Pete C. Pete C. is offline
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Default BIG variacs


Ecnerwal wrote:

In article ,
Karl Townsend wrote:

Xmas came early this year, a couple a great big variacs showed up in
the mail today. Thank you Santa Pete.

These monsters have a common shaft so two can be turned in unison,
nice feature as i need to hook these up 220. Just want to verify the
hookup: The hot lead on each variac to each leg of the 220, the wiper
for each variac to the load, tie the nuetral on each variac together
and to nothing else (not ground that is). Correct?

Karl


Sorta depends what you are trying to do. You can wire a variac (single)
straight across 220 - usually there's even a second face to the dial for
that which reads 0-280V rather than 0-140 (most of the variacs I've met
have taps so they can run 120/240 in up to 140/280 out if desired, or be
wired such that they are limited to line voltage only, depending what
you want.)

If you want to make variable US-Spec 220V power with both sides varying
the same amount, you want 120-0-120 just like the service, which means
the "centers" (0 side of the winding) is tied to neutral, which is tied
to ground at the service entrance.

If you just need variable 220V power and the item is not using neutral,
and is properly insulated to use regular 220VAC, you can just use a
single variac and "0" will be both sides 120VAC away from ground
together, no volts between - just don't confuse "0" with "off" and get
bit.


I don't believe you can use a 120V rated lighting Variac on 240V singly.
Remember these are sections from a three phase lighting control, they do
0-120V, no over range like some test bench variacs and they were used
with three sections, one for each 120V to neutral phase of the 208/102
Wye service.