[Boatanchors] Variac low?

[Fred Olsen]

StephenTetorka at cs.com wrote:
> Testing a low voltage power supply.
> However, the AC in was only 90 VAC out from the Variac at max control.
> Variac by itself 115 VAC at max control.

First, it's just possible that you might be overloading the variable 
autotransformer.  The idling current (you didn't say that the PS was 
loaded) of a very large supply might exceed the current rating of a very 
small 'Variac'.  Can you measure the current out of terminal 3 (usually)?

Given that you have the 'Variac' wired correctly it would seem that you 
have it wired for straight line rather than boost.  Fine.  But then the 
question arises of why you only get 115 at no load.  It's very uncommon 
to have that low a line (mains) voltage in the U.S. or Canada.  So where 
are you and what is your measured line voltage?  What make/model is the 
autotransformer and how is it wired?

If all else is correct might the 'Variac' be defective?  Perhaps a 
cracked core?

Good luck, be safe,
Fred
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