Re: variac question?
- From: Jeff Wisnia <jwisnia@xxxxxxxxxxxxxx>
- Date: Wed, 10 Oct 2007 11:48:58 -0400
Grant Erwin wrote:
I have a 20 amp variac. Yesterday I tried plugging it into a 20A circuit with its output voltage set to 30% of input voltage, and it (consistently) popped
the breaker. When I set it to 100% of output voltage, however, it didn't pop
the breaker. Obviously the magnetizing current is higher with the variac turned
down. The question is why? What's going on here?
I believe the variac and my electrical circuits are both in good working condition, in other words I don't believe this is faulty behavior.
Grant Erwin
Kirkland, Washington
Just a WAG, but maybe the sliding contact has worn "flat" and is touching too many turns of wire, creating a multiturn shorted winding when set at the 30% position, thus causing the problem.
You didn't say whether your variac is a 0-100% kind or the kind which can output more than 100% of the input voltage.
If it's the 100% kind, then maybe when it's set to 100% the contact arm is no longer resting on the winding but is on a broader piece of metal connected to the hot input.
More details please. If you plug it in at 100% and then lower it to 30% do things stay OK?
Jeff
--
Jeffry Wisnia
(W1BSV + Brass Rat '57 EE)
The speed of light is 1.8*10^12 furlongs per fortnight.
.
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