Large Variac Help

• To: "'Tesla List'" <tesla-at-pupman-dot-com>
• Subject: Large Variac Help
• From: Tesla List <tesla-at-stic-dot-net>
• Date: Sat, 10 Jan 1998 23:45:01 -0600
• Approved: tesla-at-stic-dot-net

From: 	Barton B. Anderson[SMTP:mopar-at-mn.uswest-dot-net]
Sent: 	Saturday, January 10, 1998 2:09 PM
To: 	Tesla List
Subject: 	Large Variac Help

I have a Variac I think is shorted. Here's the specs:
GE, Input 120/240V, 50/60Hz, 1PH, Output 0 - 240/280V,
30 Amps.

There's 7 taps and #3 is the variable output tap. My
problem:    I'm measuring winding dc resistance and
the Fluke reading 0.6 ohms at pins 1 and 4 (full
winding). Measuring all the other taps from tap #1
common as well as all other combinations is below 0.6
ohms. I don't have a lot of experience with variacs,
but something tells me this isn't right. I first
expected a wire short, but from all the other tap to
tap measurements, there would have to be multiple
shorts between each. This does not seem probable. It's
got me a bit confused. The winding core is epoxied to
a metal base, but there's no short between base to
windings. There's no burnt smell and no visible burnt
wiring. I assumed the amount of wire wound would have
to read larger than 0.6 ohm dc resistance? Has anyone
with a large variac measured dc resistance with the
same results? I don't feel comfortable plugging this
in yet. Do I have a reason for concern?

Any comments greatly appreciated,
Bart

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