[Prev][Next][Index][Thread]

Large Variac Help


From: 	Bill Noble[SMTP:william_b_noble-at-email.msn-dot-com]
Reply To: 	Bill Noble
Sent: 	Sunday, January 11, 1998 12:30 AM
To: 	Tesla List
Subject: 	Re: Large Variac Help

I expect what you are measuring is fine - you are making a DC measurement,
but the variac is an AC device, and it's inductance limits the current flow.
If you want to be sure, put a 100 watt light bulb in series with it, and
plug it in and see what happens - put another light bulb on the variac so
you can (if the variac is working) vary the brightness of the second bulb.
If it works, you will know it's ok.
-----Original Message-----
From: Tesla List <tesla-at-pupman-dot-com>
To: 'Tesla List' <tesla-at-pupman-dot-com>
Date: Saturday, January 10, 1998 10:10 PM
Subject: Large Variac Help


>
>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
>
>
>
>