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Re: variac rewind





---------- Forwarded message ----------
Date: Sat, 11 Oct 1997 07:44:28 -0400 (EDT)
From: FutureT-at-aol-dot-com
To: tesla-at-pupman-dot-com
Subject: Re: variac rewind 

> One of my friends just got a hold of a reletively new looking but burnt 
> out 'Light dimmer' from a school. Several windings on one end were all 
> melted, and there were arc marks where the contact touched the winding. 
> This contact wasnt making good conection. Anyways, it is a 50A unit, 
> wound with #12 wire. I have two lbs of #13 enamel mag wire. Would the 
> #13 wire be OK so long as it isnt run for long periods at high current 
> levels? That is provided that the thing works at all. If I remember 
> correctly the name plate says 50A / 8kVA. The next coil that I might use 
> this variac on will be using probably three 12kV 60mA NST's. This 
> shouldnt be near the current limit of the variac anyways. But then again 
> with resonant charging I have blown a 15A breaker with a single 15kV 
> 60mA neon. (not neccesarily a good thing!)
 
> Any insight appreciated,
> Mad Coiler
  >>

MC,

Do you plan to replace only the burnt out windings, or all the windings?
It's a lot of work and difficult to rewind a variac.  Yes, the #13 wire
would be fine as far as current is concerned.  This is probably a step-
up type variac that can give 140V out.  You may be able to just cut
the wire where the burnt part begins, and don't use the burnt part.
Install some sort of "stop" that prevents the variac from turning far
enough to reach the burned windings.  Depending on how many
windings are burned, you may still be able to get 125V or 130V,
or whatever, out of the unit, this would be the easiest approach if
not too many windings are burned.  Variacs can handle considerably
more than their rated current for short periods.

John Freau