RE: variac amperage control?

To: tesla-at-pupman-dot-com
Subject: RE: variac amperage control?
From: "Alan Sharp" <AlanSharp-at-compuserve-dot-com> (by way of Terry Fritz <twftesla-at-uswest-dot-net>)
Date: Sun, 28 May 2000 09:34:54 -0600
Approved: twftesla-at-uswest-dot-net
Delivered-To: fixup-tesla-at-pupman-dot-com-at-fixme


>My experience has been 5 amps at about 75%
>winding usage, 10 amps at about 65%, 15 amps at about 60%, and over 25
>amps at between 45%-50%. After this, the current will go out of sight!!.
>GREAT care must be taken that you are so familiar with your variac that
>you will have it at full winding setting prior to powering up the unit.
>If by chance you are a the no winding setting, then you will have a dead
>short with no reactance, and in a microsecond no variac. With these
>cautions taken, the variac makes a very nice current limiter. <

Terry, all

I also use variac's for current limiting in this way, I'm using 110V 10A
units which are not much use for anything else in a land of 230v mains

But I put an a micro wave transformer primary in series with the variac,
the MOT secondary is shorted out - the current goes from about 5 to 15A

A bit of reactance in series will stop the variac saturating and the smoke
coming out.

Alan Sharp (UK)