Re: Variac ratings

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "davep by way of Terry Fritz <twftesla-at-qwest-dot-net>" <davep-at-quik-dot-com>

   ....


>I was planning on using:

>120V, 20A variac for mains power (15kV/60mA maximum)
>120V, 8.5A variac for SRSG Phase Controller

>My question, is can you push a variac for short periods

>of time.  In example, can i push my 8.5A variac to say

>12A for short periods of time.
         How long is 'short'?

         Most transformer type devices will tolerate
         some degree of overload for periods of minutes,
         plural, up to 5 or 10.

         Extreme overload can lead to magnetic saturation
         problems.  Also, Variac can get into trouble if
         run over spec at small/low settings, as much current
         (and power) is being drawn from a small portion of
         the winding.

         If 'pushing', suggest assuring Really Good
         ventilation.  This won't help with magnetic
         saturation, it will help with cooling, which is the
         limit on many other things.


>If so, I could just use two (2) 120V, 8.5A variacs on the

>front instead of that monster 20A variac which is rather

>large.
         I'd guess it would work, tho conservative design is

         generally better.

         Comments?

-- 
         best
         dwp

...the net of a million lies...
         Vernor Vinge
There are Many Web Sites which Say Many Things.
         -me