Re: [TCML] Pushing a variac beyond rating

[Yurtle Turtle <yurtle_t@xxxxxxxxx>]

I push my two paralleled, motor driven, Superior Electric Powerstat 1256s to 
over 100 amps, which is nearly twice their rating. I have a high output fan 
blowing directly on them in my control panel. As long as you keep them cool, 
Powerstats can be overdriven quite a bit.



----- Original Message ----
From: Eric Goodchild <ericgoodchild@xxxxxxxxx>
To: Tesla Coil Mailing List <tesla@xxxxxxxxxx>
Sent: Fri, May 20, 2011 5:27:31 PM
Subject: Re: [TCML] Pushing a variac beyond rating

The maker of the variac has a big impact on how far you can push them. Cheap
china variacs can't even be run at there datasheet rating.

Powerstat and Staco are both good variacs and can be pushed past there
rating maybe maybe 25%. The limiting factors are the core and the wire size
on the variac. The core will be begin to saturate and make the variac
vibrate. This is not really damaging to the variac but can lower the output
voltage as it starts to saturate. The main thing to watch out for is the
contact between the brush and the wire, this is where the damage will happen
if you push to much current through the variac.

Test it slowly with small steps to determine how far you can push it. Try
this at your own risk as in any case it's not good to run parts past there
rated specs.

Eric Goodchild

On Fri, May 20, 2011 at 10:07 AM, Nicholas Hall <ngharo@xxxxxxxxx> wrote:

> Hello list,
>
> I have a Staco 5A variac that I've used with my 15/30 NST powered coil with
> no problems.  I've now upgraded to a 15/60 NST.
>
> I'm wondering how Variacs fail and if it's Ok to overload them for short
> periods.  I'm also wondering if keeping it in transformer oil would help.
>
> At this point I cannot afford a new variac (they're fairly expensive on
> Ebay) so if anyone has input it would be much appreciated.
>
> Nicholas Hall
> 262.706.1337
> ngharo@xxxxxxxxx
> _______________________________________________
> Tesla mailing list
> Tesla@xxxxxxxxxx
> http://www.pupman.com/mailman/listinfo/tesla
>
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