RE: Overrating a Variac

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

Original poster: "Basura, Brian by way of Terry Fritz <twftesla-at-qwest-dot-net>" <brian.basura-at-unistudios-dot-com>

The Superior Powerstat catalog contains a graph showing the
overload capacity for all Powerstat models. 

Terry had it on his site somewhere but I can't find it at the moment (Terry
- Help)

http://hot-streamer-dot-com/TeslaCoils/Misc/VarBack.jpg

Figure F

All variable transformers have a large thermal mass, and are wound with
wire that can handle many times the nameplate rating. Rather severe
overloads can be tolerated, as long as a cool-down interval is provided
between overload cycles.  Make sure that brushes, commutators and slip
rings are clean and bright to avoid localized overheating due to high
resistance at the brush contact points.

Essentially, the (interpolated) data-points of interest to coilers are:

On time        Overload  Cool-down
30 s    	   400%      8 minutes
1 min          350%      12 minutes
2 min          300%      17 minutes
5 min          250%      30 minutes
10 min         225%      40 minutes

Regards,
Brian B.


-----Original Message-----
From: Tesla list [mailto:tesla-at-pupman-dot-com]
Sent: Monday, October 29, 2001 3:52 PM
To: tesla-at-pupman-dot-com
Subject: Overrating a Variac

Original poster: "Jason by way of Terry Fritz <twftesla-at-qwest-dot-net>"
<jasonp-at-btinternet-dot-com>

Hi all,

I have a 10A variac and I have a 20A variac bruch that I picked up off a
friend. Provided that it physically fits in the old variac, does this mean
that I will be able to overrate the variac by more than usual??

thanks
Jason