Re: Ballast

To: tesla-at-pupman-dot-com
Subject: Re: Ballast
From: "Bill the arcstarter" <arcstarter-at-hotmail-dot-com> (by way of Terry Fritz <terryf-at-verinet-dot-com>)
Date: Wed, 04 Nov 1998 19:44:55 -0700
Approved: terryf-at-verinet-dot-com

Vivian Watts wrote:
>    I have just acquired an Uninteruptable Power Supply (UPS) from 
>a scrap yard.  The model is an Upsonic 200 A series if that means 
>anything to anyone.  Its rated at 2KW for 10 minutes.  Anyway it has 
>a large transformer in it which I guess is a step up of 1:2.  I'm 
hoping 
>to get a pole pig soon and was considering using this a ballast.  The 
>inductance comes out at 0.125H on the primary and 0.25H on the 
>secondary.  I've heard of people shorting out the secondary on 
>welders but surely this then presents zero inductive impedance then. 
> Any thoughts?

I'm told most folk use about 2-6 ohms of resistance and about 5-30 mH of 
inductance to ballast their pigs.  The transformer you mention sounds 
like it has way too much inductance!

Be sure this transformer is *really* a traditional 60/50Hz iron cored 
laminated transformer, and not some sort of ferrite core (as part of a 
switcher supply found in some of the large UPS units).  I guarantee you 
can't use that transformer for ballasting if it is ferrite!

You might try shorting the secondary of that transformer and 
re-measuring the inductance of the primary.  That may give you a value 
closer to what you need.

Welders are designed to be current limited (usually due to an air gap 
/flux leakage in the core etc)  Shorting the output of a welder won't 
cause a large primary current to be drawn by it's very design!

Later!
-Bill

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