Re: Ballast

• To: tesla-at-pupman-dot-com
• Subject: Re: Ballast
• From: "Malcolm Watts" <MALCOLM-at-directorate.wnp.ac.nz> (by way of Terry Fritz <terryf-at-verinet-dot-com>)
• Date: Wed, 04 Nov 1998 19:57:24 -0700
• Approved: terryf-at-verinet-dot-com

Hi Viv,

> Original Poster: "Vivian Watts" <V.C.Watts-at-btinternet-dot-com> 
> 
> Hi all,
>     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?

It reduces the unshorted winding to a fraction of its original 
inductance but not to zero. You cannot do that with any transformer 
let alone a welder because k never gets to 1 (although pretty darn 
close in pigs and the like). The welder is a bit like a NST with an 
adjustable shunt path and this shunt path takes over from the 
secondary leg if the secondary is shorted.

Malcolm

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