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Good Pig


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From:  Eric Davidson [SMTP:edavidson-at-icva.gov]
Sent:  Wednesday, February 04, 1998 2:39 PM
To:  Tesla List
Subject:  Re: Good Pig

Greg:

Your resistance readings seem appropriate. The primary resistance will
decrease slightly with kVA rating at a constant primary voltage reading.
In other words, the primary resistance of a 5 kVA 13,800/240/120 tranny
will be slightly LARGER than the primary resistance of a 50 kVA
transformer of the same voltage rating.  I don't know how big a unit you
have. Don't be scared to apply voltage to the secondary (LV side). This
is really the best way to test the insulation integrity of the unit. Be
sure that the transformer is fill with oil. You can start by putting
120v across the 240v bushings and see what happens. If you don't trip a
breaker or see any sparks, go with 240v. Be sure the tank is solidly
grounded, especially if it is on a wooden skid or if it has a single
bushing primary. Smaller trannies dont have much in the way of core
losses and wont draw enough power to be noticeable. You may be able to
hear it hum. Stay well clear of the primary terminals. Pole pigs are
much different than NSTs. Even a 5 kVA unit can supply a few amps at
13,800 volts. This current will burn at the very least if you are lucky?
enough to survive. I know you know this already, but be careful. Hope
this helps.

Eric
<edavidson-at-icva.gov>
	
Tesla List wrote:
> 
> ----------
> From:  Gregory R. Hunter [SMTP:ghunter-at-mail.enterprise-dot-net]
> Sent:  Tuesday, February 03, 1998 4:03 PM
> To:  Tesla List
> Subject:  Good Pig
> 
> Coiler Types,
> 
> I've been tinkering with my new pig, trying to ascertain if it's
> serviceable or not.  I'm too chicken to apply mains power to it--I
> don't have anything to ballast it with.  I ohmed the 11KV winding,
> and the needle (honest, a moving needle) slowly settled down on
> about 350 ohms.  The 240V winding was practically a dead short.  I
> have no idea what the resistance of pig windings should be.  Do my
> readings sound right?
> 
> I was desperate to test it somehow, so I tried my 6 amp car battery
> charger on it.  I made a spark gap of about .25" with some stiff
> wire.  I clipped one charger lead to one 240V terminal.  I tapped
> the other charger clip against the other 240V terminal, and
> was rewarded with a sharp "SNAP" across the spark gap.  I think it
> works!  Not bad, considering the price tag  (it was FREE).
> 
> Greg
> 
> Tickling the Pig's Tail in East Anglia, UK