Re: current limiting on pole transformers

From: 	Esondrmn-at-aol-dot-com[SMTP:Esondrmn-at-aol-dot-com]
Sent: 	Thursday, July 24, 1997 12:22 PM
To: 	tesla-at-pupman-dot-com
Subject: 	Re: current limiting on pole transformers

In a message dated 97-07-23 22:34:35 EDT, you write:

 I have recently purchased a 14.4kv, 10kva single phase pole transformer for
 a good price. I understand current-limiting due to working with high power
 radar systems for a defense contractor, but my question is why under-
 saturate the 240v side? the transformer I bought is rated  at 42 amps max
 on the 240v side if used as an input. According to the specs from the
 manufacturer this is the max current it will draw when fully saterated. If
 I hook this one up to a 60 amp service and somewhere get a 50 amp or more
 240v variac (does anyone have one for sale or a source?) I should not have
 a problem I would think. I'm trying to get away from welders, convection
 ovens, and I really don't want to use neon sign transformers. Any help is
 Rodney >>


A typical pole transformer will NOT limit its current draw.  If the secondary
is shorted or loaded heavily, the primary (240 volt input side) will draw all
the current it can get.  If the primary breakers or fuses can take it, the
lights in the house will get dim.  If you calculate the primary current with
the secondary fully loaded to 10kva, you do get 42 amps - but believe me, you
will be able to draw two or three times this much current with no current
limiting.  You could run that transformer at 20kva (82 amps in) for several
minutes without even warming it up much.

Ed Sonderman