# [Amps] UTC BS-497 plate transformer

Jim Thomson jim.thom at telus.net
Sun Mar 5 14:04:36 EST 2017

```Date: Sun, 5 Mar 2017 05:43:12 +0000
From: "Fuqua, Bill L" <wlfuqu00 at uky.edu>
To: "amps at contesting.com" <amps at contesting.com>
Subject: [Amps] UTC BS-497 plate transformer

I have found a nice plate transformer, a UTC BS-497.

I can't find any specs on it. All that I can tell is that it has 2 primary windings for 110 and 120 volts and has  a tapped secondary, with CT and two terminals for 3000V and 3500V.

I can't find it in any of the catalogs I have.

Would like to know the DC current and power capacities of the transformer.

TNX es 73

Bill wa4lav

##  Is it  EI plate  construction.....or tape wound ?    How heavy is it.  Put a temp short across the 120 vac prim...and measure the DC resistance from CT  to  EITHER 3 kv terminal.
Then again   from CT to EITHER 3.5 kv terminal.     Then put a temp short across the 2 x 3.5 kv terminals..... then measure the DC resistance across the 110 winding...then again for the 120 vac winding..... both are probably referenced to
a  0  terminal.    IE:  0-110    and  0-120.     Measure between  0 +  110....then  again between  0+ 120.

##  Knowing the weight and  the dc resistance on the sec   will tell us..usually, every thing we need to know.    What you have is called a 7000 v, CT xfmr.    Turns ratio is  7000 / 120 =  58.33         Turns ratio is also  7000 / 110 =  63.63
With a turns ratio that high, the max dc current you can draw will be limited...but that depends on weight.   In contrast, my drake L4B  xfmr has a 900 vac sec and a 240 pri.     900 / 240 =   3.75  for the turns ratio.

##  Ancient hammond plate xfmrs of the 80 lb variety, would have pri taps at  0-105-110-115-120    Sec is typ 3450-0-3450   They were designed for choke input..and would deliver 3 kv under a CCS load of 500 ma.   750 ma with a 50% duty cycle = ICAS rating. They were rated at 2.2 kva CCS.

Jim  VE7RF

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