[AMRadio] Plate transformer identification

Mel Farrer farrerfolks at yahoo.com
Sun Jan 26 19:23:12 EST 2014

This an interesting problem.  One that, somewhere in the past I ran across this non-distructive test.  If you put a AC current meter across the secondary in a DEAD SHORT connection, and bring the primary AC up with a variac from ZERO volts, you will reach a point where the AC current stops rising.  This is the transformer saturation point and the maximum amount of current the transformer can deliver.  It doesn't tell you the ratio of the transformer or the ratings of them, but it is a starting point.

Good luck,

Mel, K6KBE

On Sunday, January 26, 2014 3:51 PM, John King <k5pgw at yahoo.com> wrote:
I have an open frame plate transformer that weighs 90 pounds. It bears the numbers IPC-XXX- 000003-B.
The transformer is open frame construction but the windings are sealed. It has an input terminal strip with leads that go to  7 taps for the primary. It measures approximately 0.7 ohm across the entire primary windings. The taps are apparently 0.1 ohm apart, so the transformer probably was manufactured for a purpose that required an adjustable voltage on the secondary.

The secondary terminals are marked 8 and 9 and the total secondary winding resistance is 12 ohms. The secondary does NOT have a center tap.

This is all I know about this beautiful "like new" clean transformer. I acquired it from an estate and it was obviously a project in progress when the Amateur died.  There are four Varco 80 diodes wired in a bridge across the secondary. Each rectifier block is rated at 8K volts at 1 AMP each. The project appears to have been a 4CX1500 B amplifier under construction.

Since I don't know the voltage and current ratings of the transformer, I will either hook a Variac to the primary or hook a low voltage transformer to the primary and determine the ratio of vac in to vac out of the secondary. That will tell me the likely secondary voltage with 115 vac into taps 1 and 2 but will not give me a hint about  the current delivery capability of the transformer. So, my question is anyone whether might recognize the identity of this transformer? Does anyone have any idea, given the resistance of the secondary, what the power delivery of the transformer might be? In connection with the thoughts about the characteristics of the wire and windings in the transformer does the weight being 90 pounds  have any bearing on your thoughts about the power handling characteristics of this transformer? 

If you feel that it would be best, for the list, please feel free to share your information directly to me. If you don't have experience with high voltage  and high voltage supplies, please don't clog up the reflectors to reiterate the obvious. Any and all information based on actual knowledge and experience will be greatly appreciated. Thanks and 73, John, K5PGW 
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