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[AMPS] Plate Transformer Ratings

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Subject: [AMPS] Plate Transformer Ratings
From: (Denis)
Date: Tue, 16 Nov 1999 22:52:54 -0600
Jim Smith wrote:
>     Hi all,
> I just purchased 2 old military transformers, still in their wooden crates
> for cheap. I figured I'd somehow be able to use them between all the
> projects I'm working on, but I do have a few questions.
> 1) Is there a simple way to convert between KVA ratings, CCS, and ICAS?
> 2) Are there special considerations required for transformers, or their
> cores when used in RF applications?
> 3) Does potting help with insulating the windings, or with heat dissipation,
> and thereby extend the life?
> 4) What is the significance of the secondary resistance?
>     The transformers I picked up are 110 volt primary, 3100 volt secondary,
> 1.7 KVA, weighing in at 85 lbs. each. I figured I could wire the primaries
> in series, and the secondaries in parallel if I wanted to feed them with 240
> volt, but then again that would be 170 lbs. just for the transformers.
>     I measured the secondary resistance at 214 ohms. It made no difference
> whether the primary was shorted or not. I don't know if it's of any use, but
> the primary resistance was 0.1 ohms.
>     Your comments are appreciated. Thanks in advance.
> Jim Smith, KQ6UV
> --
Jim, I just did some rough calculations and with the secondaries in
parallel. You would have a 'no load voltage' of 4350 volts. With 3KW
input into your amp that would be .70 amp. the power supply voltage
would droop to 3600 volts (abt 750 volt drop)

This is not very good regulation.  Good transformer have a secondary
resistance of 10 - 20 ohm and give 5 % regulation.

Denis VE6AQ

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