>
>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?
>>
? no
>> 3) Does potting help with insulating the windings, or with heat dissipation,
>> and thereby extend the life?
>>
? All of the above.
>> 4) What is the significance of the secondary resistance?
>>
? It relates to the current capability of the transformer.
>> 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.
? The primary is shorted only to protect the ohm meter from reverse EMF.
>>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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>
- Rich..., 805.386.3734, www.vcnet.com/measures.
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