Re: From Member: using Digital Equipment Corp Transformers

Doug Pollard wrote:

> dcassyc1 wrote:
>
>> Hi All,
>> I have a DEC power transformers which uses an oil filled capacitor on
>> one of the windings, I suppose to provide Power Factor correction. The
>> capacitor is missing and I don't know what value it should be.
>> Is there a method I can use to determine the capacitor value?
>> Is it possible to use this transformer without the capacitor?
>> cheers,
>> Denis
>>
>>
>>
> I'm no expert on this stuff but I believe the only reason to use a
> capcitor is to supply a jolt of electricity to something like a motor
> that needs to start under a load.
>

No, the "oil filled" capacitor he is talking about is clearly associated
with a ferroresonant regulating transformer.
We haven't seen stuff like this since the late 1960's, as they are
expensive to make, heavy, and very inefficient, as part of the
regulation scheme requires running a section of the iron at saturation,
and due to hysteresis loss, the core runs hot.

This is totally different from the usual DC power supply capacitors you
are thinking of, which are connected after the rectifier, and would be
electrolytic type instead of oil-paper type. The ferroresonant cap is
connected directly to a special winding on the transformer.

Jon