Re: Transformer Question

To: tesla-at-pupman-dot-com
Subject: Re: Transformer Question
From: Jim Fosse <jim.fosse-at-bdt-dot-com>
Date: Wed, 18 Sep 1996 06:27:13 GMT

>> Subject: Transformer Question
>
>>From bturner-at-apc-dot-netTue Sep 17 22:15:12 1996
>Date: Tue, 17 Sep 1996 02:03:01 -0700
>From: open_minded <bturner-at-apc-dot-net>
>To: tesla-at-pupman-dot-com

>> I've been using two 4500VAC 400ma plate transformers pulled from copy
>> machines. These transformers (GE) have an extra winding that is
>> connected to a 660VAC 10uf capacitor.
>> 
>> Questions: What is the purpose of this capacitor? Power factor
>> correction? Current limiting? What effect would result by changing or
>> removing the capacitor?
>> 
>>    0---------) || (----------0
>>              ) || (
>>   LV In      ) || (
>>              ) || (
>>    0---------) || (
>>                || (
>>     |--------) || (   HV Out
>>     |        ) || (
>>    ---       ) || (
>>    --- 10uf  ) || (
>>     |        ) || (
>>     |--------) || (-----------0
>> 
>> Thanks...   ...Jeff Parisse
>
>
>Could be a PFC, or this actually could be a 'regulated' transformer
>ala the Sola 'constant-voltage' type line regulator. From what I
>remember, the large value cap and winding set up a 60-Hz resonant
>circuit. Line over-voltage is absorbed due to increased core saturation,
>and under-voltage is boosted due to resonance-rise in the tank circuit.
>
>- Brent
>

Brent,
	Could do either, 15 years ago I helped build some CV
transformers for Godbout electronics. They had shunts between the
primary winding, the secondary winding and the resonant winding.

Jeff,
	Schematic wise, it looks just like the winding of my Jefferson
Electric Neon that I unpotted several months ago. (15kV 60ma and 23uF)
Check the physical arrangement of the three coils. if the coil to the
PFC cap is wound ontop of the primary winding; it's there for power
factor correction. If it's a separate winding, isolated by magnetic
shunts; its for constant voltage regulation. Given the sensitivity of
a photocopier's contrast to voltage, I would expect it to be a
constant voltage winding and removing the cap will (increase?) the
output voltage by reducing core saturation.

I think bert is more versed in transformers theory here, I'll leave it
to him for a detailed explanation of ferroresonant transformer
operation;)

	jim