On Wed, 7 May 2003 11:56:54 -0400 "Jeffrey Madore" <K1LE@ARRL.NET>
writes:
> I have a transformer question that someone might be able to shed some
> light on.
>
> One of the components in these power supplies is a power transformer
> with a 240v primary. On the schematic diagram it shows another
> winding on the primary side which is connected to an 8uf 660v oil
> filled cap. The secondary is connected to a block bridge rectifier
> with capacitor filter. The transformer core measures about 5"x6"x2".
> I understand basic transformer theory and have a handle on primary
> field, secondary field, and the action of each on both windings.
> Now, entering the picture, is another winding with a capacitive
> load. Is the field of this winding somehow affecting primary XL?
> Could it be that the higher Epri resulting in higher Ic, causes a
> field that opposes the primary field to some degree, thus lowering
> XLpri? I'm getting lost... Is this a method of improved
> regulation? Has anyone experience with a transformer such as this?
<snip>
Hi Jeff,
Sounds like you have a constant voltage transformer. A modern
relic.
The extra winding with the capacitor is a compensating winding which
is operated unsaturated. It is magnetically coupled to the main winding
which is run saturated. The core is cut specifically for this
arrangement and probably incorporates an air gap between the main and
compensating portions of the core.
This scheme requires some value of minimum load to maintain
regulation. Also it is not very efficient -- somewhere in the vicinity
of 50%, so the unit will probably run quite warm. It will also likely
have a considerable stray magnetic field -- just the thing to cause
trouble with adjacent low level circuitry!
Sola Electric used to make a lot of these... 50 years ago. You may
be able to find some info for them on the web.
For a technical reference see: Nonlinear Magnetic Control Devices by
William A. Geiger, McGraw Hill 1964, pp 69-72.
73 & Good morning,
Marv WC6W
>
> Thanks you for any information, theories, practical experience, etc
>
> 73 de
> Jeff - K1LE - CT ><>............ar
>
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