[AMRadio] Ferroresonant transformer revisited

Jim Candela jcandela at prodigy.net
Sun May 7 13:13:55 EDT 2006


   If the idle power draw is about 20% of the rating,
then I figure you can mull that around and conclude
how much that is, and how hot that might get. These
Ferros's are not noted for efficiency, but if they are
loaded near capacity, 80% is doable. It's kind of like
a car at 55 mph that might get 25 mpg, and when
sitting at a long Texas red light the motor still gets
hot, and yet the mpg is zero.

Did I answer the question? :-)


--- W5OMR/Geoff <w5omr at satx.rr.com> wrote:

> Jim Candela wrote:
> >Rick,
> >
> >    The ferroresonant transformer is not really
> >resonant at all since the winding that feeds the
> >capacitor is wrapped around a portion of the core
> >that is a saturable reactor. Resonance and
> saturable
> >reactors don't really go together, but in this case
> we
> >do have circulating energy in a ferroresonant
> >transformer which consumes about 20% of the VA
> rating
> >of the device. So for a 1 KVA ferroresonant
> >transformer the power draw when unloaded may be
> about
> >200 watts, and this is pretty much a constant.
> >Therefore with a 1 KVA load, the power input would
> be
> >1.2 kva. Every line cycle runs the core into
> >saturation, and this creates eddie core losses,
> heat,
> >buzz, and a quasi square wave output. The output is
> >not a sine wave unless yours has a harmonic filter.
> >Therefore a true RMS meter is needed to accurately
> >measure the AC voltage.
> >
> >These are really neat devices using very old
> >technology.
> >
> which covers everything *except* what Rick asked,
> Jim (grinz).
> How hot is the darn thing -supposed- to get?  I,
> too, wouldn't think 
> that it's hot enough just sitting there, with no
> load, that you couldn't 
> put your hand on it..
> --
> -Geoff/W5OMR
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