Re: Transformers

[William Beaty <billb@ESKIMO.COM>]

On Tue, 5 Dec 2000, Bernard G. Cleyet & Nancy Ann Seese wrote:

> One can add some history by telling the story about Westinghouse and Tesla and
> his rotating magnetic fields.

I recently saw a patent for a rotating-field transformer.  It was a torus,
but with an extra coil wrapped around the perimeter and driven with a
90deg phase current.  The goal was to save energy by keeping the b-field
in the core intense, so that losses to Barkhausen noise would be reduced.
The primary and secondary would still see an AC field as the field
direction rotated.  I don't think this would reduce the Barkhausen noise
by much.  Whether the H-field vibrates or rotates, it would induce growth
and shrinkage of magnetic domains in the metal, and that causes heating.


> Question:  Is the synchronous motor (clock) a shaded pole motor?

I've seen big ones with "starter" coils.  They behave as conventional
induction motors until they get near the synchronous speed.  Since they
have a magnetically hard steel rotor, the rotor becomes permanently
magnetized and "locks on" to the AC b-field, at least they do if the
mechanical load is not too enormous.  Conventional non-synchronous
induction motors have magnetically soft rotors which constantly slip in
phase relative to the drive fields even when loaded normally.  Since even
a soft iron core can become a weak PM, I would expect that any induction
motor would become synchronous motor if the mechanical load on the rotor
was very small.




((((((((((((((((((((( ( (  (   (    (O)    )   )  ) ) )))))))))))))))))))))
William J. Beaty                                  SCIENCE HOBBYIST website
billb@eskimo.com                                  http://www.amasci.com
EE/programmer/sci-exhibits          science projects, tesla, weird science
Seattle, WA   206-789-0775          freenrg-L taoshum-L vortex-L webhead-L