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RE: better sync motor mods?



Original poster: "David Dean by way of Terry Fritz <twftesla-at-uswest-dot-net>" <deano-at-corridor-dot-net>

Hi John,

I had a thought along the same lines a while back. This was probably in May
of last year, anyway just before I built my second sync rotary. I had
thought that rather than cutting a flat, why not mill a groove in the rotor
that is deep enough to cause the magnetic field which is induced in it to be
separated into "poles" without removing so much material as to cause the
current to increase as much as it would with the flats. I also thought that
the torque might not be diminished as much. I tried this on one motor, but
it would not lock in sync. once I had turned the grooves into flats of the
same depth, it worked as expected. I don't know if it would have worked if I
had made the grooves deeper. As far as cutting the current bars goes, it
seems to me that some have to be cut to get the thing to sync. I had
wondered if this might not be more the mechanism than the iron removal.

later
deano

> -----Original Message-----
> From: Tesla list [mailto:tesla-at-pupman-dot-com]
> Sent: Tuesday, January 09, 2001 2:05 PM
> To: tesla-at-pupman-dot-com
> Subject: better sync motor mods?
>
>
> Original poster: "by way of Terry Fritz <twftesla-at-uswest-dot-net>"
> <FutureT-at-aol-dot-com>
>
> Hello coilers,
>
> I inspected an old small commercial GE salient pole sync motor
> and noticed that the cuts in the armature are not flats, but "V" cuts.
> These V cuts are narrow and deep.  The top of the V is just half
> as wide as the uncut armature portion.  I don't know if more modern
> salient pole commercial motors are made this way.
>
> Maybe the flats that we amateurs grind onto the armatures
> are not the optimal shape for best torque, and cool running?
> Maybe we have to make the flats rather wide in order to make
> them deep enough?  If we used a V cut instead, we could make
> them deep without making them so wide.  This may improve the
> torque and let the motor run cooler.
>
> Certainly it is much harder to produce a V cut than a flat, so most
> coilers will probably want to continue using the flats which work
> fine anyway.  But it would be interesting to try the V cut idea,
> which could easily be accomplished with a milling machine.
> (It could be done with a hand file, but would be tricky.)  Perhaps
> someone with a milling machine or access to one will try this
> V cut idea.  For a true test, two identical motors would need to
> be modified, one with the V cut, one with the flat.  To picture
> better how the V cuts look....the view from the end of the armature
> looks much like a four leaf clover (maybe we'll be lucky too!).
>
> A possible problem with the V cut method is that it will probably
> cut though some of the imbedded current bars.  Since these
> bars are usually set at an angle, we may lose torque over a wider
> portion than we hoped to.  Maybe the GE motor has the current
> bars set perpendicular rather than angled to prevent this problem
> (details, details).
>
> Anyway, the V cut idea is something to ponder.  If the current
> bar issue is a problem, then maybe a concave dish-shaped cut would
> be better.  It produces a deeper cut for a narrower width than a
> flat cut.
>
> Mod'ing for max torque,
> John Freau
>
>
>