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RE: potential sync. motor

If you use a belt to reduce the 11000 RPM by 3:1, you end up with 3666.67
RPM, not 3600.  Even if your motor's RPM was 10800, it would vary with load
and line voltage, and even if it was a synchronous 10800 RPM exactly (which
just isn't possible), the fact that you're using a belt and pulleys means
that the speed reduction is subject to the mechanical tolerances of the
pulleys, perhaps 2.99:1, so the rotor will quickly drift out of phase.  AND
even if you had a perfectly phase-locked 10800 RPM synchronous motor and a
perfect 3.000000000000000000:1 belt reducer, the belt will slip each time
you start the motor up, changing the phase of the rotor relative to the
mains.  Unless you use a speed and phase sensor on the rotor with active
feedback to control the motor RPM (which is non-trivial but has been done,
see Matt Behrend's site at
http://home.earthlink-dot-net/~electronxlc/construct/RSGcontroller.html), it
just won't work.

Regards, Gary Lau
Waltham, MA USA

-----Original Message-----
From: Tesla list [mailto:tesla-at-pupman-dot-com]
Sent: Wednesday, September 06, 2000 8:30 PM
To: tesla-at-pupman-dot-com
Subject: Re: potential sync. motor

Original poster: "Metlicka Marc" <mystuffs-at-orwell-dot-net> 


Tesla list wrote:

> Original poster: "Lau, Gary" <Gary.Lau-at-compaq-dot-com>
> Hi Marc:
> I hope you have some other use for this motor.  If the speed is 11000 RPM,
> there's no way this can be converted to the required 1800 or 3600 RPMs
> necessary for a sync RSG.

no, if you think about it, the blower is belt driven from the 3.5" disk at
ratio. i guess things must be explained thoroughly in all cases? sorry

> Regards, Gary Lau
> Waltham, MA USA