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Sync Motors
From: teslaman-at-juno-dot-com[SMTP:teslaman-at-juno-dot-com]
Sent: Tuesday, September 23, 1997 8:31 PM
To: tesla-at-pupman-dot-com
Subject: Re: Sync Motors
On Tue, 23 Sep 1997 17:45:46 -0500 Tesla List <tesla-at-pupman-dot-com> writes:
>
>From: FutureT-at-aol-dot-com[SMTP:FutureT-at-aol-dot-com]
>Sent: Tuesday, September 23, 1997 6:44 AM
>To: tesla-at-pupman-dot-com
>Subject: Re: Sync Motors
>
>In a message dated 97-09-22 22:22:05 EDT, you write:
>
><<
>> Question: Can squirrel-cage type motors be modified to become
>> synchronous? I have two 40W motors which use a cap winding for
>> generating the extra phase (no switching) and the armature has
>> conductors embeded in laminated iron.
>
>> Thanks,
>> Malcolm
> >>
>
>Malcolm,
>
>In general, yes, but I've never tried
>using the types that keep the cap in place all the time. It would
>seem that the extra phase would want to see its own flats, such
>that a 3600 rpm motor would want to see four flats instead of
>the usual 2 flats? And an 1800 rpm motor may want to see
>8 flats instead of the usual 4? I think the modification would
>work, since these are induction motors...the question is how
>many flats would be needed. I too have wondered about this,
>I hope someone knows the answer. Also, these 40 watts motors
>may be kind of weak for a sync-gap?
>
>I have modified standard squirrel cage induction motors without
>the run caps, and they work excellently in sync mode. You may
>have seen my recent posts on the subject. The smallest motor
>I have used is 1/10 HP, and this locks up a 6" disc with narrow
>edge electrodes (3600 rpm). Kevin E. uses 1/20 HP motors. I
>don't know if Kevin's motors use the run cap. Maybe he'll have
>some comments. Washing machine and clothes dryer motors
>are good and can be torn out of junked units. These are usually
>1/4 or 1/3 HP.
>
>Hope this helps,
>
>John Freau
>
>
>Malcom, John..
>
The motor in question sounds like a permanent capacitor, split phase
(P.S.C) motor which I have modified several of. All single phase a/c
induction motors need at least 2-phases to start the armature rotation.
Most use capacitance to simulate a second phase which is 90 electrical
degrees from the main field winding. I like the P.S.C.motors because
there are no internal or external switches to deal with. 40
watts should be in the 1/20 to 1/15 H.P. range which will spin a 7" x
1/4" disk and 2-electrodes from experience. With 3600 R.P.M. it will
need 2-flats, if 1800 R.P.M. then 4-flats would be required. I
personally like the 3600 motors to modify because there won't be as much
power lost as in modifying a 1800 R.P.M motor. There will also be more
air flow over the electrodes with the higher speed.
Kevin E.