Re: mod of sync motor (trying to modify)

To: tesla-at-pupman-dot-com
Subject: Re: mod of sync motor (trying to modify)
From: FutureT-at-aol-dot-com (by way of Terry Fritz <twftesla-at-uswest-dot-net>)
Date: Mon, 27 Mar 2000 11:21:28 -0700
Approved: twftesla-at-uswest-dot-net
Delivered-To: fixup-tesla-at-pupman-dot-com-at-fixme

In a message dated 3/26/00 2:59:41 PM Pacific Standard Time, 
MAILER-DAEMON-at-aol-dot-com writes:

> Somewhat less than stellar performance. 
>  
>  I found 4 positions, 90 degrees apart that the motor wouldn't start
>  from. I could also get the motor to spin in either direction if I
>  "helped" it spin up. When running, it didn't run very smoothly and 
>  got a little warmer that it should. Under the florescent light it 
>  gave no indication of synchronization. At this point, I don't know
>  if I cut too much, or not enough. If I didn't cut enough I can cut
>  some more and try it again. If I cut too much, the motor is trash. 
>  Seeing that this motor was a test case anyway, I'll be milling off 
>  a bit more on Monday just to see what happens.
>  
>  
>  Anybody have any thoughts on what went wrong here???
>  
>  Paul
>  
Paul,

usually the cut and uncut areas must be about equal, with the cut
areas a little smaller maybe than the uncut areas, so if you have
not gone beyond "equal" for the cut and uncut, then the motor is
still OK.  There's leeway here anyway.   This motor may need a
capacitor to start and run properly.  Once you add the cap, it
may self start easily from any position.  Some motors have a built
in start switch (centrifigal) that disconnects the capacitor after the
motor has come up to speed.  these types usually require a larger
start cap.   But usually the smallest motors (1/40HP) are not this
type, and have the cap permanently attached.

Usually if the motor is not synced (locked), it will not sound very
steady when it's running.  When it's synced it will sound very steady.
One you're used to these motors, you can often tell by listening whether
they're locked.

Often one of the wires is shared between power and the capacitor, I
forget how many wires you said you had there.  The lowest resistance
winding should be the main winding for direct connection to the AC.

Is this Robbins and Myers brand?  Anyway, I don't use the dead pole
method for modifying my motors, but rather the proportion of cut and
uncut areas.  For a given HP rating, some motors seem much stronger
than others depending on the manufacturer.  BTW, usually a 1/4HP
motor is about the same size as a 1/3HP motor, and the 1/40 HP motor
will be much smaller.

Cheers,
John Freau