Re: Rotor & sync motor
From: Edward V. Phillips[SMTP:ed-at-alumni.caltech.edu]
Sent: Tuesday, September 16, 1997 12:52 PM
Subject: Re: Rotor & sync motor
"Some information on the internet says 4 flats can be milled in the armature
to make a 1750 RPM run sync. Most AC motors are 1725 RPM. My question is,
will this work on a 1725 RPM motor? My next question is, will the flats make
a 1725 RPM motor run at 1800 RPM?
My friend at the motor shop said he thought the flats would make a 1725 RPM
motor sync at exactly 1725 RPM's. And a 1750 RPM motor would sync at 1750
RPM. But it seems to me like the flats will have to sync with the 60 Hz AC
and run exactly 1800 RPM's. Has anyone tried this? Does this really work?
I have a 1/4 HP 1725 RPM 120 VAC motor I can use to make a sync motor. If
this really works I will mill flats in the armature and use the motor on a
Yes, suitable flats on the 1725 RPM motor will let it work
at 1800 RPM, PROVIDED enough torque is generated to pull it into
synchronous speed. The speed of a sync motor is set by the number of
poles and the line frequency, not the nameplate speed. Latter, however,
tells you how many poles.
"I called my friend at the motor shop about a sync motor. He said they don't
make sync motors any more with out special order and they are very
expensive. True sync motors have a wound armature with slip rings and
Not so. Some do and some don't! Plenty of sync motors out
there, I'll bet, and plenty are still being made.