DIYbanter - Is it bad for 3 phase motor to start/stop frequently?

On Sun, 12 Mar 2006 00:01:48 GMT, Alex wrote:

Is it bad for 3 phase motor to start/stop frequently?
I have 2HP TEFC Leeson 1725 RPM

Depends on the loading and duty of the motor - what do you plan to do
with it? And how often is 'frequently'? As others said, there are
ratings on the individual motors as to 'how much is too much'. You
can call Leeson with the spec numbers off the motor nameplate and ask.

For air compressors, they shouldn't be starting more than 5 or 6
times an hour on a normal basis - if they are, you have one or more of
these problems: the differential or set point on the pressure switch
is set too low (like on at 90 off at 100), not enough compressor
output volume (CFM), or not enough receiver tank volume (Gal/CF).

Shop compressors can be set to run the motor continuously and unload
the compressor if it's /almost/ big enough for the job.

Odd thought to consider that may prove valuable:

Don't get stuck in the mindset that the only mover for a particular
job HAS to be an electric motor - Some jobs are better served through
hydraulics or pneumatics, where the working motor is free to start and
stop unrestricted as often as it likes, and the prime mover (pump or
compressor) can either run continuously and unloaded between cycles,
or stop periodically and run the equipment off a receiver tank or
accumulator during the 'rest periods'.

And an air motor can sit there locked-rotor with air on it all day
without damage. (As long as the rest of the gear can take the torque
without breaking, naturally.) A hydraulic motor can too, as long as
there's a relief valve for the pump and proper fluid cooling. But try
that with an electric motor...

-- Bruce --

--
Bruce L. Bergman, Woodland Hills (Los Angeles) CA - Desktop
Electrician for Westend Electric - CA726700
5737 Kanan Rd. #359, Agoura CA 91301 (818) 889-9545
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