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Posted by Dave Martindale on July 6, 2007, 1:10 pm
>I have a 3/4 HP pool pump motor that has a centrifugal switch in it.
>The start windings have gone bad so it will not start on its own but
>will run fine if I "give it a hand" to get started. My question is
>can I put a start capacitor on the main windings to get it going? Will
>it work? What size capacitor should I try? Capacitor are far cheaper
>than pool pumps so giving it a try would be a low bux solution.
If the winding is bad, the motor is dead.
Capacitor-start and capacitor-run motors put the capacitor in series
with a second winding. The capacitor causes a phase shift in the
current in the second winding so that the magnetic fields of the
(unshifted) main winding and the second winding (added together)
rotates. A split phase motor gets the phase shift by making the second
winding higher resistance or higher inductance, without a capacitor.
But all of these methods need the second winding to work. With one
single winding, there is no rotating magnetic field, just a pulsating
one. That will keep the motor rotating once started, but won't start
it. A capacitor on the main winding will cause a phase shift with
respect to incoming power, but there's still no rotating field.
He's dead, Jim - unless you get a motor shop to repair or rewind the
start winding.
Dave
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