Reply by Tennessee

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Posted on Do I need a new start capacitor?

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2873 posts in 2513 days

#1 posted 11-06-2012 07:17 PM

Ok, I phrased it slightly wrong. The capacitor is there to give an inrush in direction, which it does over and over as it charges and discharges. It also keeps the magnetic field slightly ahead of the rotor, causing it to “chase the magnetic field”, so the motor comes up to speed. If the rotor cannot keep up due to faulty bearings, excessive load, etc, the current rises, and the breaker trips. That is why when the cap is bad, you can still make the motor go one way or another by giving it a spin. (In some cases) You are advancing the magnetic field in a particular direction and the rotor will follow the magnetic field, since we’re dealing with AC.
But it is responsible for the first directional current inrush to make the motor go one way or another, depending on how the cap is wired in the circuit.
Also in my experience, caps don’t go bad slowly. Once they short across their any of their plates internally, the party is pretty much over at those amperages.

-- Tsunami Guitars and Custom Woodworking, Cleveland, TN

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