Tape Recorder Motor - Capacitor

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Old 01-04-11, 10:01 PM
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Tape Recorder Motor - Capacitor

I appreciate DaveB and Wgoodrich's motor discussion from year 2002. It helped me, below.

My situation is a drive motor in an older reel-to-reel tape recorder that was running hot. Got up to 153 degF after 45 minutes of operation, unloaded. It has two sets of windings, one tied in with a 2 microfarad capacitor. No centrifugal switch nor starting capacitor.

Their discussion on counter EMF (electromotive force) and how it decayed over time in a bad motor so that current increased answered my questions on what I saw. I found this motor also slowed from 3469 rpm, cold, to 2800 rpm, hot. So I digged into it and found one of the pair of windings burned.

I want to get this running so will need to rewind. The discussion on how the capacitor helps running torque answered my question on why it was there.
 
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Old 01-07-11, 09:40 AM
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Capacitor function in a motor without a centrifugal switch

DaveB: Assuming this gets to your e-mail account written in 2002 so that you'll read it in 2011, how does a capacitor function in a two-winding single phase motor that doesn't switch out the capacitor, without a centrifugal switch? Such is found in a reel-to-reel tape recorder.

Am I correct to assume the 2nd winding, 90 degrees out of phase with the main winding, has a capacitor in series with it so that it helps maintain constant torque and such torque is more than in a single winding single phase motor? Does it counter the inductive reactance of this 2nd winding, like you explained for a motor with a centrifugal switch switching out the start winding? It helps the start winding look solely like resistance? DBabbitt
 
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