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- May 27, 2016
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You are right, and I should have been paying more attention about the centrifugal switch. There are "START" capacitors" and "RUN" capacitors, and often a motor can be provided with both. The "RUN" capacitor, if there, is usually smaller, might be connected internally, or not there at all!@graham-xrf
The only part missing is a description of the centrifugal switch.
In the video in post #1 the OP @AndySomogyi says that the motor DOES spin.
One small quibble; in post #25 you say:
Well, yes, kinda....the capacitor stays in circuit until the cetrifugal switch opens, and then it's out of the circuit.
It should never be switched out by an external switch.
I suspect that's what you meant.
-brino
Nearly all the induction motors with a fat capacitor on them, that I have ever had apart, were the way I described, meaning without any centrifugal switch. The motors that did have a speed switch were three-phase, with the switch changing them from a STAR connection for run-up, to a DELTA connection for full torque when at speed.
Andy's motor is a more sophisticated phase lag shifted type which exploits the different amounts of phase lag when at speed compared to when stopped. It is supposed to run smoothly without a start capacitor in circuit once it gets above a threshold RPM. I am thinking there really should be a "RUN" capacitor somewhere, but as you can see from the links, it is not necessarily so.
Dangerous to attempt, but some can be made to run in either direction, sans capacitor, by giving them a "flick" on the pulley. DON'T DO THIS !!!
There are dozens of complete explanations on the net.
Here are a couple.. --> LINK
--> LINK#2
For Andy, the centrifugal switch has to be working properly. I speculate, but if the contacts do not open at speed, or maybe only one leg disconnects properly, then the motor might be running rough because the capacitor remains connected when it should have let go. It sounds as if the switch is operating OK as the motor runs, and Andy has refurbished it, so we trust it is working.
I should mention that some motors which have a permanent capacitor and a separate switched start capacitor, might have a tapping on the S winding. Some motors have to start against a high load, and others are intended only to deliver torque once spinning fast.
Motor science has had decades beyond a century to develop. Getting into the phasor diagrams of motors, especially things like "wave-wound rotating field multipole", or "short-circuit 1-turn shaded pole start",gets incredibly mathematical and motor-nerdy. Let us not even get started on what happens when one adds in VFD drive electronics without knowing absolutely everything about the motor.
Thinking about it, the simple reference to the windings as "M", and "S" would stand for "MOTOR winding" and "START" winding.
Come to that, the whole discussion has so far (reasonably) assumed the motor is an induction type. There are types where the rotor makes itself magnetic with windings of it's own, fed from slip-ring connections.
I apologize for not getting to the centrifugal switch. The time difference had put me into the "wee small hours".
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