Electronic – Motor Run Capacitor Optimal Size

capacitormotor

My understanding of motor run capacitors is that there is an optimal value for a paticular motor and that if it is not matched exactly, the magnetic field will vary and cause the motor to run poorly. Is this correct?

If yes, then how accurate does the capacitor size need to be? 10%? %5?

Best Answer

They're typically marked +/-5% tolerance, so that should give you some idea of what is expected. Here is a (somewhat) detailed article on motor run capacitors.

When they are damaged they tend to drop in capacitance.

From a motor manufacturer, a graph that comes closer to answering your question but does not really tell you how much temperature derating you'll have to do etc.

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For example, if the capacitor is too low and the motor stalls it may overheat because it's not cooling itself, depending on the design.

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