Capacitor Basics

Why is capacitor needed for a motor? Capacitor is needed for a motor for starting and also is used for keeping a motor from running. To help you understand, think of a motor at rest first. The  motor capacitor provides extra winding for the circuit to run. It stores charge, then releases that stored electrical charge to help start an electrical motor (starting capacitor). In short, it gives the motor a "start up". Then it gets disconnected after the motor reaches a certain speed.

However, in case the motor drops below a required speed, another capacitor switches back into electrical circuit and to keep it from spinning (run capacitor).


Now that capacitor is explained, how can we test it if it is a good capacitor or not?
Well, the most common and recommended way is the use of multitester.


As per electrical standards, we can measure if there is electrical resistance. As per sample photo, we can see that there are 3 terminals - for F for, Herm (hermetic compressor) and the third is C for common. First make sure tester is in zero amps when the positive and negative probes are connected. After that, check resistance of the folowing : Common-fan and Common-herm. If there is still a resistance, then it is a good capacitor.