SOLUTION

In single-phase electric induction motors generally two separate sets of windings are used, Viz. main and auxiliary winding. A capacitor is used in series with auxiliary winding to create a phase difference between the currents of the two windings. This in turn creates a rotating magnetic held around the rotor, making it rotate.

Some motors use high-value capacitors in auxiliary windings only during the starting, which are disconnected through a centrifugal switch once the motor attains the required speed. These are mostly of electrolytic type and are called motor start capacitors. Capacitor-start capacitor-run motors are also commonly employed.

There are generally three different reasons why a capacitor is used with a ceiling fan or motor:

(a) The capacitor is used to give a phase shift and create a rotating magnetic field, so the motor will start turning more easily, against the inertia of the blades or load.

(b) It is sometimes used in speed control circuitry.

(c) The capacitor may be used for power factor correction.

(d) A capacitor-start induction motor has a non-polarized electrolytic capacitor in series with the auxiliary winding during starting, which is disconnected once the motor starts.

(e) A capacitor-start capacitor-run motor typically has a large non-polarized electrolytic capacitor in series with the auxiliary winding for starting, then a smaller non-electrolytic capacitor during running. An electrolytic capacitor has no polarity marking.