The fan's motor, as far as I can tell, is an induction motor, which requires two separate phases for operation; however, we only have access to a single-phase line in our home and must therefore employ the use of a capacitor to convert the fan's connection to a two-phase one. Because of the energy storage capabilities of a capacitor, a single-phase connection can be converted into a dual-phase connection and used to power the fan.
Dear Sayeduzzaman
That's an interesting question to answer.
Well, the ceiling fan contains a single-phase induction motor which is inherently not a self-starting motor. it requires some external help for its start. Reason: for a three-phase power supply, a rotating magnetic field is developed that can rotate the rotor which is not the case in single-phase motors. For the single phase, there is only one phase available for stator winding which is unable to develop a rotating magnetic field. But any type of motor requires some magnetic field that can develop the initial torque to rotate the rotor.
Now here's the catch...
For any single-phase motor the stator winding is developing a field that is going positive and negative in a complete cycle. Hence making the net magnetic field as well as torque equal to zero. So there must be something in the circuit to avoid this situation.
Also, Fan will be confused to rotate in one direction (counterclockwise) during the positive cycle or the other way (clockwise) during the negative half cycle.
The capacitor when connected to the auxiliary stator winding of the fan, develops a 90-degree field that leads to the field of the main winding. Therefore, these two fields 90 degrees out of phase create a temporary 2-phase field system effect, that results in the rotating magnetic field or required initial torque to rotate the rotor or start the fan.
Once started the capacitor may be taken off, as now the rotor is rotating for each half cycle in the same direction due to a field created by the stator so the net field is not zero. It will continue running until we switch it off.
Hopefully, that answers your question.
Generally capacitors are used to store electrical energy as far i can think and they provide torque to fan when ever needed
In fact, the role of these capacitors is to:
- Reduce instabilities, by compensating its fluctuations (they charge during voltage peaks and discharge during drops);
-Suppress the offset (DC voltage added to a sinusoidal regime);
- Facilitate the starting of these motors which require a strong current at this precise moment.
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