Why Capacitor is used in Single phase Induction Motor?Full Explanation.

Why Capacitor is used in Single phase Induction Motor?


Nowadays single phase motors are widely used in our house, office and other areas. Single phase motor becomes very popular as it is low cost. 

There are three types of Single Phase motor

  1. Induction motors
  2. Commutator motors
  3. Synchronous motors

You may notice that every single phase induction motor (except Shaded pole Induction Motor) need one or more capacitor. So today we are going to know Why Capacitor is used in Single-phase Induction Motor? or Why Capacitor is used in Fan?







Why Capacitor is used in Single-phase Induction Motor: The answer is that as the single-phase induction motor is not self-starting so the capacitor is used to make single phase induction motor self-starting.


Why Single Phase Induction Motor is not self-starting?


The Single Phase Induction Motor is not self-starting because if we give single phase AC supply to the stator winding of the single-phase induction motor the stator winding produces alternating flux and for the transformer action, an alternating emf is produced on the rotor winding which causes to flow alternating current in the rotor winding. 

So an alternating flux also produced in the rotor winding which tried to oppose the stator emf. Therefore no torque will develop in the rotor. So when we give single phase AC supply the motor not start rotating it will vibrate. So for this reason capacitor is used in Ceiling Fan as well as any single phase induction motor.


How to start a single phase induction motor?


After giving the single phase AC supply if we push the rotor by hand or by another means in either direction, it will pick up the speed and continue to rotate in the same direction developing operating torque.


How the Capacitor make the single-phase induction motor self-starting?


To make the single phase induction motor self-starting we need to add an extra winding which is called starting winding. And the winding will be connected in series with a capacitor. By using a capacitor of proper value, the starting winding current can be made to lead the main winding current by 90o. That means the capacitor creates a phase difference between the two windings and the starting winding push the rotor to start rotating.

Single Phase motor connection with Capacitor Diagram:


The below circuit diagram is of the Permanent Capacitor single phase Induction motor. This is also the circuit diagram of a ceiling fan.


Why Capacitor is used in Single phase Induction Motor, Single Phase motor connection with Capacitor Diagram, Why Single Phase Induction Motor is not self starting




What type of motor used in Ceiling Fan?

Single phase squirrel cage capacitor start capacitor run induction motor used in Ceiling Fan.


How to connect the capacitor with the ceiling fan?


At first measure the resistance of each winding. The starting winding has less resistance than running winding. Then connect the capacitor according to the above circuit diagram.



Which type of Capacitor used in Ceiling Fan?

Mainly Oil filled capacitor used in ceiling Fan. Nowadays, the dry capacitor with high insulation used in the ceiling fan. 








How to change the direction of rotation of single phase induction motor?

To change the direction of rotation of single phase induction motor reverse the connection of any one winding either starting winding or running winding.



Which type of single phase induction motor can run without capacitor?

The shaded pole induction motor can run without the capacitor.




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Why Capacitor is used in Single phase Induction Motor?Full Explanation. Why Capacitor is used in Single phase Induction Motor?Full Explanation. Reviewed by ETechnoG on 07:53 Rating: 5
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