Can a single-phase motor run without a capacitor?


There are three common types of single-phase motors named capacitor motor, shaded pole motor and split phase motors.

Shaded pole and split phase single-phase motors do not require a capacitor to run. While capacitor motors run with the help of capacitors. Capacitor motors also have different types based on the role of a capacitor. A few of them are been discussed below.

Capacitor Start Motor

In the capacitor start motor, as cleared from name too, the role of the capacitor is to start the motor. So the capacitor is their just to provide the initial torque to the rotor by adding phase difference to the rotor magnetic field. If the capacitor is been removed from this kind of motor, then it will not start rotating when power will be applied to the stator winding, as initial torque will be missing. However, after applying power, if someone provides that initial push to the rotor manually from the external rotor shaft, then the motor will start running and will remain running until power is been connected with the stator winding. Again, at the next start, the external push will be required to start the rotation of the motor.

Capacitor Run Motor

This type of motor capacitor is permanently connected in series with the start winding and provides torque all the time. Therefore, this type of motor will not be able to run without a capacitor even after applying an initial push.

Capacitor Start Capacitor Run Motor

In this type of motor, there are two separate capacitors for starting and for the running. The starting capacitor is to provide a starting push while running the capacitor is for providing extra torque while running. This motor is a mixture of the previous two types, i.e. Capacitor starts motor and capacitor start capacitor run the motor. This type of motor will require both the capacitors for proper operation. However, just like the capacitor type, this motor start will be able to run with external push, in case the start capacitor is missing or faulty.

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