Why Single Phase Induction Motor is not Self Starting?
A single-phase induction motor lacks a naturally rotating magnetic field, which makes it non-self-starting. Unlike three-phase motors that generate a rotating magnetic field with three alternating currents, single-phase motors rely on a single alternating current that produces a pulsating magnetic field. This field is unable to initiate continuous rotation in the motor’s rotor due to its non-uniform nature and inability to provide sufficient starting torque.
At the starting condition of the motor, both φf (forwarding component of alternating flux(φm)) and φb(backward component of alternating flux(φm)) are equal in magnitude but opposite in direction. They cancel each other out, which results zero net torque on the rotor. This zero torque at the starting condition is why single-phase induction motors are not self-starting.
To overcome this limitation, various techniques are used, such as adding an auxiliary winding and a capacitor to simulate a rotating magnetic field during startup or using centrifugal switches to disconnect the starting winding once the motor reaches a certain speed. These methods help single-phase induction motors achieve the necessary torque for self-starting and sustained operation.
Single Phase Induction Motor
A single-phase induction motor is a small-size motor with a fractional-kilowatt rating. They work on the principle of electromagnetic induction to create a rotating magnetic field. It is used in domestic appliances like fans, hair dryers, washing machines, vacuum cleaners, mixers, refrigerators, food processors and kitchen equipment employ these motors.
- Construction of Single-Phase Induction Motor
- Components of Single-Phase Induction Motor
- Operation and Working of Single-Phase Induction Motor
- Application of Single-Phase Induction Motor
- Advantages of Single-Phase Induction Motor
- Disadvantages of Single-Phase Induction Motor
- Solved examples on Single-Phase Induction Motor