Single Phase Induction Motor Questions and Answers for Viva

Answer-1: A Single Phase Induction Motor is an AC motor that operates on a single-phase power supply and is commonly used in household appliances and small industrial applications.

Answer-2: The main components include a stator (with main and auxiliary windings), a rotor, bearings, and a frame.

Answer-3: Single Phase Induction Motors work on the principle of electromagnetic induction. When an alternating current flows through the stator winding, it produces a rotating magnetic field that induces currents in the rotor, causing it to rotate.

Answer-4: The different types include capacitor start, capacitor start-capacitor run, shaded pole, and split-phase motors.

Answer-5: The direction of rotation can be changed by reversing the connections of either the main winding or the auxiliary winding.

Answer-6: Single Phase Motors are simpler and cheaper but have lower efficiency and power compared to Three Phase Motors.

Answer-7: They are used in household appliances like fans, washing machines, air conditioners, and small industrial machines.

Answer-8: Common starting methods include Capacitor Start Induction Run (CSIR), Capacitor Start Capacitor Run (CSCR), and Split Phase.

Answer-9: In a CSIR motor, a capacitor is used only during starting to provide an additional phase shift for starting torque. In a CSCR motor, capacitors remain in the circuit during both starting and running to improve efficiency.

Answer-10: The capacitor is used to create a phase difference between the main and auxiliary windings, which helps in starting and running the motor efficiently.

Answer-11: A Split Phase Motor uses two windings: the main winding and the starting winding. The starting winding is disconnected by a centrifugal switch once the motor reaches a certain speed.

Answer-12: Speed control methods include changing the supply frequency using a variable frequency drive (VFD) or using mechanical methods like changing pulley sizes.

Answer-13: Efficiency is calculated as the ratio of output power to input power, typically measured using a wattmeter.

Answer-14: The maximum power factor of a Single Phase Induction Motor is unity (1).

Answer-15: The efficiency of a Single Phase Induction Motor typically ranges from 50% to 70%.

Answer-16: In capacitor start motor, capacitor is connected in series with the starting winding. But it will be  disconnected  fro m  the  supply,  when  the  motor  picks  up  its  speed.  But in capacitor start capacitor run motor starting winding and capacitor are not disconnected, but always connected in the supply, so it has high starting and running torque.

Answer-17: Regular maintenance, proper lubrication, and avoiding overloading can help increase the lifespan of the motor.