Question

Which of the following statements is INCORRECT for a polyphase induction motor?
1. It is also called asynchronous machine
2. Stator winding is directly connected to the a.c. source
3. It is a singly excited a.c. machine
4. Rotor winding is directly connected to the a.c. source

Answer 1

Correct Answer - Option 4 : Rotor winding is directly connected to the a.c. source

Three-Phase AC Induction Motor:

• The three-phase AC induction motor is a rotating electric machine that is designed to operate on a three-phase supply.
• The principle of operation of this motor is based on the production of a rotating magnetic field.
• This 3-phase motor is also called as an asynchronous motor.
• Mostly 3-phase supply is given to stator winding.
• There is no supply given to the rotor, So called Singly-Excited.
• These AC motors are of two types: squirrel and slip-ring type induction motors.
• The rotor speed is not equal to synchronous speed, so it is called as asynchronous motor.

Therefore INCORRECT option will be ‘Rotor winding is directly connected to the AC source’