Pure 3 Phase IM

What is the basic principle of operation of a three-phase induction motor?

• a) The motor operates on direct current.
• b) The motor operates by producing a rotating magnetic field that induces current in the rotor.
• c) The motor operates using a fixed magnetic field.
• d) The motor requires external power for starting.

Which of the following components is essential for creating a rotating magnetic field in a three-phase induction motor?

• a) Slip ring
• b) Stator windings
• c) Capacitor
• d) Rotor

What type of rotor is typically used in most three-phase induction motors?

• a) Squirrel cage rotor
• b) Wound rotor
• c) Permanent magnet rotor
• d) Brushless rotor

What is the function of the rotor in a three-phase induction motor?

• a) To produce a rotating magnetic field.
• b) To generate the current which interacts with the stator's magnetic field.
• c) To convert electrical energy into mechanical energy.
• d) To store energy for future use.

In a three-phase induction motor, what is the term used to describe the difference in speed between the rotor and the rotating magnetic field?

• a) Slip
• b) Frequency
• c) Torque
• d) Phase difference

What does the slip of a three-phase induction motor indicate?

• a) The speed of the rotor relative to the stator field.
• b) The efficiency of the motor.
• c) The input voltage to the motor.
• d) The phase angle of the current.

At what condition does a three-phase induction motor operate at synchronous speed?

• a) When the rotor is stationary.
• b) When the motor is loaded to full capacity.
• c) When the rotor speed equals the speed of the magnetic field.
• d) The motor never operates at synchronous speed.

What is the power factor of an induction motor when it is unloaded?

• a) Zero
• b) Unity
• c) Very low
• d) Very high

Which of the following is true for the starting torque of a three-phase induction motor?

• a) It is always zero.
• b) It is high during startup and decreases with time.
• c) It is low during startup and increases with time.
• d) It is high at synchronous speed.

What is the typical efficiency range of a three-phase induction motor?

• a) 30% to 50%
• b) 50% to 70%
• c) 70% to 95%
• d) 95% to 100%