MCQs on Synchronous Motor

What is the principle of operation of a synchronous motor?

• Electromagnetic induction

• Interaction between a rotating magnetic field and a stationary magnetic field

• Lenz's law

• Faraday's law of electromagnetic induction

What is the synchronous speed of a 4-pole, 50 Hz synchronous motor?

• 1000 rpm

• 1500 rpm

• 3000 rpm

• 750 rpm

What is the power factor of a synchronous motor?

• Always lagging

• Always leading

• Can be leading, lagging, or unity

• Always unity

What is the purpose of damper windings in a synchronous motor?

• To improve the power factor

• To provide starting torque

• To stabilize the rotor

• To reduce losses

How is a synchronous motor started?

• By directly connecting it to the supply

• By using a starter motor

• By using a pony motor

• By using damper windings and external excitation

What is the effect of increasing the field excitation of a synchronous motor?

• Increases the power factor

• Decreases the power factor

• Has no effect on the power factor

• Increases the speed

What is the V-curve of a synchronous motor?

• A plot of armature current vs. field current at constant load

• A plot of power factor vs. field current at constant load

• A plot of speed vs. field current at constant load

• A plot of torque vs. field current at constant load

What is the effect of increasing the load on a synchronous motor?

• The rotor speed increases

• The rotor speed decreases

• The rotor speed remains constant

• The rotor speed fluctuates

What is the maximum power output of a synchronous motor?

• When the load angle is 0 degrees

• When the load angle is 90 degrees

• When the load angle is 180 degrees

• When the load angle is 45 degrees

What is the synchronous condenser?

• A synchronous motor running at no load

• A synchronous generator running at no load

• A device to improve the power factor

• A device to regulate the voltage