Quiz Synchronous Motor 2025

For a synchronous motor Nm_??_Ns

• lower than

• higher than

• equal with

What is the key characteristic of a synchronous motor?

• It operates at variable speeds.

• It operates at constant speed regardless of the load.

• It operates only at high speeds.

• It operates only at low speeds.

How is the constant speed of a synchronous motor achieved?

• By using a single-phase AC supply.

• By interaction between a constant and a rotating magnetic field.

• By varying the load on the motor.

• By using a variable frequency drive.

What type of magnetic field does the rotor of a synchronous motor produce?

• A rotating magnetic field.

• A constant magnetic field.

• A pulsating magnetic field.

• No magnetic field.

What type of current is used to excite the stator of a synchronous motor

• DC

• Single Phase AC

• 3-Phase AC

• Pulsating DC

What is the synchronous speed of a motor determined by?

• The load on the motor

• The frequency of the AC supply.

• The voltage of the AC supply.

• The type of rotor used.

How is the rotor of a synchronous motor typically excited?

• By a three-phase AC supply

• By a single-phase AC supply.

• By a DC supply or permanent magnets.

• By an external mechanical force.

Why are synchronous motors not self-starting?

• They require a high starting torque.

• The rotor cannot initially synchronize with the rotating magnetic field.

• They operate only at low speeds.

• They require a single-phase supply to start.

What happens when the rotor reaches synchronous speed?

• The rotor locks with the rotating magnetic field.

• The rotor stops rotating.

• The rotor speed exceeds the synchronous speed.

• The rotor operates as an induction motor.

What happens if the load on a synchronous motor exceeds its capacity?

• The motor continues to operate at synchronous speed

• The motor slows down but does not stop.

• The motor falls out of synchronization and stops.

• The motor increases its speed to handle the load.