Question: A synchronous motor will always stop when:______________?

• 1. supply voltage fluctuates
• 2. load in motor varies
• 3. excitation winding gets disconnected
• 4. supply voltage frequency changes

Question: The speed regulation of a synchronous motor is always___________?

• 1. 1%
• 2. 0.5%
• 3. positive
• 4. zero

Question: . In a synchronous motor which loss varies with load ?

• 1. Windage loss
• 2. Bearing friction loss
• 3. Copper loss
• 4. Core loss

Question: For V-curves for a synchronous motor the graph is drawn between:_______________?

• 1. armature current and power factor
• 2. terminal voltage and load factor
• 3. power factor and field current
• 4. field current and armature current

Question: An over-excited synchronous motor takes__________?

• 1. leading current
• 2. lagging current
• 3. both A and B
• 4. none of the above

Question: The synchronous motor is not inherently self-starting because_______________?

• 1. the force required to accelerate the rotor to the synchronous speed in an instant is absent
• 2. the starting device to accelerate the rotor to near synchronous speed is absent
• 3. a rotating magnetic field does not have enough poles
• 4. the rotating magnetic field is produced by only 50 Hz frequency currents

Question: When V is the applied voltage, then the breakdown torque of a synchronous motor varies as_________?

• 1. V
• 2. V312
• 3. V2
• 4. 1/V

Question: A three-phase synchronous motor will have_____________?

• 1. no slip-rings
• 2. one slip-ring
• 3. two slip-rings
• 4. three slip-rings

Question: In case one phase of a three-phase synchronous motor is short-circuited the motor will____________?

• 1. not start
• 2. run at 2/3 of synchronous speed
• 3. run with excessive vibrations
• 4. take less than the rated load

Question: Synchronous motors are generally not self-starting because:

• 1. the direction of rotation is not fixed
• 2. the direction of instantaneous torque reverses after half cycle
• 3. startes cannot be used on these machines
• 4. starting winding is not provided on the machines