Question: The magnitude of field flux in a 3-phase synchronous motor?

• 1. varies with power factor
• 2. varies with speed
• 3. varies with the load
• 4. remains constant at all loads

Question: The ratio of starting torque to running torque in a synchronous motor is____________?

• 1. zero
• 2. one
• 3. two
• 4. infinity

Question: The induced e.m.f. in a synchronous motor working on leading power factor will be_____________?

• 1. more than the supply voltage
• 2. less than the supply voltage
• 3. equal to the supply voltage
• 4. None of these

Question: Which of the following resistances can be measured by conducting insulation resistance test on a synchronous motor ?

• 1. Phase to phase winding resistance
• 2. Stator winding to earthed frame
• 3. Rotor winding to earthed shaft
• 4. All of the above

Question: The speed of a synchronous motor:

• 1. increases as the load increases
• 2. decreases as the load decreases
• 3. always remains constant
• 4. none of the above

Question: When a 3-phase synchronous generator is supplying a zero power factor lagging load, the armature field affects the main field in the following way:

• 1. augments it directly
• 2. directly opposes it
• 3. cross-magnetises it
• 4. none of the above

Question: If in a synchronous motor, driving mechanical load and drawing current at lagging power factor from constant voltage supply, its field excitation is increased, then its power factor__________?

• 1. become more
• 2. become less
• 3. remain constant
• 4. none of the above

Question: Change of D.C. excitation of a synchronous motor changes:

• 1. applied voltage of the motor
• 2. power factor of power drawn by the motor
• 3. motor speed
• 4. none of the these

Question: The mechanical displacement of the rotor with respect to the stator, in polyphase multipolar synchronous motors running at full load, is of the order of_____________?

• 1. zero degree
• 2. two degrees
• 3. five degrees
• 4. ten degrees

Question: An important advantage of a synchronous motor over wound round induction motor is that:

• 1. its power factor may be varied at will
• 2. its speed is independent of supply frequency
• 3. its speed may be controlled more easily
• 4. none of the above