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

Question: The angle between the rotating stator flux and rotor poles is called _________ angle.

• 1. synchronizing
• 2. obtuse
• 3. torque
• 4. power factor

Question: Slip-rings in a synchronous motor carry____________?

• 1. direct current
• 2. alternating current
• 3. no current
• 4. all of the above

Question: A synchronous motor working at leading power factor can be used as____________?

• 1. voltage booster
• 2. phase advancer
• 3. noise generator
• 4. mechanical synchronizer

Question: The standard full-load power factor ratings for synchronous motors are___________?

• 1. zero or 0.8 leading
• 2. unity or 0.8 lagging
• 3. unity or 0.8 leading
• 4. unity or zero

Question: The rotor copper losses, in a synchronous motor, are met by____________?

• 1. d.c. source
• 2. armature input
• 3. motor input
• 4. supply lines