Electrical Machines Mock Test 6

10%

Question 1 of 10

1. At synchronous speed, relative speed between rotating air-gap flux and damper is?

more than zero

zero

lesser than Ns

Question 1 of 10

Question 2 of 10

2. Series capacitors will improve the ___________

Stiffness

SSSL

Hunting

Transient stability

Question 2 of 10

Question 3 of 10

3. When the rotor speed becomes greater than synchronous speed, which type of torque is produced in damper winding?

Induction generator

Reluctance motor

Induction motor

Synchronous generator

Question 3 of 10

Question 4 of 10

4. The operating frequency and voltage of an isolated alternator ________ if the prime mover input to motor is increased.

remains constant

no relation exists between the power and frequency

increases

decreases

Question 4 of 10

Question 5 of 10

5. Electromagnetic torque is present in rotating machines when ____________

rotor windings carry current

any of the mentioned

stator windings carry current

both stator and rotor windings carry current

Question 5 of 10

Question 6 of 10

6. for a synchronous motor, its power factor __________

increases with loading for a given excitation

is independent of its excitation

decreases with increase in excitation

improves with increase in excitation and may even become leading at higher excitations

Question 6 of 10

Question 7 of 10

7. Consider a 3-phase cylindrical-rotor alternator.

A. E.m.f. generated by armature reaction lags armature current by 90°.
B. Air gap voltage leads the field flux by 90°
C. Air gap voltage lags the field flux by 90°    
D. Armature reaction mmf lags the field flux by (90°+ internal p.f. angle)

A, C, D C) B, D D) C, D

A, B, D

Question 7 of 10

Question 8 of 10

8. A synchronous machine with its field winding on stator and polyphase armature winding on rotor. At steady state, its air gap field is?

I. stationary w.r.t. stator 
II. rotating at double the speed Ns w.r.t. rotor
III. rotating in direction opposite to rotor

I, II, III

II, I

II, III

Question 8 of 10

Question 9 of 10

9. Which motor can conveniently operate at lagging as well as leading power factor?

Synchronous motor

Squirrel cage induction motor

Stepper motor

Slip ring induction motor

Question 9 of 10

Question 10 of 10

10. In which one of the following is reluctance power developed?

Non-salient pole alternator

Squirrel cage rotor type induction motor

All of the mentioned

Salient pole alternator

Question 10 of 10