Alternators MCQs

Question 1

Three-phase alternators are invariably star-connected because

Accepted Answer

higher terminal voltage is obtained

Answer

less turns of wire are required

Answer

small conductors can be used

Answer

magnetic losses are the mainmum

Question 2

Which of the following conditions does not have to be met by alternators working in parallel?

Accepted Answer

The machines must have equal kVA ratings

Answer

Alternators must operate at the same frequency

Answer

Machines must have the same phase rotation

Answer

The terminal voltage of each machine must be the same

Question 3

The fictitious part of synchronous reactance takes care of

Accepted Answer

armature reaction

Answer

inductive reactance

Answer

voltage regulation

Answer

none of the above

Question 4

In an alternator the voltage of field system is usually

Accepted Answer

less than 200 V

Answer

more than 1000 V

Answer

between 40 V and 600 V

Answer

none of the above

Question 5

In an alternator, pitch factor is the ratio of the e.m.fs. of

Accepted Answer

short pitch coil to full pitch coil

Answer

full pitch winding to short pitch winding

Answer

distributed winding to full pitch winding

Answer

full pitch winding to concentrated winding

Question 6

Salient pole type rotors as compared to cylindrical pole type are

Accepted Answer

larger in diameter and smaller in axial length

Answer

small in diameter as well as axial length

Answer

large in diameter as well as axial

Answer

smaller in diameter and larger in axial length

Question 7

Which of the following relays come into operation in the event of the failure of prime-mover connected to the generator?

Accepted Answer

Reverse power relay

Answer

Buchholz relay

Answer

Differential relay

Answer

All of the above

Question 8

The per unlit vuaages of two synchronous machines connected through a lossless line are 0.95 L10? and 1.0 LO?. Match the two sides in the following

Accepted Answer

Real power of (P) Positive real power Machine

Answer

Reactive power of (Q) Positive reactive Machine power

Answer

Power factor of (R) Negative real Machine 1 power (S) Negative reactive power (T) Leading power factor (U) Lagging power factor

Question 9

A 100 MVA, 11 kV, 3-phase, 50 Hz, 8-pole synchronous generator has an inertia constant H equal to 4 seconds. The stored energy in the rotor of the generator at synchronous speed will be H= ?

Accepted Answer

800 MJ

Answer

100 MJ

Answer

400 MJ

Answer

12.5 MJ