# Objective Questions on Alternators | Part 4

- Link: https://studyelectrical.com/2014/01/objective-questions-on-alternators-4.html
- Published: 2014-01-18T09:57:00+00:00
- Author: 

46. The windings for an alternator are

 * I. 36 slots, four poles, span 1 to 8
 * II. 72 slots, six poles, span 1 to 10
 * III. 96 slots, six poles, span 1 to 12.

The windings having pitch factors of more than 0.9 are
  (A) I and II only (B) II
and III only (C) I and II only (D) I, II and III.

Questions 47 to 48 refer to the data given below:

> ** A 500 kVA ,2300 volt three phase star connected alternator has a full load 
> armature-resistance drop per phase of 50 volts and a combined armature reactance
> plus armature-reaction drop of 500 volts per phase**

 47. The percent regulation of the alternator at unity power factor is  (A) 1.05(
B) 10.5 (C) 21.5 (D) 27.5.

48. The percent regulation of the alternator at 0.866 power factor lagging is
  (
A) 26.3 (B) 20.1 (C) 16.6 (D) 10.5.

   49. The percent regulation of the alternator at 0.8 power factor leading is  (
A) 13.2 (B) 26.4 (C) – 26.4 (D) – 13.2.

50. The imaginary or fictitious part of synchronous reactance takes care of
  (A)
armature reaction (B) voltage regulation (C) inductive reactance (D) none of the
above.

51. In an alternator, the use of short pitch coils of 160° will indicate the absence
of
  (A) third harmonic (B) fifth harmonic (C) seventh harmonic (D) ninth harmonic.
52. When a generator designed for operation at 60 Hz is operated at 50 Hz  (A) operating
voltage must be derated to (50/60) of its original value (B) operating voltage must
be derated to (50/60)2 of its original value (C) kVA rating can be upgraded to (
60/50) of the rated value (D) the generator will not take any load.

   53. Overheating of generator’s winding  (A) reduces generated voltage (B) reduces
power factor (C) reduces life of the machine (D) does not have any significant effect.
54. Rotor shaft of 500 MW alternator is supported in  (A) ball bearings (B) roller
bearings (C) needle bearings (D) journal bearings.

  55. The voltage of field system for an alternator is usually  (A) less than 200
V (B) between 200 V and 440 V (C) 400 V (D) more than 1 kV.

   56. When the number of slots / pole / phase is fractional, then this winding
is called  (A) short pitch winding. (B) full pitch winding. (C) fractional slot 
winding. (D) integral slot winding.    57. The electrical angle between the field
axis and axis of armature reaction of a loaded synchronous generator with armature
current lagging behind the excitation emf by ψ is  (A) ψ – 90 (B) ψ + 90 (C) 90 –
ψ (D) ψ + 180.

  58. Two synchronous generators G1and G2 are equally sharing the KVAR of the load
while operating in parallel. Keeping the terminal voltage fixed in order to shift
part of the KVAR load from G2 to G1  (A) The field current of G1 is lowered (B) 
The field current of G2 is raised (C) The field current of G1 is raised and of G2
lowered (D) The field current of G1 is lowered and of G2 is raised.

   [⌊Sample Job Interview Questions⌉](http://2.bp.blogspot.com/-1xVLZ1jJLNM/U-Tor9aMWCI/AAAAAAAABFA/cpgoKh51cMA/s100/Sample-Job-Interview-Questions.jpg)
59. A synchronous generator is operating with excitation adjusted for unity power
factor current at constant load. When on increasing the excitation the power factor(
A) will lag (B) will lead (C) will become zero (D) none of the above.

60. On changing the speed of an alternator from 4000 rpm to 2000 rpm, the generated
emf phase will become
  (A) 1/4 (B) 1/2 (C)1/3 (D)1/5

### Related posts:

No related posts.