KSEB Sub-Engineer Old Question Paper

KSEB Sub-Engineer Question Paper

1. The rotor of a salient pole alternator consist of ....

ANS: shaft, spider, yoke and salient poles

2. What are the methods of excitation of alternators?

ANS: Self-excited dc shut generator mounted on the extended shaft of the alternators.

3. Within first few cycles after the occurance of the short circuit on alternator, the current will be ...

ANS: ten to twelve times the full load current.

4. Turbo alternators usually have.....

ANS: 2 Poles

5. Salient pole type of rotor construction is usually provided in alternators used in .....

ANS: hydro power stations

6. Alternator of a central power station will have .....

ANS: revolving field winding

7. Where the terminal voltage of an alternator falls on throwing of the load, it indicates.....

ANS: that the load is capacitive

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8. In order that two alternators should run in parallel......

ANS: their speed should be in direct ratio of their number of poles.

9.Parallel operation of two synchronous alternators will be better achieved....

ANS: if both machines have less resistance than synchronous reactance.

10. Modern synchronous are designed to have high value of leakage reactance and armature reaction. This is done..

ANS: to reduce mechanical and electrical damage in the case of accidental short circuits.

11.Short circuit current of an alternator is limited by.....

ANS:the saturated synchronous impedance

12. Alternators are now a days designed to have poor regulation because....

ANS: it limits the value of short circuit current

13. Alternators in aircraft have operating frequency of ....

ANS: 400Hz

14.Frequency of 400Hz is used in air craft alternators to ....

ANS:reduce the weight of the alternators

15. Modern 3Q alternator of central power station will have generated voltage of ....

ANS: 11000 V

16. When a 3Q alternator supplies reactive load, armature reaction flux will be ....

ANS: along the axis of the field

17. When a 3Q alternator supplies incluctive load, armature reaction flux will be ....

ANS: opposing the main magnetic field

18.When a 3Q alternator supplies resistive load, armature reaction flux will be ....

ANS: at 90 degree with the field axis

19. Dampers in large generator

ANS: increase stability

20. Short-pitched coils in the alternator are used ....

ANS: to reduce the harmonics from the generated emf of the alternator