1. At unity load power factor, the effect of armature reaction on the main-field flux of an alternator is
(a) nominal.
(b) demagnetizing.
(c) magnetising.
(d) distortional.
Answer ⇓
2. For proper parallel operation, 3-phase alternators must have the same
(a) speed.
(b) voltage rating.
(c) kVA rating.
(d) excitation.
Answer ⇓
3. Zero power factor method of an alternator is used to find its
(a) efficiency.
(b) voltage regulation.
(c) armature resistance.
(d) synchronous impedance.
Answer ⇓
4. If a stationary alternator is connected to a live bus bar-bar it will
(a) decrease the bus bar voltage.
(b) get short-circuited.
(c) run as synchronous motor.
(d) nothing happen.
Answer ⇓
5. If the number of poles of an alternator is increased, the generated emf
(a) decreases.
(b) increases.
(c) remain same.
(d) slightly decreases.
Answer ⇓
6. If the speed of an alternator is reduced by half, its generated emf will become
(a) double.
(b) same.
(c) half.
(d) one fourth.
Answer ⇓
7. At leading p.f., the armature flux in an alternator ……. the rotor flux.
(a) opposes.
(b) aids.
(c) distorts.
(d) does not affect.
Answer ⇓
8. At lagging loads, armature reaction in an alternator is
(a) cross-magnetising
(b) demagnetising.
(c) magnetising.
(d) all of the above.
Answer ⇓
9. The power factor on which an alternator operates depends on the
(a) speed of the prime mover.
(b) nature of the load being supplied.
(c) armature losses.
(d) copper losses.
Answer ⇓
10. High speed alternators are driven by
(a) steam turbines.
(b) hydraulic turbines.
(c) wind turbines.
(d) steam turbines.
Answer ⇓
11. Low speed alternators are driven by
(a) hydraulic turbines.
(b) steam turbines.
(c) wind turbines.
(d) diesel engines.
Answer ⇓
12. Which of the following method is used for the cooling of large turbo alternators ?
(a) air cooling.
(b) hydrogen cooling.
(c) oil cooling.
(d) water cooling.
Answer ⇓
13. High capacity generators are usually
(a) air cooled.
(b) oil cooled.
(c) SF6 cooled.
(d) hydrogen cooled.
Answer ⇓
14. During hydrogen cooling of generator, the windage losses are
(a) increased.
(b) reduced.
(c) remain same.
(d) maximum.
Answer ⇓
15. Which of the following method can be used to determined the voltage regulation of an alternoator?
(a) short circuted test.
(b) open circuited test.
(c) block rotor test.
(d) synchronous impedance method.