DC MACHINE 7

 

DC MACHINES MCQ 7

1. A dc shunt generator driven at a normal speed in the normal direction fails to build up armature voltage because
a) the resistance of the armature is high
b) there is no residual magnetism
c) the field current is too small
d) none of these
ans. b

2. An ideal dc generator has a regulation of
a) 0%
b) 50%
c) 75%
d) 100%
ans. a

3. Which of the following statements is incorrect in dc shunt generators about hysteresis loss?
a) It can be minimized by laminating the armature
b) It is independent of lamination thickness
c) It depends upon the supply frequency
d) none of these
ans. a

4. Which of the following methods is most economical for finding the no-load losses of a large dc shunt motor?
a) Hopkinson's test
b) Swinburne's test
c) Retardation test
d) none of these
ans. b

5. The function of compensating windings placed in slots in the pole shoes is
a) to neutralize cross magnetizing effect
b) to neutralize the demagnetizing effect
c) to neutralize both the effects
d) to avoid flash over around the commutator
ans. d

6. In case of parallel operation of compound generators , for proper division of load from no load to full load , it is essential that
a) the regulation of each armature should be same
b) their series field resistances should be equal
c) their ratings should be identical
d) none of these
ans. a

7. The simplest way to shift load from one shunt generator to the other generator running in parallel is to
a) adjust their field rheostats.
b) use equalizer connection.
c) add resistance in their armature circuit
d) none of these.
ans. a

8. For parallel operation , the polarities of two generators
a) must oppose each other
b) must be same
c) may or may not be same
d) none of these
ans. a

9. The parts of the armature electric circuit which take active part in emf generation are
a) The coil sides inside the slots
b) the overhangs
c) both the coil sides inside the slots and the overhangs
d) the commutator segments
ans. a

10. The emf induced in the armature of a dc machine is
a) directly proportional to the flux and inversely proportional to the speed

b) directly proportional to both the flux and speed.
c) inversely proportional to both the flux and the speed.
d) none of the above
ans. b

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