Dc Genertors Objectives Part 04
61 . The condition for maximum efficiency in case of dc generator is Variable loss= Constant loss.
62 . A dc generator running at fixed speed and with fixed shunt field resistance has short circuit current is less than the maximum load current that it can feed.
63 . In a dc machine, the angle between the stator and rotor field is 90º.
64 . A dc shunt generator delivers 395 A at 250 V and the resistance of the shunt field and armature 50Ω and 0.05Ω respectively. The generated emf will be 270V.
65 . In a level compound generator, the terminal voltage at half full load is more than no load voltage.
66 . In a generator, the windage loss is proportional to square of armature speed.
67 . When field resistance of a dc shunt generator is increased beyond its critical value the generator will not build up.
68 . The number of armature parallel paths in a two-pole dc generator provided with duplex lap winding will be 4.
69 . When two shunt generators are operating in parallel, the easiest way to shift load from one generator to the other is to adjust their field rheostats.
70 . The number of armature parallel paths is 12 pole dc generator provided with triplex lap winding will be 36.
71 . In a dc generator the brushes are always placed along Magnetic neutral axis (MNA).
72 . If two generators are running in parallel and field of one of the generators is weakened too much, then it will run as a motor in same direction.
73 . In dc generators, the brushes remain in contact with conductors which lie in the interpolar gaps.
74 . Among the series and shunt generators, shunt generator has the better regulation.
75 . The armature reaction of an unsaturated dc machine is cross-magnetizing.
76 . A generator is said to be flat compounded when the voltage remains constant irrespective of the load on the generator.
77 . Iron losses in dc machine take place in armature rotor.
78 . Eddy current loss in a dc shunt generator occurs in magnetic as well as non-magnetic conductor material.
79 . A dc shunt generator remained inoperative for long time as a result of which residual magnetism was lost. The residual magnetism can be restored by connecting the shunt field to the battery.
80 . The change in speed of a dc generator due to increased loads is corrected by increasing input power of the prime mover.