Objective questions and answers or MCQ of Electrical Machines page-11
176. The wide-open type slots in the design of stator of alternator will present the following disadvantage?
a) The size of the machine will increase
b) The size of the stator will increase
c) Air gap flux is distributed in the tufts and produce ripples in the wave of generated e.m.f.
d) None of the above
Ans: (c)
a) Salient pole type
b) None-salient pole type
c) (a) or (b)
d) None of the above
Ans: (b)
a) True
b) False
Ans: (b)
a) To prevent hunting only
b) To prevent hunting and provide the starting torque
c) To maintain proper synchronism
d) To provide the starting torque only
Ans: (b)
a) True
b) False
Ans: (b)
a) 3600 rpm
b) 3300 rpm
c) 3000 rpm
d) 1500 rpm
Ans: (c)
a) Short pitched coils in the alternators are used to reduce the size of the machines.
b) Short pitched coils are used to reduce the harmonics or to eliminate the harmonics from the generated e.m.f.
c) Short pitched coils are used to provide accurate phase difference of 120 degree to one phase to other.
d) Short pitched coils are used to reduce copper losses.
Ans: (b)
a) Total induced e.m.f. is increased
b) Total induced voltage is reduced
c) Total induced voltage is distorted
d) Total induced voltage is more and hence more insulation is required
Ans: (b)
a) (vector sum of induced e.m.fs. per coil)/(terminal voltage of the generator)
b) (arithmetic sum of induced e.m.fs. per coil)/(vector sum of induced e.m.fs. per coil)
c) (vector sum of induced e.m.fs. per coil)/(arithmetic sum of induced e.m.fs. per coil)
d) (arithmetic sum of induced e.m.fs. per coil)/(terminal voltage of the generator)
Ans: (c)
a) True
b) False
Ans: (b)
a) 0.96
b) 0.9
c) 0.933
d) 0.966
Ans: (d)
a) True
b) False
Ans: (a)
a) Demagnetizing
b) Cross-magnetizing
c) Square waveform
d) N phase with current
Ans: (b)
a) True
b) False
Ans: (a)
a) Load power factor is unity
b) Load power factor is zero lagging
c) Load power factor is zero leading
d) Load power factor is 7.0 lagging
Ans: (c)
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