MULTIPLE CHOICE QUESTIONS
Q.1 A d.c. shunt motor runs at no load speed of
1140 r.p.m. At full load, armature reaction weakens the
main flux by 5% whereas the armature circuit voltage drops by 10%. The motor full
load speed in r.p.m. is
(A)
1080
(B) 1203
(C) 1000
(D) 1200
Q.2 The introduction of interpoles in between the
main pole improves the performance of
d.c.
machines, because
(A) The interpole produces additional flux to
augment the developed torque.
(B) The flux waveform is improved with reduction
in harmonics.
(C) The inequality of air flux on the top and
bottom halves of armature is removed.
(D) A counter e.m.f. is induced in the coil
undergoing commutation.
Q.3 The rotor power output of a 3-phase induction
motor is 15 KW and corresponding slip
is 4%. The
rotor copper loss will be
(A) 600 W.
(B) 625 W
(C)
650 W
(D) 700 W
Q.4 The direction of rotation of hysteresis motor
is reversed by
(A)
Shift shaded pole with respect to main pole
(B)
Reversing supply lead
(C)
Either A or B
(D)
Neither A nor B
Q.5 A
1.8°step, 4-phase stepper
motor has a
total of 40 teeth on 8 pole
of stator. The number of rotor teeth for their rotor
will be
(A)
40
(B) 50
(C)
100
(D) 80
Q.6 In DC generators, armature reaction is produced actually by
(A)
Its field current.
(B) Armature conductors.
(C)
Field pole winding.
(D) Load current in armature.
Q.7 Two transformers operating in parallel will
share the load depending upon their
(A)
Rating.
(B) Leakage reactance.
(C) Efficiency.
(D)
Per-unit impedance.
Q.8 As compared to shunt and compound DC motors,
the series DC motor will have the
highest
torque because of its comparatively ____________ at the start.
(A)
Lower armature resistance.
(B) Stronger series field.
(C)
Fewer series turns.
(D) Larger armature current.
Q.9 A
400kW, 3-phase, 440V,
50Hz induction motor
has a speed
of 950 r.p.m.
on full-load. The machine has 6
poles. The slip of the machine will be _______________.
(A)
0.06
(B) 0.10
(C)
0.04
(D) 0.05
Q.10 Reduction in the capacitance of a
capacitor-start motor, results in reduced
(A)
Noise.
(B) Speed.
(C)
Starting torque.
(D) Armature reaction.
