Electrical Engineering Questions - 6
Electrical Machine
Single Phase Motor
1. After the starting winding of a single phase induction motor is disconnected from supply, it continues to run only on
(a) running winding
(b) rotor winding
(c) field winding
(d) compensating winding
Ans: a
2. Which of the following statements regarding repulsion-start induction motor is incorrect ?
(a) It requires more maintenance of commutator and other mechanical devices
(b) It makes quite a bit of noise on starting
(c) In fractional horse power motors, it has replaced the capacitor motors
(d) It is not easily reversed
Ans: c
3. A.C. series motor as compared to D.C. series motor has
(a) smaller brush width
(b) less number of field turns
(c) more number of armature turns
(d) less air gap
(e) all of the above
Ans: e
4. Locked rotor current of a shaded pole motor is
(a) equal to full load current
(b) less than full load current
(c) slightly more than full load current
(d) several times the full load current
Ans: c
5. Speed control of a universal motor is achieved by
(a) varying field flux with tapped field winding's
(b) connecting rheostat in series
(c) applying variable voltage by means of silicon controlled rectifier
(d) applying variable voltage by means of variable auto-transformer
(e) all of the above methods
Ans: e
6. Hysteresis motor is particularly useful for high-quality record players andtape-recorders because
(a) it revolves synchronously
(b) it is not subject to any magnetic or mechanical vibrations
(c) it can be easily manufactured in extremely small sizes of up to 1 W output
(d) it develops hysteresis torque which is extremely steady both in amplitude and
phase
Ans: d
7. Which of the following statements regarding hysteresis motor is in incorrect ?
(a) It is extremely sensitive to fluctuations in supply voltage
(b) Its high starting torque is due to its high rotor hysteresis loss
(c) It is extremely quiet in operation
(d) It accelerates from rest to full-speed almost instantaneously
Ans: a
8. Which of the following statements regarding single-phase induction motoristcorrect ?
(a) It requires only one winding
(b) It can rotate in one direction only
(c) It is self-starting
(d) It is not self-starting
Ans: d
9. The starting winding of a single-phase motor is placed in
(a) armature
(b) field
(c) rotor
(d) stat-or
Ans: d
10. The speed of a universal motor is usually reduced by using
(a) gearing
(b) belts
(c) brakes
(d) chains
Ans: a
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