MCQ on single phase motor101-119

101. In a ceilingfan employing capacitor run motor

(a) secondary winding surrounds the primary winding✔
(b) primary winding surrounds the secondary winding
(c) both are usual arrangements
(d) none of the above

102. The shaded pole motor is used for
(a) high starting torque
(b) low starting torque✔
(c) medium starting torque
(d) very high starting torque

103. The rotor slots, in an induction motor, are usually not quite parallel to the shaft because it
(a) improves the efficiency
(b) helps the rotor teeth to remain under the stator teeth
(c) helps in reducing the tendency of the rotor teeth to remain under the stator teeth✔
(d) improves the power factor

104. The speed/load characteristics of a universal motor is same as that of
(a) A.C. motor
(b) D.C. shunt motor
(c) D.C. series motor✔
(d) none of the above

105. The purpose of stator winding in the compensated repulsion motor is to
(a) provide mechanical balance
(b) improve power factor and provide better speed regulation✔
(c) prevent hunting in the motor
(d) eliminate armature reaction

106. Which of the following motors is used for unity power factor ?
(a) Hysteresis motor
(b) Schrage motor✔
(c) Universal motor
(d) Reluctance motor

107. The motor used for the compressors is
(a) d.c. series motor
(b) shaded pole motor
(c) capacitor-start capacitor-run motor✔
(d) reluctance motor

108. Which of the following motors is used in a situation where load increases with speed ?
(a) Induction motor
(b) Three-phase series motor✔
(c) Schrage motor
(d) Hysteresis motor

109. In repulsion motor, zero torque is developed when
(a) brush axis is 45° electrical to field axis
(b) brush axis coincides with the field axis
(c) brush axis is 90° electrical to field axis
(d) both (b) and (c)✔

110. Centrifugal switch disconnects the auxiliary winding of the motor at about ____ percent of synchronous speed
(a) 30 to 40
(b) 70 to 80✔
(c) 80 to 90
(d) 100

111. Starting winding of a single phase motor of a refrigerator is disconnected from the circuit by means of a
(a) magnetic relay✔
(b) thermal relay
(c) centrifugal switch
(d) none of the above

112. If a single phase induction motor runs slower than normal, the most likely defect is
(a) worn bearings✔
(b) short-circuit in the winding
(c) open-circuit in the winding
(d) none of the above

113. Which of the following motors is used in tape-recorders ?
(a) Hysteresis motor✔
(b) Reluctance motor
(c) Capacitor-run motor
(d) Universal motor

114. Which of the following statements regarding two value capacitor motor is incorrect ?
(a) It is a reversing motor
(b) It is preferred to permanent-split single-value capacitor motor where frequent reversals are required✔
(c) It has low starting as well as rushing currents
(d) It has high starting torque

115. Two-value capacitor motor finds increased application as compressor motor in small home air-conditioners
because
(a) it is comparatively cheaper
(b) it has almost non-destructible capacitor
(c) it has low starting as well as running currents at relatively high power factor✔
(d) it is quiet in operation

116. If the centrifugal switch of a two-value capacitor motor using two capacitors fails to open then
(a) motor will not come up to speed
(b) motor will not carry the load
(c) current drawn by the motor will be excessively high
(d) electrolytic capacitor will, in all probability, suffer break down✔

117. In a universal motor, the most common cause of brush sparking is
(a) open armature winding
(b) shorted armature winding
(c) shorted field winding”
(d) high commutator mica
(e) all of the above✔

118. If starting winding of a single-phase induction motor is left in the circuit, it will
(a) run faster
(b) spark at light loads
(c) draw excessive current and overheat✔
(d) run slower

119. Most of the fractional horsepower motors have either
(a) hard and annealed bearings
(b) ball or roller bearings
(c) soft and porous bearing
(d) plain and sleeve bearing✔