Single Phase Motor Questions Answers

81. For toys, the preferred motor is

(a) shaded-pole motor.
(b) capacitor motor.
(c) reluctance motor.
(d) universal motor. [A.M.I.E. Sec B. Elec. Machines Winter 2003]

82. Which of the following motors is suitable for timing and control purposes?

(a) Reluctance motor.
(b) Series motor.
(c) Repulsion motor.
(d) Hysteresis motor. [A.M.I.E. Sec B. Summer 2003]

83. In which single phase motor, the motor has no teeth or winding?

(a) Split-phase motor.
(b) Reluctance motor.
(c) Hysteresis motor.
(d) Universal motor.

85. If a single phase motor fails to start but gives humming noise, this may be due to

(a) low voltage.
(b) high voltage.
(c) shorted stator winding.
(d) blown fuses.

86. When a ceiling fan using a capacitor run motor is switched on, it hums but does not run. When it is driven by some external means it runs in the direction in which it was made to run. The probable cause is

(a) open-circuited capacitor.
(b) blown fuses.
(c) short-circuited capacitor.
(d) any of the above.

87. If a single phase induction motor runs at a speed lower than the rated one, the most likely defect is

(a) improper size fuses.
(b) wornout bearings or low voltage or overload.
(c) open-circuit in the winding.
(d) short-circuit in the winding.

88. An electric motor gets overheated. This may be due to

(a) overloading.
(b) shorted stator winding.
(c) worn-out or dry bearings.
(d) low or high voltage.
(e) any of the above.

89. If the centrifugal switch fails to open when the motor attains 70 to 80 per cent of synchronous speed, it would result in

(a) overloading of main winding.
(b) damage to centrifugal switch.
(c) overheating of auxiliary winding due to continuous flow of current and may get damaged.
(d) none of the above.

90. The running winding of a single phase motor is found earthed on testing. The most probable location of ground fault is at the

(a) end connection.
(b) end terminals.
(c) slot edge where coil enters or comes out of the slot.
(d) anywhere on the winding inside a slot.

91. Burning out of windings is due to,

(a) open-circuited capacitor.
(b) short-circuited capacitor.
(c) capacitor of improper rating.
(d) none of the above.

92. An open in the centrifugal switch circuit gives an indication of

(a) open winding.
(b) shorted winding.
(c) grounded winding.
(d) none of these.

93. Starting or auxiliary winding of a single phase motor used in a refrigerator is disconnected from the circuit by

(a) centrifugal switch.
(b) magnetic relay.
(c) thermal relay.
(d) any of the above.

94. Which of the following motors are used in largest number ?

(a) Fractional horse power motors.
(b) 3-phase induction motors.
(c) DC shunt motors.
(d) Synchronous motors.

95. Which of the following is not the induction motor ?

(a) Squirrel cage.
(b) Slip-ring.
(c) Reluctance.
(d) Double cage.

96. Which of the following types of motors are not the induction motors ?

(a) Repulsion motors.
(b) Split phase motors.
(c) Shaded pole motors.
(d) Repulsion start induction motors.

97. Which of the following types of motors are not the commutator motors ?

(a) AC series motors.
(b) Reluctance motors.
(c) Universal motors.
(d) Repulsion motors.
(e) Repulsion -induction motors.

98. Which of the following types of ac motors are synchronous type ?

(a) Reluctance motors.
(b) Hysteresis motors.
(c) Universal motors.
(d) both (a) and (b).

99. Which of the following motors does not use a centrifugal switch ?

(a) Shaded pole motor.
(b) Split phase motor.
(c) Capacitor-start capacitor run motor.
(d) Repulsion start induction motor.

100. Which single phase induction motor has the lowest speed ?

(a) Shaded pole.
(b) Universal.
(c) Hysteresis.
(d) Repulsion.