Single Phase Induction Motor MCQ

41. A capacitor selected for capacitor-start induction motor should be rated for

(a) peak voltage.
(b) rms voltage.
(c) average voltage.
(d) none of these.

42. The capacitor employed in a capacitor-start induction motor has no

(a) voltage rating.
(b) polarity marking.
(c) dielectric rating.
(d) definite capacitance value.

43. The value of capacitor for a capacitor-start induction motor is determined by its

(a) speed.
(b) efficiency.
(c) starting torque.
(d) power factor.

44. The phase-split in a capacitor-start induction motor can be adjusted to approximately 90° by

(a) selecting capacitor employed in the auxiliary winding of correct value.
(b) adjusting the reactance of the main winding.
(c) adjusting the supply voltage.
(d) choosing correct number of turns of the auxiliary winding.

45. Which one of the following capacitor-start split-phase motor will have the largest value of capacitance ?

(a) 1/2 hp; 3,450 rpm.
(b) 1/4 hp; 1,725 rpm.
(c) 1/2 hp; 1,140 rpm.
(d) 3/4 hp; 1,140 rpm. [U.P.S.C. I.E.S. 1993]

46. A capacitor-start single phase induction motor is used for

(a) easy to start loads.
(b) medium start loads.
(c) hard to start loads.
(d) any type of start loads. [U.P.S.C. I.E.S. 2005]

47. The capacitor start motor like resistance start motor, has the auxiliary winding disconnected by means of a centrifugal switch as the motor picks up speed. This is necessary because

(a) the capacitance that gives the largest starting torque is about four times too big for the best running conditions.
(b) if the capacitor is used only for starting, it can be electrolytic type which is much smaller and cheaper than the paper capacitor required for continuous operation.
(c) both (a) and (b).
(d) none of these.

48. In comparison to a resistance start motor, the capacitor start motor has

(a) high starting torque (about double).
(b) low starting current (about half).
(c) high running torque.
(d) larger phase difference between two winding currents.
(e) more number of turns on auxiliary winding.
(f) all of the above statements except (c) are correct.

49. A capacitor start induction motor is switched on to supply with its capacitor replaced by an inductor of equivalent reactance. The motor will

(a) not start at all.
(b) start and run slowly.
(c) start and run at rated speed.
(d) start with humming noise.

50. If the capacitor of a capacitor start induction motor is short circuited, the motor will

(a) start.
(b) not start.
(c) burn.
(d) start with jerks.

51. If the capacitor of a capacitor start induction motor fails to open when it picks up the speed,

(a) the motor will stop.
(b) the auxiliary winding will get damaged.
(c) the capacitor will get damaged.
(d) the main winding will get damaged.

52. Capacitor-start capacitor-run induction motor is basically a ……. motor.

(a) two phase
(b) ac series
(c) commutator
(d) synchronous

53. In a capacitor-start capacitor-run induction motor

(a) oil impregnated paper of small value and continuous rating is connected in series with the main winding.
(b) larger value electrolytic short duty capacitor is connected in series with auxiliary winding through a centrifugal switch.
(c) low value oil impregnated paper capacitor is connected in series with the auxiliary winding through a centrifugal switch.
(d) both (a) and (b).

54. In a capacitor-start capacitor-run single phase induction motor, the value of capacitor connected in series with starting winding is approximately …….. times that of capacitor connected in the main or running winding.

(a) 1/3
(b) 3
(c) 1/2
(d) twice

55. In a capacitor-start and run 1-phase induction motor, starting capacitor C1 and permanent capacitor C2, are as under:

(a) C1 : electrolytic type; C2 : paper type.
(b) C1 : electrolytic type; C2 : mica type.
(c) C1 : mica type; C2 : electrolytic type.
(d) C1 : paper type; C2 : electrolytic type. [A.M.1.E. Sec B. Winter 2003]

56. Which one of the following statements regarding a capacitor-start, capacitor-run single phase induction motor is correct?

(a) One of the capacitors is in the circuit during starting and both are in the circuit during running.
(b) Both the capacitors are in the circuit during starting and one of them in the circuit during running.
(c) Both the capacitors are in the circuit during starting and running.
(d) One of the capacitor is in the circuit during starting and other is in the circuit during running.

57. As compared to capacitor start motors two capacitor type induction motors have

(a) better power factor and better efficiency.
(b) constant torque and so quite operation.
(c) greater overload capacity.
(d) high starting torque
(e) all of the above.

58. Two capacitor type induction motors have the main drawback of

(a) high cost.
(b) low power factor.
(c) pulsating torque.
(d) poor starting torque.

59. Two capacitor type single phase induction motor is generally coupled with the air-conditioner compressor because it

(a) is cheaper.
(b) is quite in operation.
(c) has higher running torque.
(d) has low starting as well as running currents.

60. In a ceiling fan employing permanent capacitor 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.