## electrical

### Single Phase Induction Motor MCQ Questions and Answers Page - 3

1.
 The type of single-phase induction motor having the highest power factor at full load is A Shaded pole type B Split phase type C Capacitor start type capacitor run type D Capacitor run type Answer : D Explanation :
2.
 In various types of split phase 1- phase induction motors, the starting torques produced are in the following descending order A Capacitor split, resistor split, shaded pole B Capacitor split, shaded pole resistor split C Resistor split, capacitor-split, shaded pole D Shaded pole, resistor split, capacitor split Answer : A Explanation :
3.
 In hand tool applications, which one of the following single-phase motor is used? A Shaded pole motor B Capacitor start motor C Capacitor run motor D AC series motor Answer : D Explanation :
4.
 A dc shunt motor does not operate on ac due to A Low resistance of armature circuit B High resistance of field circuit C High inductance of field circuit D Reversal of polarity Answer : C Explanation :
5.
 A dc series motor is accidently connected to single phase ac supply. The torque produced will be A Of zero average value B Oscillating C Steady and unidirectional D Pulsating and unidirectional Answer : D Explanation :
6.
 A 230 V dc series motor is connected to a 230 V ac supply A The motor will vibrate violently B The motor will run with less efficiency and more sparking C The motor will into run D The fuse will be blown Answer : B Explanation :
7.
 If a dc series motor is operated on ac supply, it A Will not start at all B Will start and run but will have poor performance such as excessive sparking, poor efficiency and poor power factor C Will get damaged due to burning of its windings D Will run at excessively high speed. Answer : B Explanation :
8.
 AC series motors are built with as few fields turns as possible to reduce A Flux B Eddy current losses C Reactance D Speed Answer : C Explanation :
9.
 AC series motors in comparison to dc series motors do not have A Lesser number of fields turns B Larger number of armature conductors C Larger number of poles with lesser flux per pole D Wider air gap Answer : D Explanation :
10.
 AC series motors in comparison to dc series motors do not have A All parts of magnetic circuits laminated B Multi turn armature coils C Very short air gap D Single turn armature coils Answer : B Explanation :
11.
 In an ac series motor, power factor is improved by A Increasing the inductance of armature and field windings B Reducing the inductance of armature and field windings C Increasing the supply voltage D Both (a) and (c) Answer : B Explanation :
12.
 In an ac series motor, commutation is improved by A Reducing the number of armature conductors B Providing commutating poles C Providing commutating poles and shunting winding of each of these poles with a non-inductive resistance D Increasing field winding turns Answer : C Explanation :
13.
 In ac series motors armature coils are usually connected to commutator A Through resistors B Through inductors C Through capacitors D Solidly Answer : A Explanation :
14.
 A universal motor is one which has A Constant speed B Constant output C Capability of operating both on ac and dc with comparable performance D Maximum efficiency Answer : C Explanation :
15.
 A universal motor run at A Higher speed with dc supply and with less sparking B Higher speed with ac supply and with less sparking C Same speed with both ac and dc supplies D Higher speed with ac supply but with increased sparking at the brushes Answer : A Explanation :
16.
 Speed of the universal motor is A Dependent on frequency of supply B Proportional to frequency of supply C Independent of frequency of supply D None of the above Answer : C Explanation :
17.
 Direction of rotating of a universal motor can be reversed by A Interchanging the brush leads B Interchanging the supply terminals C Either (a) and (b) D None of these Answer : A Explanation :
18.
 The speed of a universal motor is usually reduced by using A V-belts B Gearing C Chains D Brakes Answer : B Explanation :
19.
 In a universal motor the most common cause(s) of brush sparking is/are A open armature winding B shorted armature winding C shorted field winding D all of the above Answer : D Explanation :
20.
 under no load operating condition, the speed of a universal motor is limited by A windage and friction B armature reaction C armature weight D supply frequency Answer : A Explanation :
21.
 The armature reaction in a large sized universal motor is neutralized by A Shifting the brushes B Connecting a compensating winding in series with the armature C Increasing the number of armature coils D Using low resistance brushes Answer : B Explanation :
22.
 In case of a high-speed universal motor____needs maximum attention A Air gap B End play C Balancing of rotor D Insulation of rotor Answer : C Explanation :
23.
 In universal motors, normally the ratio of width of brushes to the width of commutator segments is A 2:1 B 1:1 C 1:2 D 4:1 Answer : A Explanation :
24.
 Repulsion motor A Receives its armature current by induction B Is similar to a series motor except that rotor and stator windings are inductively coupled C Has high starting torque and high speed on no load D All of the above Answer : D Explanation :
25.
 A repulsion motor is equipped with A Slip rings B Centrifugal switch C Commutators and brushes D All of the above Answer : C Explanation :
26.
 In a repulsion motor A Stator usually carried a distributed winding similar to the main winding of an ordinary single-phase induction motor B The rotor or armature is similar to a dc motor armature with a drum type winding connected to the commutator C The brushes fixed directly opposite to each other are connected to each other or short circuited D All of the above Answer : D Explanation :
27.
 The commutation of repulsion motor is at its best A During starting B When runs near synchronous speed C When runs at 50% of synchronous speed D When run at 150% of synchronous speed Answer : B Explanation :
28.
 In a repulsion motor, commutator provides a means of connecting the A Stator windings B Armature windings C Starting winding D None of these Answer : B Explanation :
29.
 In a repulsion motor the brushes are connected A To the external supply B To each other short circuited C To the stator winding D None of the above Answer : B Explanation :
30.
 Starting winding of a single-phase motor of a refrigerator Is disconnected from the circuit by mean of a A Magnetic relay B Thermal relay C Centrifugal switch D None of the above Answer : A Explanation :
31.
 If a single-phase induction motor runs slower than normal, the most likely defect is A Worn bearing B Short-circuit in the winding C Open-circuit in the winding D None of the above Answer : A Explanation :
32.
 Which of the following motors is used in tape-recorders? A Hysteresis motor B Reluctance motor C Capacitor-run motor D Universal motor Answer : A Explanation :
33.
 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 reversal is required C It has low starting as well as rushing currents D It has high starting torque Answer : B Explanation :
34.
 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 starting as wells as running currents at relatively high-power factor D It is quite in operation Answer : C Explanation :
35.
 If the centrifugal switch of a two-value capacitor motor using two capacitor 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 Answer : D Explanation :
36.
 In a universal motor, the most common cause of brush sparking is A Open armature winding B Shorted armature winding C High commutator mica D All of the above Answer : D Explanation :
37.
 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 over heat D Run slower Answer : C Explanation :
38.
 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 or sleeve bearing Answer : D Explanation :
39.
 Which of the following statements regarding reluctance-start motor is incorrect? A It is similar to reluctance motor B It is basically an induction motor and not a synchronous one C So far as its basic working principle is connected, it is similar to shaded pole motor D The air-gap between rotor and salient poles is not uniform Answer : A Explanation :
40.
 To reverse the direction of rotation of a capacitor-start motor while it is running we should A Disconnect motor from the supply till it stops then reconnect it to supply with reversed connection of main or auxiliary winding B Disconnect motor from the supply and immediately reconnect it to supply with reversed connection of main or auxiliary winding C Reverse the direction of connection of the auxiliary winding and after motor comes to rest then connect auxiliary winding to the supply D Reverse the direction of connection of the auxiliary winding and immediately connect it to the supply Answer : A Explanation :
41.
 When a ceiling fan employing a capacitor run motor is switched on, it hums but does not burn. When it is driven by external means, it runs in whatever direction it is made to run. The trouble is due to A Blown fuse B Short in capacitor C An open in centrifugal switch D An open in capacitor Answer : D Explanation :
42.
 Which of the following motor has two separate windings on the motor? A Repulsion motor B Repulsion induction motor C Repulsion start induction run motor D None of the above Answer : B Explanation :
43.
 A shaded pole motor does not posses A Centrifugal switch B Capacitor C Commutator D All of the above Answer : D Explanation :
44.
 In a A.C series motor armature coils are usually connected to commutator A Through resistance B Through reactance C Through capacitor D Solidly Answer : A Explanation :
45.
 A universal motor is one of which A Can be operated either on D.C or A,C supply at approximately the same speed and output B Can be marketed internationality C Runs at dangerously high speed on no-load D None of the above Answer : A Explanation :
46.
 A repulsion motor is required with A Slip rings B commutator C both (a) and (b) D none of the above Answer : B Explanation :
47.
 The capacitor used in single-phase capacitor motor have no A voltage rating B di-electric medium C polarity marketing D definite value Answer : C Explanation :
48.
 if a D.C series motor is operated on A.C supply, it will A spark excessively B have poor efficiency C have poor power factor D all of the above Answer : D Explanation :
49.
 After the starting winding of a single-phase induction motor is disconnected from supply, it continues to run only on A running winding B field winding C rotor winding D compensating winding Answer : A Explanation :
50.
 A.C series motors as compared to D.C series motor has A Smaller brush width B Less number of field turns C Less air gap D All of the above Answer : D Explanation :
51.
 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 Answer : C Explanation :
52.
 Speed control of a universal motor is achieved by A Varying field flux with tapped field windings B Connecting rheostat in series C Applying variables voltage by means of variable auto-transformer D All of the above method Answer : D Explanation :
53.
 Hysteresis motor is particularly useful for high-quality record players and tape-recorders because A It revolves synchronously B It is not subject to any magnetic or mechanical vibration C It can be easily manufactured in extremely small sizes of upto 1 W output D It develops hysteresis torque which is extremely steady both in amplitude and phase Answer : D Explanation :
54.
 Which of the following statements regarding single-phase induction motor is correct? A It requires one winding B It can rotate in one direction only C It is self-starting D It is not self-starting Answer : D Explanation :
55.
 The starting winding of a single-phase motor is placed in A Armature B Field C Rotor D Stator Answer : D Explanation :
56.
 The speed of a universal motor is usually reduced by using A Gearing B Belts C Brakes D Chains Answer : A Explanation :