 ## electrical

### Single Phase Induction Motor MCQ Questions and Answers Page - 2

1.
 The  direction of rotation of a shade pole induction motor A Cannot be reversed unless there is a provision for shifting of shading coil from one half to the B Can be reversed by interchanging C Can be reversed by interchanging the supply terminals D Can be reversed by open circuiting the shading rings Answer : Select Correct Ans Explanation :
2.
 The capacitor employed in a capacitor start induction motor has no A Voltage rating B Polarity marking C Dielectric rating D definite capacitance value Answer : Select Correct Ans Explanation :
3.
 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 Answer : Select Correct Ans Explanation :
4.
 The capacitor usually used on 1440 rpm, 50Hz capacitor start induction motor is of electrolytic type and ____capacity A 10 µF B 100 µF C 350 µF D 800 µF Answer : Select Correct Ans Explanation :
5.
 The value of capacitor for a capacitor start induction motor can be adjusted to approximately 900 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 . Answer : Select Correct Ans Explanation :
6.
 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 Answer : Select Correct Ans Explanation :
7.
 A capacitor start induction motor is switched on to supply with its capacitor replaced by a 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 Answer : Select Correct Ans Explanation :
8.
 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 Answer : Select Correct Ans Explanation :
9.
 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 Answer : Select Correct Ans Explanation :
10.
 Capacitor start capacitor  run induction motor is basically a ____motor A Two phase B Ac series C Commutator D Synchronous Answer : Select Correct Ans Explanation :
11.
 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 Answer : Select Correct Ans Explanation :
12.
 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 Answer : Select Correct Ans Explanation :
13.
 Capacitor start and capacitor run motors are used in A Hoists B Rolling mills C Mining D Refrigerator Answer : Select Correct Ans Explanation :
14.
 In a shaded pole motor the phase splitting is achieved by placing a shagging coil at the slot cut around the A Larger part of the pole B Smaller part of the pole C Both the parts of the pole D Any of the above Answer : Select Correct Ans Explanation :
15.
 In a shaded pole motor the rotating field is developed by using A Salient poles B A capacitor C Shading coils D Damper winding Answer : Select Correct Ans Explanation :
16.
 Shaded pole motor is proved with A Laminated salient poles and a squirrel cage rotor B A commutator C A capacitor D A centrifugal switch Answer : Select Correct Ans Explanation :
17.
 In a shaded pole motor, shading coils are used to A reduce winding losses B reduce friction losses C produce rotating magnetic field D protect against sparking Answer : Select Correct Ans Explanation :
18.
 in a shaded pole induction motor, locked rotor current is ____full load current A less than B equal to C slightly more than D several times the Answer : Select Correct Ans Explanation :
19.
 The speed of single phase induction motors can be controlled by A Varying the applied voltage to the stator winding B Varying the number of poles on the stator C Either (a) or (b) D None of the above Answer : Select Correct Ans Explanation :
20.
 The wattage rating for a ceiling motor will be in the range A 50 to 250 W B 250 to 500w C 50 to 150 W D 10 to 20 W Answer : Select Correct Ans Explanation :
21.
 In a two-value capacitor motor, the capacitor used for running purpose is A Air capacitor B Paper spaced oil-filled type C Ceramic type D AC electrolytic type Answer : B Explanation :
22.
 Which of the following motors can be run on A.C as well as D.C supply? A Universal motor B Repulsion motor C Synchronous motor D Reluctance motor Answer : A Explanation :
23.
 In A.C series motor compensating winding is employed to A Reduce the effects of armature reaction B Increase the torque C Reduce sparking at the brushes D None of the above Answer : C Explanation :
24.
 Which of the following single-phase induction motor is generally used in time phonographs? A Resistance start B Capacitor start capacitor run C Shaded pole D Universal Answer : C Explanation :
25.
 Which of the following motors has highest starting torque? A Repulsion motor B Shaped pole motor C Capacitor-start motor D Split-phase motor Answer : C Explanation :
26.
 The repulsion start induction run motor is used because of A Good power factor B High efficiency C Minimum cost D High starting torque Answer : D Explanation :
27.
 In case of a shaded pole motor the direction of rotation of motor is A From main pole to shaded pole B From shaded pole to main pole C Either of the above depending on voltage D Either of the above depending on power factor Answer : A Explanation :
28.
 In case of high-speed universal motor which of the following needs more attention? A End play B Air gap C Insulation in rotor D Balancing of rotor Answer : D Explanation :
29.
 The wattage of motor for driving domestic sewing machine will be around? A 100 to 150 W B 40 to 75 W C 10 to 30 W D 5 to 10 W Answer : A Explanation :
30.
 Which of the following single-phase motors has relatively poor starting torque? A Universal motor B Repulsion motor C Capacitor motor D All single-phase motor has zero starting torque Answer : C Explanation :
31.
 Which type of load is offered by cranes and hoists? A Gradually varying load B Non-reversing, no-load start C Reversing, light start D Reversing, heavy start Answer : D Explanation :
32.
 The speed of a general motor is generally reduced by using A Gear trains B V-belts C Brakes D Chains Answer : A Explanation :
33.
 Which of the following motors can be used for unity power factor? A Capacitor run motor B Shaded pole motor C Hysteresis motor D Schrage motor Answer : D Explanation :
34.
 When a D.C series motor is connected to A.C supply, the power factor will be low because of A High inductance of field and armature circuit B Induced current in rotor due to variation of flux C Fine copper wire winding D None of the above Answer : A Explanation :
35.
 The direction of rotation of universal motor can be reversed. Then by reversing the flow of the current through A Armature winding B Field winding C Either armature winding or field winding D None of the above Answer : C Explanation :
36.
 In which single-phase motor, the rotor has no teeth or winding? A Split phase motor B Reluctance motor C Hysteresis motor D Universal motor Answer : C Explanation :
37.
 Which motor is normally free from mechanical and, magnetic vibration? A Split phase motor B Universal motor C Hysteresis motor D Shaded pole motor Answer : C Explanation :
38.
 As hysteresis motor are free from mechanical and magnetic vibration therefore these are considered as suitable for A Fans B Blowers C Sound equipment D Mixer grinders Answer : C Explanation :
39.
 A reluctance motors A Is self-starting B Is constant speed motor C Needs no D.C excitation D All of the above Answer : D Explanation :
40.
 In a hysteresis motor, the rotor must have A Retentively B Resistivity C Susceptibility D None of the above Answer : A Explanation :
41.
 The rotor of a hysteresis motor is made of A Aluminium B Cast iron C Chrome steel D Copper Answer : C Explanation :
42.
 The electric motor used in portable drills is A Capacitor run motor B Hysteresis motor C Universal motor D Repulsion motor Answer : C Explanation :
43.
 Which of the following applications always have some load whenever switched on? A Vacuum cleaner B Fan motor C Pistol drills D All of the above Answer : C Explanation :
44.
 The speed control of universal motor used for sewing machines is by A Friction B Varying the resistance C Tapping the field D Centrifugal mechanism Answer : B Explanation :
45.
 Torque developed by a single-phase induction motor at starting is A Pulsating B Uniform C None of the above D Nil Answer : D Explanation :
46.
 In split phase motor a min winding is of A Thin wire placed at the top of the slots B Thin wire placed at the bottom of the slots C Thick wire placed at the bottom of the slots D Thick wire placed at the top of the slots Answer : C Explanation :
47.
 In repulsion motor, maximum torque is developed when A Brush axis is at 45° electrical to the field axis B Brush axis coincide with the field axis C Brush axis is at 90° electrical to the field axis D None of the above Answer : A Explanation :
48.
 If the centrifugal switch does not open at 70 to 80 % of synchronous speed of the motor, it would result in A Damage to the starting winding B Damage to the centrifugal switch C Overloading of running winding D None of the above Answer : A Explanation :
49.
 Speed torque characteristics of a repulsion induction motor is similar to that of a D.C A Shunt motor B Series motor C Compound motor D Separately excited motor Answer : C Explanation :
50.
 In a ceiling fan employing capacitor run motor A Secondary winding surrounds the primary winding B Primary windings surround the secondary winding C Both are usual arrangements D None of the above Answer : A Explanation :
51.
 The shaded pole motor is used for A High staring torque B Low starting torque C Medium starting torque D Very high starting torque Answer : B Explanation :
52.
 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 Answer : C Explanation :
53.
 The speed/loads 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 Answer : C Explanation :
54.
 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 Eliminates armature reaction Answer : B Explanation :
55.
 The motor used for the compressor is A D.C series motor B Shaded pole motor C Capacitor-start capacitor-run motor D Reluctance motor Answer : C Explanation :
56.
 Which of the following motor is used in a situation where load increases will speed? A Induction motor B Three-phase series motor C Schrage motor D Hysteresis motor Answer : B Explanation :
57.
 In repulsion motor, zero torque is developed when A Brush axis is 45° electrical to field axis B Brush axis coincide with the field axis C Brush axis is 90° electrical to field axis D Both (b) and (c) Answer : D Explanation :
58.
 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 Answer : B Explanation :