Polyphase Induction Motors — Part 2 MCQs with Explanations

Power factor at starting is low as compared to that while running is the correct answer to “In a three-phase induction motor”. This question is standard in competitive examination syllabi for Polyphase Induction Motors.

Rotor current is the correct answer to “In the circle diagram for induction motor, the diameter of the circle represents”. This question is standard in competitive examination syllabi for Polyphase Induction Motors.

Slip times the stand still e.m.f. induced in the rotor is the correct answer to “In a squirrel cage motor the induced e.m.f. is”. This question is standard in competitive examination syllabi for Polyphase Induction Motors.

Smaller is the correct answer to “Size of a high speed motor as compared to low speed motor for the same H.P. will be”. This question is standard in competitive examination syllabi for Polyphase Induction Motors.

To short circuit the rotor at slip rings is the correct answer to “The purpose of using short-circuit gear is”. This question is standard in competitive examination syllabi for Polyphase Induction Motors.

Reduces starting torque as well as maximum torque is the correct answer to “Insertion of reactance in the rotor circuit”. This question is standard in competitive examination syllabi for Polyphase Induction Motors.

All of the above is the correct answer to “The maximum torque in an induction motor depends on”. This question is standard in competitive examination syllabi for Polyphase Induction Motors.

Carbon steel is the correct answer to “The shaft of an induction motor is made of”. This question is standard in competitive examination syllabi for Polyphase Induction Motors.

None is the correct answer to “The number of slip rings on a squirrel cage induction motor is usually”. This question is standard in competitive examination syllabi for Polyphase Induction Motors.

Higher starting torque is the main consideration is the correct answer to “A squirrel cage induction motor is not selected when”. This question is standard in competitive examination syllabi for Polyphase Induction Motors.

All above features are required is the correct answer to “Slip ring motor is recommended where”. This question is standard in competitive examination syllabi for Polyphase Induction Motors.

In the same direction as the direction of the field is the correct answer to “If a 3-phase supply is given to the stator and rotor is short circuited rotor will move”. This question is standard in competitive examination syllabi for Polyphase Induction Motors.

Grease is the correct answer to “Lubricant used for ball bearing is usually”. This question is standard in competitive examination syllabi for Polyphase Induction Motors.

Slip-ring induction motor is the correct answer to “For which motor the speed can be controlled from rotor side”. This question is standard in competitive examination syllabi for Polyphase Induction Motors.

730 r.p.m. is the correct answer to “5 H.P., 50Hz, 3-phase, 440 V, induction motors are available for the following r.p.m. Which motor will be the costliest”. This question is standard in competitive examination syllabi for Polyphase Induction Motors.

To reduce the magnetic hum and locking tendency of the rotor is the correct answer to “In the squirrel-cage induction motor the rotor slots are usually given slight skew”. This question is standard in competitive examination syllabi for Polyphase Induction Motors.

All above methods is the correct answer to “Temperature of the stator winding of a three phase induction motor is obtained by”. This question is standard in competitive examination syllabi for Polyphase Induction Motors.

Directly proportional to slip is the correct answer to “In case of the induction motors the torque is”. This question is standard in competitive examination syllabi for Polyphase Induction Motors.

Self-starting with low torque is the correct answer to “An induction motor is”. This question is standard in competitive examination syllabi for Polyphase Induction Motors.

Directly proportional to slip is the correct answer to “The torque of an induction motor is”. This question is standard in competitive examination syllabi for Polyphase Induction Motors.

Harmonics developed in the motor is the correct answer to “The 'crawling' in an induction motor is caused by”. This question is standard in competitive examination syllabi for Polyphase Induction Motors.

Harmonics developed in the motor is the correct answer to “The crawling in the induction motor is caused by”. This question is standard in competitive examination syllabi for Polyphase Induction Motors.

The power factor will decrease is the correct answer to “In case the air gap in an induction motor is increased”. This question is standard in competitive examination syllabi for Polyphase Induction Motors.

Slip ring type is the correct answer to “For driving high inertia loads best type of induction motor suggested is”. This question is standard in competitive examination syllabi for Polyphase Induction Motors.

e.m.f. is injected in the rotor circuit is the correct answer to “An induction motor can run at synchronous speed when”. This question is standard in competitive examination syllabi for Polyphase Induction Motors.

High starting torque is required is the correct answer to “Slip ring motor is preferred over squirrel cage induction motor where”. This question is standard in competitive examination syllabi for Polyphase Induction Motors.

16% in the rotor torque is the correct answer to “A change of 4% of supply voltage to an induction motor will produce a change of approximately”. This question is standard in competitive examination syllabi for Polyphase Induction Motors.

Crawling is the correct answer to “If an induction motor with certain ratio of rotor to stator slots, runs at $$\frac{1}{7}$$ of the normal speed, the phenomenon will be termed as”. This question is standard in competitive examination syllabi for Polyphase Induction Motors.

Having number of rotor slots more or less than the number of stator slots (not equal) is the correct answer to “The 'cogging' of an induction motor can be avoided by”. This question is standard in competitive examination syllabi for Polyphase Induction Motors.

Short-circuit test only is the correct answer to “The power scale of circle diagram of an induction motor can be found from”. This question is standard in competitive examination syllabi for Polyphase Induction Motors.

Equal to number of poles in stator is the correct answer to “In a three-phase induction motor, the number of poles in the rotor winding is always”. This question is standard in competitive examination syllabi for Polyphase Induction Motors.

Ball bearings is the correct answer to “Which type of bearing is provided in small induction motors to support the rotor shaft”. This question is standard in competitive examination syllabi for Polyphase Induction Motors.

Short-circuit test only is the correct answer to “The vafcie of transformation ratio of an induction motor can be found by”. This question is standard in competitive examination syllabi for Polyphase Induction Motors.

Asynchronous motor is the correct answer to “An induction motor is identical to”. This question is standard in competitive examination syllabi for Polyphase Induction Motors.

All of the above is the correct answer to “The complete circle diagram of induction motor can be drawn with the help of data found from”. This question is standard in competitive examination syllabi for Polyphase Induction Motors.

6 poles is the correct answer to “An induction motor with 1000 r.p.m. speed will have”. This question is standard in competitive examination syllabi for Polyphase Induction Motors.

Squirrel cage induction motor is the correct answer to “Less maintenance troubles are experienced in case of”. This question is standard in competitive examination syllabi for Polyphase Induction Motors.

Its power factor goes on increasing up to full load and then it falls again is the correct answer to “As load on an induction motor goes on increasing”. This question is standard in competitive examination syllabi for Polyphase Induction Motors.

Cast iron is the correct answer to “The frame of an induction motor is usually made of”. This question is standard in competitive examination syllabi for Polyphase Induction Motors.

Low horsepower motors is the correct answer to “DOL starting of induction motors is usually restricted to”. This question is standard in competitive examination syllabi for Polyphase Induction Motors.