Step-less speed control of induction motor is possible by which of the following methods?

A wound rotor induction motor is preferred, as compared to squirrel cage induction motor, when major consideration is

A

Slop speed operation

B

High starting torque

C

Low windage losses

D

All of the above

Which of the following methods is easily applicable to control the speed of the squirrel-cage induction motor?

A

By changing the number of stator poles

B

Rotor rheostat control

C

By operating two motors in cascade

D

By injecting e.m.f. in the rotor circuit

a motor -cycle covers 40 Km with a speed of 20 km /hr. Find the speed of the motor -cycle for the next 40 km journey so that the average speed of the whole journey will be 30 km / hr.

A

70.0km /hr

B

52.5km /hr

C

60.0km/hr

D

60. 5 km / hr

A motor cycle covers 40 km with a speed of 20 km/hr. Find the speed of the motor cycle for the next 40 km journy so that the average speed of the whole journey will be 30 km/hr?

A

70

B

52.5

C

60

D

60.5

The speed characteristics of an induction motor closely resemble the speed-load characteristics of which of the following machines

A

D.C. series motor

B

D.C. shunt motor

C

Universal motor

D

None of the above

While starting a synchronous motor by induction motor action, field winding is usually

A

connected to D.C. supply

B

short-circuited by low resistance

C

kept open-circuited

D

none of the above

A synchronous motor has better power factor as compared to that of an equivalent induction motor. This is mainly because

A

synchronous motor has no slip

B

stator supply is not required to produce magnetic field

C

mechanical load on the rotor remains constant

D

synchronous motor has large airgap

While starting a salient pole synchronous motor by induction motor action and connecting field discharge resistance across field, starting and accelerting torque is produced by

A

induction motor torque in field winding

B

induction motor torque in damper winding

C

eddy current and hysteresis torque in pole faces

D

reHetance motor torque due to saliency of the rotor

E

all of the above methods

Slip ring motor is preferred over squirrel cage induction motor where

A

High starting torque is required

B

Load torque is heavy

C

Heavy pull out torque is required

D

All of the above

The power factor of a synchronous motor is better than that of induction motor because

A

stator supply is relieved of responsibility of producing magnetic field

B

mechanical load on the motor can be adjusted

C

synchronous motor runs at synchronous speed

D

synchronous motor has large air gap

Step-less speed control of induction motor is possible by which of the following methods?

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