Deck 9: Motors and Drives for Industrial Applications

Question 1

A wound rotor induction motor is preferred over squirrel cage induction motor when the major consideration involved is

A)high starting torque
B)low starting current
C)speed control over limited range
D)all of the above.

Answer 1

all of the above.

Question 2

When smooth and precise speed control over a wide range is desired, the motor preferred is

A)synchronous motor
B)squirrel cage induction motor
C)wound rotor induction motor
D)dc motor.

Answer 2

dc motor.

Question 3

When quick speed reversal is a consideration, the motor preferred is

A)synchronous motor
B)squirrel cage induction motor
C)wound rotor induction motor
D)dc motor.

Answer 3

dc motor.

Question 4

Stator voltage control for speed control of induction motors is suitable for

A)fan and pump drives
B)drive of a crane
C)running it as generator
D)constant load drive.

Question 5

The selection of control gear for a particular application is based on the consideration of

A)duty
B)starting torque
C)limitations on starting current
D)all of the above.

Question 6

As compared to squirrel cage induction motor, a wound rotor induction motor is preferred when the major consideration is

A)high starting torque
B)low windage losses
C)slow speed operation
D)all of the above.

Question 7

A synchronous motor is found to be more economical when the load is above

A)1 kW
B)10 kW
C)20 kW
D)100kW.

Question 8

The advantage of a synchronous motor in addition to its constant speed is

A)high power factor
B)better efficiency
C)lower cost
D)all of the above.

Question 9

In motor circuit static frequency changers are used for

A)power factor improvement
B)improved cooling
C)reversal of direction
D)speed regulation.

Question 10

In case of traveling cranes, the motor preferred for boom hoist is

A)AC slip ring motor
B)Ward Leonard controlled DC shunt motor
C)Synchronous motor
D)Single phase motor.

Question 11

The characteristics of drive for. crane hoisting and lowering is

A)smooth movement
B)precise control
C)fast speed control
D)all of the above.

Question 12

The capacity of a crane is expressed in terms of

A)Span
B)Type of drive
C)Tonnes

Question 13

The traveling speed of cranes varies from

A)1 to 2.5 m/s
B)5 to 15 m/s
C)20 to 22.5 m/s
D)25 to 40 m/s.

Question 14

In overhead traveling cranes

A)continuous duty motors are used
B)slow speed motors are preferred
C)short time rated motors arc preferred
D)none of the above.

Question 15

15 minute rated motors are suitable for

A)light duty cranes
B)medium duty cranes
C)heavy duty cranes
D)all of the above.

Question 16

Light duty cranes are generally used in

A)automobile workshops
B)pumping stations
C)power houses
D)All of the above.

Question 17

Heavy duty cranes are used in

A)Heavy engineering workshops
B)Steel plants
C)Ore handling plants
D)All of the above.

Question 18

1/2 hour rated motors are used for

A)light duty cranes
B)medium duty cranes
C)heavy duty cranes
D)none of the above.

Question 19

Which of the following drive can be used for derricks and winches ?

A)DC motors with Ward Leonard control
B)AC slip-ring motors with variable resistance
C)Pole changing squirrel cage motors

Question 20

The number of sets used in pole changing type squirrel cage motors for derricks and winches, is

A)2
B)3
C)4
D)6.

Question 21

A pole changing type squirrel cage motor used in derricks has four, eight and twenty four poles. In this the medium speed is used for

A)lifting
B)hoisting
C)lowering
D)landing the load.

Question 22

A pole changing type squirrel cage motor used in derricks has four, eight and twenty four poles. In this the lowest speed is used for

A)lifting
B)hoisting
C)lowering
D)landing the load.

Question 23

For handing fragile articles in a crane

A)low speed is preferred
B)medium speed is preferred
C)high speed is preferr

Question 24

The range of horse power of electric motor drives for rolling mills is of the order of

A)1 to 10 HP
B)15 to 25 HP
C)50 to 100 HP
D)100 to 500 HP.

Question 25

Motors preferred for rolling mill drive is

A)dc motors
B)ac slip ring motors with speed control
C)any of the above
D)none of the above.