Deck 6: Electric Motors and Drives: Exploring Speed, Control, and Efficiency

Question 1

The travelling speed of cranes varies from from

A)20 to 30 m/s
B)10 to 15 m/s
C)5 to 10 m/s
D)1 to 2.5 m/s

Answer 1

1 to 2.5 m/s

Question 2

Which of the following motors is preferred when quick speed reversal is the main consideration?

A)Squirrel cage induction motor
B)Wound rotor induction motor
C)Synchronous motor
D)DC motor

Answer 2

DC motor

Question 3

Which off the following motors is preferred when a smooth and resize speed control over a wide range is desired?

A)DC motor
B)Squirrel cage induction motor
C)Wound rotor induction motor
D)Synchronous motor

Answer 3

DC motor

Question 4

Which of the following machines has heavy fluctuating of load ?

A)Printing machine
B)Punching machine
C)Planer
D)Lathe

Question 5

Which of the following motors is usually preferred for kiln drives?

A)Cascade controlled AC motor
B)Slip ring induction motor
C)Three phase shunt wound commutator motor
D)Any of the above

Question 6

In squirrel cage induction motors which of the following methods of starting cannot be used ?

A)Resistance in rotor circuit
B)Resistance in stator circuit
C)Auto transformer starting
D)Start Delta starting

Question 7

Electric drive is becoming more and more popular because

A)It is simple, cleaned, compact and reliable
B)It provides easy and smooth control, flexibility in layout, easy starting and facility for remote control
C)It is cheaper in initial as well as in maintenance cost
D)All of the above

Question 8

The basic elements of an electric drive are

A)Electric motor and the transmission system
B)Electric motor, the transmission and control system
C)The transmission and control system
D)Electric motor and conversion equipment

Question 9

Introduction of automation in production process has become possible only because of the use of

A)An electric drive
B)Group drives
C)Individual and multi motor drives
D)Individual Drive

Question 10

DC motor are still preferred for use in

A)Electric excavators, steel mills and cranes
B)Lathes and machine tools
C)Flour Mills and Jaw crushers
D)Paper industry

Question 11

A typical active load is

A)Hoist
B)Lathe
C)Blower
D)Pump

Question 12

In jaw crushers, a motor has to often start against

A)low load
B)medium load
C)normal load
D)heavy load.

Question 13

Motor used for elevators is generally

A)synchronous motor
B)induction motor
C)capacitor start single phase motor

Question 14

In synthetic fibre mills motor with

A)constant speeds are preferred
B)high starting torque are preferred
C)variable speed are preferred
D)low starting torque are preferred.

Question 15

Which of the following motor is preferred for synthetic fibre mills ?

A)series motor
B)reluctance motor
C)shunt motor
D)synchronous motor.

Question 16

Reluctance motor is a

A)self-starting type synchronous motors
B)low torque variable speed motor
C)variable torque motor
D)low noise, slow speed motor.

Question 17

A reluctance motor

A)is compact
B)has high cost
C)requires starting gear
D)is provided with slip rings.

Question 18

Power factor in case of reluctance motor is

A)nearly unity
B)always leading
C)0.8
D)0.3 to 0.4.

Question 19

The efficiency of reluctance motor is around

A)95%
B)90%
C)75 to 85%
D)60 to 75%.

Question 20

A reluctance motor on over-load runs as

A)synchronous motor
B)induction motor
C)either of the two.
D)all of the above.

Question 21

The size of a excavator is usually expressed in terms of

A)cubic meters
B)travel in meters
C)angle of swing
D)'crowd' motion

Question 22

Ward-Leonard controlled dc drives are generally used for

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

Question 23

Which electromagnet is preferred for noiseless operation

A)DC operated
B)AC operated
C)all of the above

Question 24

For high frequency choppers the device that is preferred is

A)Thyristor
B)TRIAC
C)Transistor
D)GTO.