Deck 1: Electric Motors: Selection, Types, and Applications

Question 1

The selection of an electric motor for any application depends on which of the following factors ?

A)Electrical characteristics
B)Mechanical characteristics
C)Size and rating of motors
D)All of the above

Answer 1

All of the above

Question 2

For a particular application the type of electric-and control gear are determined by which of the following considerations ?

A)Starting torque
B)Conditions of environment
C)Limitation on starting current
D)All of the above

Answer 2

All of the above

Question 3

Which of the following motors is preferred for traction work ?

A)Universal motor
B)D.C.series motor
C)Synchronous motor
D)Three-phase induction motor

Answer 3

D.C.series motor

Question 4

Which of the following motors always starts on load ?

A)Conveyor motor
B)Floor mill motor
C)Fan motor
D)All of the above

Question 5

is preferred for automatic drives.

A)Squirrel cage induction motor
B)Synchronous motors
C)Ward-Leonard controlled
D)C.motors

Question 6

When the load is above a synchronous motor is found to be more economical.

A)2 kW
B)20 kW
C)50 kW
D)100 kW

Question 7

The load cycle for a motor driving a power press will be

A)variable load
B)continuous
C)continuous but periodical
D)intermittent and variable load

Question 8

Light duty cranes are used in which of the following ?

A)Power houses
B)Pumping stations
C)Automobile workshops
D)All of the above

Question 9

While selecting an electric motor for a floor mill, which electrical characteristics will be of least significance ?

A)Running characteristic
B)Starting characteristics
C)Efficiency
D)Braking

Question 10

Which of the following motors are pre-ferred for overhead travelling cranes ?

A)Slow speed motor
B)Continuous duty motors
C)Short time rated motors
D)None of the above

Question 11

is preferred for synthetic fibre mills.

A)Synchronous motor
B)Reluctance motor
C)Series motor
D)Shunt motor

Question 12

Ward-Leonard controlled D.C. drives are generally used for excavators.

A)Light duty
B)Medium duty
C)Heavy duty
D)All of the above

Question 13

Which of the following motors is used for elevators ?

A)Induction motor
B)Synchronous motor
C)Capacitor start single phase motor
D)Any of the above

Question 14

Which part of a motor needs maximum attention for maintenance ?

A)Frame
B)Rearing
C)Stator winding
D)Rotor winding

Question 15

need frequent starting and stopping of electric motors,

A)Paper mills
B)Grinding mills
C)Air-conditioners
D)Lifts and hoists

Question 16

Which feature, while selecting a.motor for centrifugal pump, will be of least significance ?

A)Starting characteristics
B)Operating speed
C)Horse power
D)Speed control

Question 17

motor is a constant speed motor.

A)Synchronous motor
B)Schrage motor
C)Induction motor
D)Universal motor

Question 18

The starting torque in case of centrifugal pumps is generally

A)less than running torque
B)same as running torque
C)slightly more than running torque
D)double the running torque

Question 19

Which of the following motors are best for the rolling mills ?

A)Single phase motors
B)Squirrel cage induction motors
C)Slip ring induction motors
D)D.C.motors

Question 20

is not a part of ball bearing ?

A)Inner race
B)Outer race
C)Cage
D)Bush

Question 21

The starting torque of a D.C. motor is independent of which of the following?

A)Flux
B)Armature current
C)Flux and armature current
D)Speed

Question 22

Rotor of a motor is usually supported on bearings.

A)ball or roller
B)needle
C)bush
D)thrust

Question 23

For which of the following applications D.C. motors are still preferred?

A)High efficiency operation
B)Reversibility
C)Variable speed drive
D)High starting torque

Question 24

In a paper mill where constant speed is required

A)synchronous motors are preferred
B)A.C.motors are preferred
C)individual drive is preferred
D)group drive is preferred

Question 25

A reluctance motor

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