ELECTRICAL ENGINEERING IMPORTANT MCQ-INDUSTRIAL DRIVERS

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)    Cost
(e)    All of the above
Ans: e

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)    Speed control range and its nature
(e)    All of the above
Ans: e

3.    Which ofthefollowingmotors is preferred for traction work
?
(a)     Universal motor
(b)     D.C. series motor
(c)    Synchronous motor
(d)    Three-phase induction motor
Ans:

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
Ans: d

5    is preferred for automatic drives.
(a)     Squirrel cage induction motor
(b)     Synchronous motors
(c)    Ward-Leonard controlled D.C. motors
(d)    Any of the above
Ans: c

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
Ans: d

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
Ans: d

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
Ans: d

9.    While selecting an electric motor for a floor mill,
which electrical characteristics will be of least significance ?
(a)    Running characteristics
(b)    Starting characteristics
(c)    Efficiency
(d)    Braking
Ans: d

10.   Which of the following motors are pre-ferred for overhead
travelling cranes ?
(a)    Slow speed motors
(b)    Continuous duty motors
(c)    Short time rated motors
(d)    None of the above
Ans: c

11     is preferred for synthetic fibre mills.
(a)     Synchronous motor
(b)     Reluctance motor
(c)    Series motor
(d)    Shunt motor
Ans: b

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
Ans: c

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
Ans: a

14.   Which part of a motor needs maximum attention for
maintenance ?
(a)     Frame
(b)     Rearing
(c)    Stator winding
(d)    Rotor winding
Ans: b

15    need frequent starting and stopping of electric motors,
(a)     Paper mills
(b)     Grinding mills
(c)    Air-conditioners
(d)    Lifts and hoists
Ans: d

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
Ans: d

17.   _______ motor is a constant speed motor.
(a)    Synchronous motor
(b)    Schrage motor
(c)    Induction motor
(d)    Universal motor
Ans: a

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
Ans: a

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
Ans: d

20    is not a part of ball bearing ?
(a)    Inner race
(b)    Outer race
(c)    Cage
(d)    Bush
Ans: d

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
Ans: d

22.    Rotor of a motor is usually supported on _______
bearings.
(a)     ball or roller
(b)     needle
(c)     bush
(d)     thrust
Ans: a

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
Ans: c

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
Ans: c

25.    A reluctance motor
(a)    is provided with slip rings
(b)    requires starting gear
(c)    has high cost
(d)    is compact
Ans: d

26.    The size of an excavator is usually expressed in terms
of
(a)     ‘crowd’ motion
(b)     angle of swing
(c)    cubic metres
(d)    travel in metres
Ans: c

27.    For blowers which of the following motor is preferred
?
(a)     D.C. series motor
(b)     D.C. shunt motor
(c)    Squirrel cage induction motor
(d)    Wound rotor induction motor
Ans: b

28.    Belted slip ring induction motor is almost invariably
used for
(a)     water pumps
(b)     jaw crushers
(c)    centrifugal blowers
(d)    none of the above
Ans: b

29.    Which of the following is essentially needed while
selecting a motor ?
(a)     Pulley
(b)     Starter
(c)    Foundation pedal
(d)    Bearings
Ans: b

30.    Reluctance motor is a
(a)     variable torque motor
(b)     low torque variable speed motor
(c)    self starting type synchronous motor
(d)    low noise, slow speed motor
Ans: c

31    method of starting a three phase induction motor needs
six terminals.
(a)    Star-delta
(b)    Resistance starting
(c)    Auto-transformer
(d)    None of the above
Ans: a

32.    In ______ method of staging three phase induction
motors the starting voltage is not reduced.
(a)    auto-transformer
(b)    star-delta
(c)    slip ring
(d)    any of the above
Ans: c

33.    In jaw crushers a motor has to often start against
______ load.
(a) heavy
(b) medium
(c) normal
(d) low
Ans: a

34.    For a motor-generator set which of the following
motors will be preferred ?
(a)     Synchronous motor
(b)     Slip ring induction motor
(c)    Pole changing induction motor
(d)    Squirrel cage induction motor
Ans: a

35.    Which of the following motors is usually preferred for
kiln drives ?
(a)     Cascade controlled A.C. motor
(b)     Slip ring induction motor
(c)    Three  phase  shunt  wound 
com-mutator motor
(d)    Any of the above
Ans: d

36.    Heat control switches are used in
(a)    transformers
(b)    cooling ranges
(c)    three phase induction motors
(d)    single phase
Ans: b

37    has relatively wider range of speed control.
(a)     Synchronous motor
(6)     Ship ring induction motor
(c)    Squirrel cage induction motor
(d)    D.C. shunt motor
Ans: d

38.   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)     Star-delta starting
Ans: a

39.    In which of the following applications the load on
motor changes in cyclic order ?
(a)     Electric shovels
(b)     Cranes
(c)     Rolling mills
(d)     All of the above
Ans: d

40.    Flame proof motors are used in
(a)     paper mills
(b)     steel mills
(c)    moist atmospheres
(d)    explosive atmospheres
Ans: d

41.    Which of the following machines has heavy fluctuation
of load ?
(a) Printing machine
(b) Punching machine
(c) Planer
(d) Lathe
Ans: b

42.    For derries and winches which of the following drives
can be used ?
(a)    Pole changing squirrel cage motors
(b)    D.C. motors with Ward-leonard con-trol
(c)    A.C. slip ring motors with variable resistance
(d)    Any of the above
Ans: d

43.    Battery operated scooter for braking uses
(a)     plugging
(b)     mechanical braking
(c)    regenerative braking
(d)    rheostatic braking
Ans: b

44    has least range of speed control.
(a)    Slip ring induction motor
(b)    Synchronous motor
(c)    D.C. shunt motor
(d)    Schrage motor
Ans: b

45    has the least value of starting torque to full load
torque ratio.
(a)    D.C. shunt motor
(b)    D.C. series motor
(c)    Squirrel cage induction motor
(d)     Slip ring induction motor
Ans: c

46.    In case of _______ speed control by injecting e.m.f.
in the rotor circuit is possible,
(a)     d.c. shunt motor
(b)     schrage motor
(c)    synchronous motor
(d)    slip ring induction motor
Ans: d

47.    A pony motor is used for the starting which of the
following motors ?
(a)     Squirel cage induction motor
(b)     Schrage motor
(c)    Synchronous motor
(d)    None of the above
Ans: c

48.    In ________  the  speed can be varied by
changing the position of brushes.
(a)     slip ring motor
(b)     schrage motor
(c)    induction motor
(d)    repulsion motor
Ans: b

49.    In which of the following applications variable speed
operation is preferred ?
(a)     Exhaust fan
(b)     Ceiling fan
(c)     Refrigerator
(d)     Water pump
Ans: b

50.    Heavy duty cranes are used in
(a)    ore handling plants
(b)    steel plants
(c)    heavy engineering workshops
(d)    all of the above
Ans: d

51.    The travelling speed of cranes varies 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
Ans: d

52.    Besides a constant speed a synchronous rotor possesses
which of the following advantages ?
(a)     Lower cost
(b)     Better efficiency
(c)     High power factor
(d)     All of the above
Ans: c

53.    By the use of which of the
followingm    D.C. can be obtained from AC. ?
(a)    Silicon diodes
(b)    Mercury arc rectifier
(c)    Motor generator set
(d)    Any of the above
Ans: d

54.    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
(e)    Synchronous motor
(d)     D.C. motor
Ans: d

55.    Which ofthefollowing motors is preferred when smooth
and precise speed control over a wide range is desired ?
(a)     D.C. motor
(b)     Squirrel cage induction motor
(c)     Wound rotor induction motor
(d)     Synchronous motor
Ans: a

56.    For crane travel which of the following motors is
normally used ?
(a)     Synchronous motor
(b)     D.C. differentially compound motor
(c)    Ward-Leonard controlled D.C. shunt motor
(d)    AC. slip ring motor
Ans: d

57.    The capacity of a crane is expressed in terms of
(a)     type of drive
(b)     span
(c)     tonnes
(d)     any of the above
Ans: c

58.    The characteristics of drive for crane hoisting and
lowering are which of the following ?
(a)     Precise control
(b)     Smooth movement
(c)    Fast speed control
(d)    All of the above
Ans: d

59.    Which of the following motors is preferred for boom
hoist of a travelling crane ?
(a)     Single phase motor
(b)     Synchronous motor
(c)    A.C. slip ring motor
(d)    Ward-Leonard controlled D.C. shunt motor
Ans: c

60.    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
Ans: b

61.    Which of the following motors has series
characteristics ?
(a)     Shaded pole motor
(b)     Repulsion motor
(c)    Capacitor start motor
(d)    None of the above
Ans: b

62.    Which of the following happens when star-delta starter
is used ?
(a)    Starting voltage is reduced
(b)    Starting current is reduced
(c)    Both (a) and (b)
(d)    None of the above
Ans: c

63.    For a D.C. shunt motor which of the following is
incorrect 7
(a)     Unsuitable for heavy duty starting
(b)     Torque varies as armature current
(c)    Torque-armature current is a straight line
(d)    Torque is zero for zero armature current
Ans: a

64.    For which of the following applications motor has to
start with high acceleration?
(a)    Oil expeller
(b)    Floor mill
(c)    Lifts and hoists
(d)    Centrifugal pump
Ans: c

65.    Which of the following types of motor enclosure is
safest ?
(a)    Totally enclosed
(b)    Totally enclosed fan cooled
(c)    Open type
(d)    Semi closed
Ans: b

66.    While selecting motor for an air conditioner which of
the following characteristics is of great importance ?
(a)     Type of bearings
(b)     Type of enclosure
(c)    Noise
(d)    Arrangement for power transmis¬sion
(e)    None of the above
Ans: c

67.    The diameter of the rotor shaft for an  electric
motor depends on which of the following ?
(a)     r.p.m. only
(b)     Horse power only
(c)    Horse power and r.p.m.
(d)    Horse power, r.p.m. and power factor
Ans: c

68.    Which of the following alternatives will be cheaper ?
(a)     A 100 H.P. AC. three phase motor
(b)     Four motors of 25 H.P. each
(c)    Five motors of 20 H.P. each
(d)    Ten motors of 10 H.P. each
Ans: a

69.    The cost of an induction motor will increase as
(a)    horsepower rating increases but r.p.m. decreases
(b)    horsepower rating decreases but r.p.m. increases
(c)    horsepower rating and operating speed increases
(d)    horsepower rating and operating speed decreases
Ans: a

70.    In series motor which of the following methods can be
used for changing the flux per pole ?
(a)    Tapped field control
(b)    Diverter field control
(c)    Series-parallel control
(d)    Any of the above
Ans: d

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