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Electrical Machine 1
  • Mary Jane Suarez

  • 問題数 60 • 11/19/2024

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    問題一覧

  • 1

    By looking p at which part of the shunt motor, it can be easily confirmed that a particular motor is DC Motor

    Commutator

  • 2

    If a speed of a DC shunt motor is increased, the back emf of the motor will

    increase

  • 3

    As the load is increased the speed of DC shunt motor will

    reduced slightly

  • 4

    It is a DC motor that tends to over speed when the field opened while running

    shunt motor

  • 5

    A DC shunt motor is rotating in clockwise direction as viewee from one end. The polarity of connection of the armature and field winding are reversed simultaneously. The motor will

    rotate in clockwise direction

  • 6

    DC shunt motors are used for driving

    machine tools

  • 7

    Which of the following statement is correct in case of a DC Series Motor

    It should be directly connected to the load

  • 8

    If the current in the armature of dc series is reduced to 50% the torque of the motor will become

    25% of the previous value

  • 9

    Which DC Motor will be preffered for elevators

    Cumulative Compound Motor

  • 10

    For both lap and wave windings, there are as many commulator bars as the number of

    winding elements

  • 11

    For a DC Generator when the number of poles and the number of armature conductors is fixed, then which winding will give higher emf?

    wave winding

  • 12

    Which of the following components of DC generator plays vital role for providing direct current of a DC Generator

    Commulator

  • 13

    In DC generators, lap winding is used for

    low voltage, high current

  • 14

    In a DC generator the critical resistance refers to the resistance of

    field

  • 15

    The number of armature parallel in two pole DC Generator having duplex lap

    4

  • 16

    The number of armature parallel paths in two pole DC Generator having duplex winding is

    4

  • 17

    If the armature of an eight-pole dc machine were wound with a simplex wave winding, how many parallel paths would there be?

    2 paths

  • 18

    The direction of rotation of a dc motor is reversed by

    reversing armature connections

  • 19

    Which of the following loss in a DC generator varies significantly with the load current?

    armature copper loss

  • 20

    If Bmax is the maximum flux density, then addy current loss will vary as

    (Bmax)2

  • 21

    The hysteresis loss in DC generator with the frequency of magnetic reversals as

    f

  • 22

    In case of DC machines, mechanical losses are primary function of

    speed

  • 23

    In which of the following application DC series motor is invariably used?

    starter for a car

  • 24

    A DC series motor, as compared to shunt and compound motors, has the highest torque at the start because if its comparatively

    stronger series filed

  • 25

    A series motor is best suited for driving

    cranes and hoists

  • 26

    Which DC motor will be suitable along with flywheel for intermittent light and heavy loads?

    cumulatively compounded motor

  • 27

    Differentially compound DC motors can find applications requiring

    low starting torque

  • 28

    In an overload motor main danger arises due to

    winding getting overheated

  • 29

    No-load speed of which of the following motor will be highest?

    series motor

  • 30

    A shearing machine has cyclic load consisting of intrpermittent ligth and heavy loads. Which of the following DC motor suitable for this purpose?

    cumulative compound motor

  • 31

    The ratic of starting torque to full-load torque is least in case of

    shunt motor

  • 32

    The type of DC motor used for shears and punches is

    cumulative compound DC motor.

  • 33

    Which DC motor will have keast percentage increase of input current p, for the same percentage increase in the toque

    series motor

  • 34

    These day DC motor are widely used in

    electic traction

  • 35

    The direction of rotation of a DC series motor can be changed by

    intercharging field terminals

  • 36

    If a DC motor is to be selected for conveyors, which motor would be preferred

    series motor

  • 37

    Which DC motor will be preferred for constant speeed line shafting?

    Shunt motor

  • 38

    A DC generetor works on the principle of

    Faraday’s law of eletromagnetic induction

  • 39

    For generating large current on DC generators which winding is generally preferred?

    lap winding

  • 40

    In case of DC machine winding, number of commutater segment is equal to

    number of armature coils

  • 41

    The purpose providing dummy coils in a generator is

    to provide mechanical balance for the rotor

  • 42

    In a DC generator the critical resistance to the resistance of

    field

  • 43

    In a DC generator in order to reduce sparking at brushes p,the self-induced emf in the coil is neutralized by all of the following except

    dummy coil

  • 44

    Interpoles are connected _____ with the armature and compensating windings are connecties in _____ with the armature

    series, series

  • 45

    In a DC machine stray loss is the sum of

    Iron loss and mechanical loss

  • 46

    Which of the following losses are significantly reduced by laminating the core of a DC generator

    Eddy current losses

  • 47

    If residual magnetism of a shunt generator is destroyed accidentally, it may be restored by connecting its shunt field

    To a battery

  • 48

    One dc motor drives another de motor. The second dc motor when excited and driven

    Runs as a generator

  • 49

    In over compound generato, full load terminal voltage is

    More than no-load terminal voltage

  • 50

    The series field of a short-shunt DC generator is excited by

    load current

  • 51

    Whem the shunt field of a compound generator is connected across both series field and armature.suah a connection is known as

    Long shunt

  • 52

    Drop speed of a DC generator due to increase in load can be compensated by

    Increase the input to prime mover

  • 53

    Lamination of core are generally made of

    silicon steel

  • 54

    the field of DC generators are usually made of

    copper

  • 55

    The bearings used to support the rotor shatfs are geneally

    ball bearings

  • 56

    Brushes of DC machine are made of

    carbon

  • 57

    The insulting material used between the comutator segment is normally

    mica

  • 58

    Welding generator will have

    lap winding

  • 59

    In case of DC machine winding,number of commutator segmentis equal to

    number of armature coils

  • 60

    Which one of the following generators is used for charging batteries?

    shunt