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Dc MachinesB > Defenitions And More > Flashcards

Defenitions And More Flashcards

1
Q

Electron flow theory flow from:
-negative to positive
-positive to negative

A

Negative to positive

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2
Q

Do lines of flux flow from:
-north to south poles
- south to north poles

A

North to south

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3
Q

Where are magnetic lines of flux most densely concentrated at?

A

North and south poles

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4
Q

What is electromagnetism?

A

Current flowing through a conductor creates a magnetic field

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5
Q

What are three factors that determine the strength of an electromagnet?

A

-amount and type of conductor
-magnetic strength of core material
-Amount of current flow

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6
Q

What is a materials ability to become magnetized known as?

A

Permeability

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7
Q

What is a materials resistance to become magnetized knows as?

A

Reluctance

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8
Q

What is magnetism left in a material known as?

A

Residual magnetism

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9
Q

What are two types of magnets?

A

Permanent magnet
Electromagnet

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10
Q

What type of DC machine converts, electrical energy to mechanical energy?

A

Dc Motor

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11
Q

What type of DC machine converts, mechanical energy to electrical energy?

A

DC generator

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12
Q

What are six common DC machine components?

A

Enclosure
Pole pieces
Field windings
Armature assembly
Brushes
Terminals

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13
Q

What is the rotating assembly of a DC machine called?

A

Armature

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14
Q

What type of field windings have many terms of small gauge wire?

A

Shunt field windings

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15
Q

What type of field windings have fewer turns of large gauge wire

A

Series field winding

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16
Q

What components of a DC generator converts AC to DC?

A

Commutator

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17
Q

What is the purpose of field windings in a DC machine?

A

To create magnetic lines of flux

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18
Q

What are three basic types of amateur windings?

A

-Lap wound (low voltage, high current)
-Wave wound (high voltage, low current)
-Frog leg wound (moderate voltage and current)

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19
Q

What are two types of bearings?

A

Sleeve and ball
Roller

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20
Q

What keeps the brushes pressed against the commutator?

A

Brush holder and springs

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21
Q

What part of a DC machine supports the shaft and allows it to rotate?

A

Bearings

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22
Q

Why are some pole pieces curved?

A

To allow for a wider and more even flux distribution

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23
Q

What two materials can brushes be made of?

A

Carbon or graphite

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24
Q

What are three types of field windings in DC machines?

A

-Series
-shunt
-compound

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25
Q

What are the shunt field winding terminals labeled?

A

F1 and F2

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26
Q

What are the series field winding terminals labeled?

A

S1 and S2

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27
Q

What is the mechanical force used to turn a generator?

A

Prime mover

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28
Q

What are four components of an armature assembly?

A

-Shaft
-Iron core
-commutator
-armature windings

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29
Q

What separates the sections of copper on a commutator?

A

Mica insulation

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30
Q

What are four types of enclosures?

A

Open type
Weatherproof
Drip proof
Totally enclosed

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31
Q

According to electron theory, does current flow through an energy source from the positive to the negative terminal?

A

Yes

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32
Q

What’s a DC generator that uses permanent magnets as its field known as?

A

Magneto

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33
Q

What is the portion of the pole piece closest to the armature called?

A

Pole shoe

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34
Q

When proper commutation is taking place, what colour is the commutator?

A

A dark chocolate colour

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35
Q

Typically, which three terminal leads are positive in polarity?

A

A1
S1
F1

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36
Q

How can the ripple effect be smooth in the output of a DC generator?

A

Increasing the number of windings in the armature

37
Q

What are three types of DC machine field structures?

A

Permanent magnet
Separately excited
Self excited

38
Q

When a DC generator contains both series and shunt field windings, what is it called?

A

A compound generator

39
Q

What are three factor factors that determine the output of a generator?

A

Magnetic field strength
Number of conductors in the armature
The speed at which the armature is driven

40
Q

When a conductor cuts through magnetic lines of flux, a voltage is induced into the conductor. What is the principal called?

A

Electromagnetic induction

41
Q

What is the position at which the armature windings are parallel to the lines of flux and there are no induced voltage called?

A

Neutral plane

42
Q

What two magnetic fields interact to cause the amateur to rotate in a DC motor?

A

One created by the current in the amateur winding

One created by the current in the field windings

43
Q

What is the force that causes a motor to rotate known as?

A

Lorentz force

44
Q

What are the windings embedded in slots or holes in the main pole faces called?

A

Compensating windings

45
Q

Is the voltage induced into the armature windings of a DC generator AC or DC?

A

AC

46
Q

What is the distortion, or bending, of the main magnetic field of a DC machine, caused by its interaction with the magnetic flux developed by the armature current called?

A

Armature reaction

47
Q

How is the windings of an Interpol connected in relation to the armature?

A

In series with the armature

48
Q

When a generator supplies current to a load, what is produced, which makes the armature assembly harder to turn?

A

Counter torque or motion action

49
Q

What happens to counter EMF generated as a load is added to a series motor?

A

CEMF increases

50
Q

What are three ways armour reaction can be corrected?

A

Rotate the brushes

Interpose and commutating windings

Compensating windings

51
Q

True or false
The interpose of a DC motor will have the same polarity as the main field poles directly behind them in the direction of rotation ?

A

True

52
Q

What are two main factors that affect the amount of torque developed in a DC motor?

A

Strength of the magnetic field

Amount of current flow

53
Q

Do series motors have extremely low or extremely high starting to torque?

A

Extremely high

54
Q

When a conductor cuts through magnetic lines of flux, voltage is induced in the conductor. What is this principal called?

A

Electromagnetic induction

55
Q

What happens to the torque of DC series motor as the load is increased?

A

Torque increases

56
Q

What happens to the speed of a DC series motor as a load increases

A

Speed decreases

57
Q

In a compound generator, there are two different ways in which shunt windings can be connected to the armature series winding. What are they called?

A

Long shunt

Short shunt

58
Q

What type of compound motor has its field windings wound in such a manner that they oppose each other in the production of magnetism?

A

Differential compound

59
Q

What type of compound motor has its field windings wound in such a manner that they hate each other and production of magnetism?

A

Cumulative compound

60
Q

What are the three characteristic voltage curves for cumulative compound generators called?

A

Over compounded

Flat compounded

Under compounded

61
Q

How is compounding controlled in a compound dc motor or generator?

A

Series field rheostat

62
Q

What happens to torque of a dc series motor as the load is increased?

A

Increases

63
Q

If resistance is added to the shunt field winding circuit, what will happen to the magnetic field?

A

It will decrease

64
Q

If resistance is removed from the shunt field winding circuit of a Dec shunt motor, what will happen to the motor speed?

A

It slows down

65
Q

What type of devices is used for speed control of a dv shunt motor?

A

Shunt field rheostat

66
Q

How can the speed of a dc shunt motor be controlled?

A

By changing the resistance of the shunt field circuit.

67
Q

What is the best way to slow or stop a dc motor under normal operation?

A

Dynamic braking with mechanical brakes

68
Q

The relationship of the Series and shunt fields in a compound generator determines the amount of _____________ for the machine.

A

Compounding

69
Q

What type of compounding is used when constant voltage or speed is required?

A

Flat-compounding

70
Q

How can the output voltage of a dc shunt generator be controlled?

A

Change the resistance of the shunt field circuit

71
Q

How should the direction of rotation of a dc motor be reversed?

A

Interchange A1 and A2

72
Q

What protective device connected in series with the shunt field do most large compound motors have?

A

Field loss relay

73
Q

How is the windings of a interpole connected in relation to the armature?

A

In series

74
Q

What happens to the speed of a dc series motor as the load is increased?

A

Speed decreases

75
Q

What type of compounding occurred when a cumulative long-shunt compound motors full-load speed is greater than its no-load speed?

A

Over compounding

76
Q

What type of compounding occurs when a differential short shunt compound generators full load voltage is less than no load voltage?

A

Under compounding

77
Q

What is the function of the shunt field rheostat?

A

Voltage control for generators and speed control motors

78
Q

What is the function of the series rheostat

A

To control the amount of compounding

79
Q

A motor can be operated as a generator when the motor needs to be slowed or stopped quickly. What is this type of DC motor control called?

A

Dynamic breaking

80
Q

Is resistance and voltage directly or inversely proportional in a DC shunt generator?

A

Inversely proportional

81
Q

Is resistance and speed directly or inversely proportional in a DC shunt motor?

A

Directly proportional

82
Q

What type of armature windings provide high voltage and low current?

A

Wave wound

83
Q

What type of generator is considered a constant voltage generator?

A

Shunt generator or flat compounded

84
Q

In a compound motor, there are two ways in which a shunt winding can be connected to the armature and series windings. What are they called?

A

Long shunt
Short shunt

85
Q

If the current through the shunt field of a large compound motor decreases below a certain level, what protective device disconnects power to the armature?

A

Field loss relay

86
Q

Does an increase in current flow in a conductor result in an increase of magnetic field around the conductor?

A

Yes

87
Q

What causes the shift of the neutral plane on a DC motor under load?

A

Armature reaction

88
Q

If resistance is added to the shunt field, winding circuit of a DC generator, what will happen to the output voltage?

A

It will decrease

89
Q

If resistance is added to the shunt field, winding circuit of a DC generator, what will happen to the output voltage?

A

It will decrease

Dc MachinesB (1 decks)

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