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Magnetics Controls and Switching > Electrical Control Drawings > Flashcards

Electrical Control Drawings Flashcards

1
Q

Which control drawing is the best for troubleshooting?

A

Schematic

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2
Q

Which drawing is the best for wire count?

A

Block

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3
Q

Which control drawing is the most realistic?

A

Wiring

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4
Q

What are two types of interconnection diagrams?

A

Termination Schedule

Pin Out

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5
Q

What is the difference between a relay and contactor?

A

Contactors are used in higher current applications. Fundamentally they are the same.

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6
Q

What are the basic electromagnetic relay categories?

A

Plug In Relays
Industrial Control
Power Relays
Low Voltage Lighting Relays

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7
Q

Which relay has exposed contacts and are rated for up to 30 Amps?

A

Power Relays

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8
Q

Low voltage lighting relays have coils that operate at less than ____ V.

A

30

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9
Q

Definite purpose contactors are designed for use in the ______ industry.

A

HVAC

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10
Q

Coils have what type of ratings?

A

Voltage

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11
Q

Contacts have 3 types of ratings. What are they?

A

Horsepower
Current
Voltage

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12
Q

Form A, B, C, X and Y refer to what?

A

Contact arrangement

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13
Q

The three main parts of a relay or contactor are…?

A

Coil
Core
Armature

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14
Q

What is the purpose of armature springs?

A

Return the armature back to its original position when the coil is de-energized

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15
Q

What is the purpose of the contact springs

A

Absorb the shock of closing and maintaining a constant pressure

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16
Q

Laminations in the iron or steel armature core are there to

A

Reduce eddy currents

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17
Q

What is the purpose of a shading coil

A

Reduce chattering

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18
Q

Three types of contact materials are

A

Silver
Copper
Cadmium

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19
Q

What contact material is self cleaning?

A

Silver

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20
Q

What contact material is good for frequent switching?

A

Cadmium

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21
Q

What contact material is prone to pitting?

A

Copper

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22
Q

Bridge contacts reduce what?

A

Arching between the contacts

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23
Q

How many places do bridge contacts open and close?

A

Two

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24
Q

Seal in voltage is ______ % of the rated __________ of the coil.

A

Seal in voltage is 85 % of the rated voltage of the coil.

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25
Q

Drop out voltage is ______ % of the rated __________ of the coil.

A

Drop out voltage is 50% of the rated voltage of the coil.

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26
Q

What are some affects of of low voltage in respect to coils?

A

Chattering
Burnt out coil
Not enough power to pull in armature

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27
Q

What happens when high voltage in respect to coils?

A

Damaged contacts due to violent armature pull in

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28
Q

Supply voltage to an operating coil should never exceed _______ % of its rated value.

A

110%

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29
Q

What is overcurrent?

A

Current above rated

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30
Q

What are two conditions that can cause overcurrent

A

Short circuit

Overload

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31
Q

Define short circuit

A

A low impedence path to ground

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32
Q

Define overload

A

A level of overcurrent above rated voltage for a prolonged period of time

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33
Q

What are two types of overcurrent devices?

A

Circuit Breaker

Fuse

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34
Q

What is the most common type of fuse?

A

Cartridge

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35
Q

What is the most common type of circuit breaker?

A

Thermal Magnetic (time delay)

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36
Q

Non time delay fuses protect against overloads?

True or False

A

False

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37
Q

Time delay fuses are also known as single element fuses?

True or False

A

False; they are Dual Element fuses

38
Q

Time delay fuses have two parts, a thermal cut out to protect against overloads and a fuse link to protect against short circuits.

True or False

39
Q

Describe Thermal Cut Out

A

One part of a time delay fuse or Thermal Magnetic CCT breaker, it allows for brief overloads (momentary inrush current when motor starts) and responds with inverse time characteristics (the higher the value of overload the quicker the fuse opens)

40
Q

Instantaneous Circuit breakers protect against short circuit conditions only?

True or False

41
Q

Thermal Magnetic circuit breakers are also referred to as Time Limit circuit breakers

True or False

42
Q

Thermal magnetic circuit breakers provide protection from short circuit and overload conditions?

True or False

43
Q

Instantaneous circuit breakers are the most common type?

True or False

A

False; Thermal Magnetic are.

44
Q

What rating is marked on the handle of a breaker?

A

Continuous

45
Q

The ability of a device to open a circuit SAFELY under short circuit fault currents without welding contacts or causing a switch explosion is called its:

A

Interrupting Rating

46
Q

The four factors of short circuit (fault) current are:

A

Percent impedence of transformer
Impedence of the short circuit path
Circuit Voltage
KVA of transformer

P.I.C.K.

47
Q

The four main disconnection means for a motor branch circuit are

A

Manual motor starter switch
Fused disconnect
Circuit breaker
Cord

48
Q

What does FLA stand for?

A

Full Load Amps

49
Q

What does FLC stand for?

A

Full load Current

50
Q

Motor circuits have two protections, what are they?

A

Overcurrent

Overload

51
Q

To select a motor circuit overcurrent device you must know 3 things about the installation

A

FLA
Type of motor
Type of overcurrent

52
Q

A motor has a FLA of 24 and a SF of 1.15. Size the overload device.

53
Q

What are the two main parts of a magnetic motor starter

A

Contactor

Overload

54
Q

What is the purpose of the holding (maintained) contact

A

Maintain a path of current when start is released

55
Q

What must you know to select a starter for a particular motor

A

Horsepower
Voltage
FLA
Service Factor

56
Q

What is the smallest NEMA starter you can buy?

57
Q

What are the three types of magnetic motor starters

A

Full Voltage
Reduced Voltage
Reversed Voltage

58
Q

What connection points are between the holding contacts of a NEMA starter?

59
Q

What are the connection points between the holding contacts of a IEC starter?

60
Q

Single phasing of a 3-phase motor is the loss of one of the phases

True or False

61
Q

What is the purpose of an overload device

A

To protect the motor

62
Q

What are the two main types of overload devices

A

Thermal

Magnetic Flux

63
Q

A bimetallic strip overload device has an adjustable setting?

True or False

64
Q

Melting alloy type overload devices are of the magnetic flux type?

True or False

65
Q

Magnetic flux overload devices operate by detecting an increased magnetic flux created by motor current?

True or False

66
Q

What are the 3 sections for a basic stop start station for the control of a motor?

A

Stop
Start
Holding

67
Q

The purpose of interlocking is to allow the operation of one device to be controlled by the condition of another device?

True or False

68
Q

In a multiple stop start station controlling a motor, how are the stop buttons connected?

69
Q

How are start buttons connected

70
Q

Define low voltage release

A

Two Wire control. The load will be energized when power restores after outage.

71
Q

Define low voltage protection

A

Three wire control, will not automatically come on after power outage.

72
Q

A pilot device ________ a change in condition by opening or closing a set of contacts

A

signals a change

73
Q

Automatic pilot devices __________ a change and converts this change to the opening or closing of a set of contacts

A

detects a change

74
Q

A normally closed float switch, closes on a rise in liquid?

True or False

75
Q

A reversing magnetic motor starter contains two contactors and two overload devices?

True or False

A

False; Two contactors and one overload

76
Q

To change the direction of a three phase squirrel cage induction motor, interchange any two of the lines to the motor.

True or False

77
Q

What is the purpose of mechanical interlock

A

Prevent both armatures from being engaged at the same time

78
Q

Mechanical interlock comes standard on all NEMA prewired starters.

True or False

A

False; only sized 00 to 5

79
Q

What is the purpose of electrical interlock?

A

Prevent both coils from energizing simultaneously

80
Q

On a prewired NEMA reversing motor starter the terminal connections between the holding contacts for the reverse contactor are labelled

81
Q

How many sections for interlock contacts are there in a reversing motor starter schematic? What are they?

A

7

1 - General Stop
2- Fwd/Rev Stop
2- Fwd/Rev Start
2- Fwd/Rev Holding

82
Q

What is the purpose of push button interlock?

A

So you don’y have to push stop

83
Q

What are three basic types of timing devices

A

Spring Wound
Mechanical and Electric
Timing Relays

84
Q

What type of timing device has a 24 hour, or 7 day timing cycle.

A

Mechanical or Electric

85
Q

What does TDOD stand for

A

Time Delay on DeEnergization

86
Q

What does TDOE stand for

A

Time Delay on Energization

87
Q

A normally open TDOE timed contacts will change state the instant the coil is energized

True or False

88
Q

A NC TDOD will be closed after a set time when the coil is deeneergized

True or False

89
Q

Name 3 other timed contact functions

A

Repeat
One Shot
Interval

90
Q

Name 2 languages used for writing programs for smart relays.

A

Ladder Logic

Function Block

91
Q

What are the four basic types of control drawings?

A

Wiring Diagram
Schematic
Block
Interconnection

Magnetics Controls and Switching (1 decks)

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