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Lab#2 > Mags > Flashcards

Mags Flashcards

1
Q

Electromagnetic relays are generally sorted into what four categories?

A

Plug in relays
Industrial control relays
Power relays
Low voltage lighting relays

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2
Q

List two types of pins in plug in relays

A

Tubular pins

Spade pins

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3
Q 
Open type to expose contacts are used in which type of relay?
Power relay
Industrial control relay
Low voltage lighting relay
Plug-in relay
A

Power relay

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4
Q

A relays reading maybe classified according to which two agencies?

A

NEMA
National electrical manufacturers association

IEC
International electrical commission

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5
Q

Describe a form c switching arrangement

A

Single pole double throw

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6
Q

Describe or form A switching arrangement

A

Single pole single throw normally open

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7
Q

Describe a form X Switching arrangement

A

Single pole single throw normally open double make

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8
Q

What is the function of armature springs

A

Return the Armature back to its normal position when the coil is D energized

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9
Q

What is the purpose of the contacts Springs

A

To allow the contacts to come together without bouncing and maintain proper pressure on the closed contacts

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10
Q

Name the three components of a contactor

A

Coil core and Armature

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11
Q

What are shading

coils for

A

To reduce the chatter

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12
Q

What is the purpose of laminations

A

To reduce eddy curtains

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13
Q

Name the three main types of contact material

A

Silver cadmium and copper

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14
Q

Describe seal in voltage

A

The voltage at which the Armature completes its full physical travel in the air gap in the magnetic circuit is closed

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15
Q

Describe drop out voltage

A

The voltage at which the air gap in the magnetic circuit opens an Armature drops out

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16
Q

Drop a voltage is approximately how much of rated coil voltage

A

50%

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17
Q

Seal in voltage is approximately how much of rated coil voltage

A

85%

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18
Q

Name 2 types of overloads

A

Thermal

Magnetic flux

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19
Q

What are the four types of elctrical drawings?

A

Block diagram interconnection diagram schematic diagram

wiring diagram

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20
Q

What kind of diagram is a termination schedule?

A

Interconnection diagram

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21
Q

What kind of diagram is a Pin out diagram?

A

An interconnection diagram ( shows how components are connected or wired to other components in the system)

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22
Q

Describe a schematic diagram

A

Also known as a ladder diagram or elementary diagram
shows the sequence of operation
best for troubleshooting

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23
Q

How would interlock in the stop section of a circuit work?

A

It would affect stopping and starting of the circuit

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24
Q

How would interlock affect the start section of a circuit?

A

They affect only the starting of a motor

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25
Q

How does interlock affect the holding circuit?

A

They only affect the running of the motor

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26
Q

Describe an overload device

A

A device affording the protection from excess current, but not necessarily short circuits protection, and capable of automatically opening an electrical circuit

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27
Q

Describe overcurrent device

A

Any device capable of automatically opening an electrical circuit under both predetermined overload and short-circuit conditions either by fusing of metal or by electro mechanical means

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28
Q

Describe low voltage protection

A

The control circuit that does not automatically restore operating voltage two motors or other equipment after a power failure
Also known as three wire control

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29
Q

Describe low-voltage release control

A

A control circuit that automatically restores operating voltage after power outage
Often called a two wire control

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30
Q

Name some things that could prevent a motor from starting

A

No control voltage
Faulty start/stop buttons
Burnt out coil
Open overload contacts

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31
Q

Voltage across a normally closed device that is functioning normally in a live circuit should read

A

0 volts

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32
Q

A voltmeter is preferred the preferred meter to troubleshoot a magnetic motor starter
True or false

A

True

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33
Q

What is a pilot device?

A

A device that signals a change in condition by opening or closing a set of contacts.

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34
Q

What are the two basic contact behaviour types used for pilot control devices

A

Momentary and maintained

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35
Q

What is an automatic pilot device?

A 
A device the detects a change and converts thats change into the opening or closing of a set of contacts.
Temp switch
Float switch
Photelectric
Pressure
36
Q

An over current condition is caused by?

A

A short circuit or overload.

37
Q

Two types of fuses?

A 
Time delayed (dual element)
No time delayed (single element)
38
Q

Two types of circuit breakers?

A 
Instantaneous 
Thermal magnetic (time limit)
39
Q

What are the two types of overcurrent devices?

A

Fuses and circuit breakers

40
Q

What kind of fuse only operates under short circuit conditions?

A

Single element (non time delayed)

41
Q

What kind of circuit breakers provides both short circuit and overload protection?

A

Time limit (thermal magenetic)

42
Q

What is another name for a time limit breaker?

A

Thermal magnetic

43
Q

What is another name for a dual element fuse?

A

Time delayed

44
Q

What is another name for single element fuse?

A

Non time delayed.

45
Q

The ability to open the circuit safely under short circuit conditions without welding contacts or causing a switch explosion is referred to as?

A

Interrupted rating

46
Q

What are the two functions performed by fuses and describe each.

A

Passive function requires the fuse to carry its normal load current continuously without deteriorating due to age or overheating.

Active function required the fuse to open the circuit under abnormal conditions.

47
Q

Name the two parts of a time delay fuse.

A

Thermal cut out

A fuse element or link

48
Q

Which circuit breakers are commonly found panelboards for homes, commercial buildings and industrial plants?

A

Thermal magnetic ( time delayed)

49
Q

True or false

Instantaneous breakers only provide short circuit protection.

A

True

50
Q

Two types of thermal overload devices

A 
Solder pot ( melting alloy)
Bimetallic strip
51
Q

What are the two basic protection requirements for a motor branch circuit?

A

Overcurrent and overload protection.

52
Q

What device protects a motor against short circuits?

A

Overcurrent device

53
Q

Two types of overload devices?

A

Thermal and magnetic flux

54
Q

What are two types of magnetic flux overload devices?

A

Electromagnetic or solid state electronic devices incorporated with transformers.

55
Q

True or false

A short circuit has a higher impedence path than a normal circuit path?

A

False; short circuit has little to no impedence.

56
Q

What are the two types of current ratings?

A

Continuous and interrupted

57
Q

True or false

Time delay fuses are also known as anti surge fuses

A

True

58
Q

The level of current above which a device begins to react to an overcurrent condition is known as its…..

A

Continuous rating

59
Q

Describe interrupted rating.

A

The ability of the device to open the circuit safely under short circuit fault currents without welding contacts or causing a switch explosion

60
Q

True or false
A circuit breaker can have A 15A continuous rating with a 10000A interrupted rating, therefore the device begins to react at overcurrent values of just over 15A and can safely interrupt currents pf up to 10000A.

A

True

61
Q

Desribe the sequence of events that occur to a time delayed fuse responding to a short circuit condition.

A

The fuse link vapourizes and the arc quenching filler extinguishes the arc.

62
Q

The interrupted current depends on…

A

P. Percent impedence of Transformer (%IZ)
I Impedence of the short circuit path.
C. Circuit Voltage
K. kVa rating of the supply transformer

63
Q

Selecting a starter for a motor requires that you know the what characteristics?

A

Horsepower
Full load current (flc)
Service factor (SF)
Voltage of the motor

64
Q

3 types of motor starters?

A

Full voltage (across the line)
Reduced voltage
Reversing

65
Q

Two main components of a magnetic motor starter?

A

Contactor ( electrically operated switch used to open or close the power circuit)

Overload device ( current sensing device that determines when the motor is being overloaded)

66
Q

True or false
3 wire control uses maintained pilot devices and a holding circuit contact. If power is interrupted, the circuit must be reclosed manually.

A

3wire uses momentary pilot devices.

67
Q

2 wire control uses maintaned type of pilot device such as t-stat or float switch. If power is interrupted the circuit will automatically start up upon restoration of power.

A

True

68
Q

Describe the use category Ac-1 IEC starter.

A

High power factor loads, such as heating and general distribution loads.

69
Q

Describe the use category Ac-2 IEC starter.

A

Starting, plugging and inching slip ring motors.

70
Q

Describe the use category Ac-3 IEC starter.

A

Starting and stoppin squirrel cage motors that are stopped under normal running currents.

71
Q

Describe the use category Ac-4 IEC starter.

A

Plugging and jogging (or inching) squirrel cage motors.

72
Q

List 7 factors that affect the heating of a motor

A 
Magnitude of load current
Duration of overload
How frequently motor is starting
Ambient temperature
Time it takes motor to reach speed
Cooling ability of motor
Motor duty cycle ( continuous or jogging)
73
Q

Single phasing in a motor can be caused by.

A

A loose connection
A break one of the motor supply conductors or one of the motor windings
A blown fuse
Burnt out contact in the conductor

74
Q

Describe service factor

A

Indicates the degree to which a motor can withstand periods of overload without damage.

75
Q

At what percentage of it rated load does a three-phase motor stall if the motor is single phasing.

A

35%

76
Q

3 types of timing devices

A
  • Spring wound interval
  • Mechanical and electronic switches
  • Timing relays
77
Q

What are two basic types of timed-contact functions

A

TDOE
Time delay on energization

TDOD
Time delay on de-energization

78
Q

What are 3 methods of controlling the timing of a timing relay

A
  • Fluid dashpot
  • Pneumatic (by air)
  • Electronically
79
Q

What are some additional functions provided by multi function timing relay

A

Interval
One shot
Repeat

80
Q

Describe how tdoe timing relays works

A 
1 energizes
2 time begins
3 time ends
4 contacts change state
5 stay in postion until circuit is manually de energized
81
Q

Describe tdod timing relays

A 
1 energize
2 all contacts change
3 relay is de energized
4 time begins
5 time ends
6 contacts return to og state
82
Q

Describe one shot timing

A
  • occurs when signal is sent to start terminals

- requires power to be applied to relay as well as start terminals

83
Q

Describe interval cycle

A
  • changes timed contacts instantly, but only for a specified time ( on delay)
  • must take away input voltage in order for timing to be reset
84
Q

Describe repeat cycle function

A
  • regular on and off cycle for timed contacts
  • can start in a normal or changed postion
  • on time off/time function
85
Q

True or false
Mechanical and electronic switches have an adjustable trip mechanism or cams that operate contacts. And are fairly accurate.

A

True

Lab#2 (1 decks)

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