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Motor Control > Motor Control > Flashcards

Motor Control Flashcards

1
Q

The most important reason for interlocking the S contact and the 2M contact in a wye-delta start is too

A

Prevent a line short

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2
Q

A fridge units for a walk in freeze should use LVR or LVP

A

LVR

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3
Q

A dual voltage motor connected to it’s higher voltage will use a __________ current rated OL heaters

A

Lower

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4
Q

In an overload condition the folding contact of a 3 wire will be open yes or no

A

Yes

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5
Q

Is a shading coil is required for a 120v coil really

A

Yes

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6
Q

What is the difference to a schematic and a power CCT diagram

A

A power CCT is represented as a single line

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7
Q

Regarding a NO float switch what defines it’s normal

A

Not enough liquid to close the circuit

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8
Q

Where is the holding contact located in a 3 wire CCT physically

A

The motor contactor

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9
Q

A standard 2 wire does not provide….

A

Low voltage protection

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10
Q

The least accurate timing cycle is the…..

A

Hydraulic timer

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11
Q

What power CCT component normally provides both start and stop functions

A

Contactor

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12
Q

The over current devices in the power CCT of a scim provide

A

Line to line ground fault protection

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13
Q

If a control transformer is used to step down a control circuit where would the best place be to come off of the power CCT

A

L1-L2 on the line side of motor contactor

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14
Q

What type of contact from an overload relay will provide an indicator light when the OL is tripped

A

NO OL

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15
Q

A TD relay can only contain only time delay contacts true or false

A

False

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16
Q

A limit switch is a device that operates by physical contact T/F

A

True

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17
Q

An inductive type proximity sensor detects the presence of almost any material T/F

A

False

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18
Q

The electrical interlocks in a F/R Control circuit will lot prevent a motor from changing directions without coming to a complete stop
T/F

A

True

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19
Q

FLA÷√3 will give the current to be used to determine OL rating for a WYE-Delta T/F

A

True

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20
Q

A WYE-Delta starter needs six conductors between the motor and controller because each scr must be connected individually T/F

A

False

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21
Q

In an overload replay the NC control contact sense excessive conductor temperature T/F

A

False

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22
Q

The jog circuit problem of a mechanical race is easily fixed by a CR T/F

A

True

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23
Q

Plugging is the most effective form of braking and is achieved by reversing any two stator leads T/F

A

True

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24
Q

Why is an induction motor more commonly controlled by an across the line starter

A

High starting torque low cost and simple construction

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25
Q

A switch not meant to start or stop any load is called a?

A

Isolating switch

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26
Q

What hazard is present by using a timer to design a plugg control circuit

A

A change in load could cause the motor to accidentally be run backwards

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27
Q

What braking method requires a reversing controller

A

Plugging

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28
Q

How can the amount of braking torque be adjusted when using dynamic braking

A

Adjust field strength

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29
Q

What are 5 categories of deceleration methods

A

Friction
Plugging
DC injection
Dynamic
Eddy current
Regenerative

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30
Q

What are four key concepts with respect to electrical controller maintenance

A

Clean
Dry
Tighten connections
Friction free moving parts

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31
Q

What is the main disadvantage of a reduced voltage starter

A

Insufficient torque

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32
Q

What does nema stand for

A

National electrical manufacturing association

33
Q

Nema controllers are rated in

A

HP

34
Q

Nema controller ratings are

A

00-8

35
Q

How much horsepower is a nema #8

A

900hp

36
Q

What does IEC stand for

A

International Electrotechnical commission

37
Q

What is the power rating used for IECs

A

Watts

38
Q

What system is used for IEC controllers sizing

A

A-Z

39
Q

A starter that contains a disconnect, oc, contactors and OL in one enclosure is called

A

A combination starter

40
Q

Motors take up what percentage of the electrical field

A

46%

41
Q

What is a cabinet that contains multiple motor circuits

A

Motor control centre or MCC

42
Q

What are required functions of motor control

A

Safety
Starting motor
Stopping motor
Motor current protection
Surge protection
Reversing
Speed control
Jogging
Inching

43
Q

A motor control that has physical operation of the start at the location of the actual controller is a

A

Manuel controller

44
Q

A control circuit with automatic restart and 2 wire control is a

A

Semi automatic

45
Q

A two wire control circuit provides

A

Low voltage release

46
Q

A control circuit that has no auto restart is a

A

Automatic control

47
Q

A 3 wire control circuit provides

A

Low voltage protection

48
Q

What are the three types of timers

A

Hydraulic
Pneumatic
Electrical

49
Q

What time does this describe
Accurate
Inexpensive
Many operating modes

A

Electric timer

50
Q

What timer does this describe
Very accurate with robust build
And expensive

A

Pneumatic timer

51
Q

What stopping method is the most efficient

A

Plugging

52
Q

Starting a motor in FVS has the benefit of

A

Higher starting torque

53
Q

What is the benefit of a RVS

A

Lowered inrush current

54
Q

What are the RVS that are always closed transition

A

Primary resistive
Primary impedance

55
Q

T/F a autotransformer start can only be closed transition

A

False

56
Q

T/F a wye delta start can be both closed and open transition

A

True

57
Q

A primary resistive start has a minimum of how many stages

A

2

58
Q

Starting a motor in a open transition starter can cause

A

Line disturbances

59
Q

What RVs provides the highest amount of torque per amp of primary current

A

Auto transformer

60
Q

A wye delta start only works on a motor with ______ and _______ leads

A

6 and 12

61
Q

The OL device of a wye delta starter is bases of of

A

Phase current of delta

62
Q

An electronic soft start is a ___________ transition

A

Closed

63
Q

A soft start only provides what

A

Voltage control

64
Q

What do pilot devices do

A

Devices that direct current to its destination

65
Q

Which vfd utilizes a choke and a capacitor in DC link

A

VVI

66
Q

CSI vfd are ____________ in size

A

Large

67
Q

CSI are used generally for __________ motors

A

Large

68
Q

PWM VFD provides the closest ________________

A

Sinosoidal wave

69
Q

In regards to a VFD what should you consider when running a motor at low speeds

A

Heat build up in motor

70
Q

Warning on a vfd will / will not result in shutdown

A

Will not

71
Q

Fault on a VFD will / will not result in shutdown

A

Will

72
Q

When sizing a VFD it’s best to ___________ the VFD

A

Oversize

73
Q

When using a drive with 1ø it has to be derated by _______

A

50%

74
Q

What are the main parts of the VFD

A

Converter
DC link
Inverter
Control processor

75
Q

What parts do the converter contain

A

Diodes
Scr’s

76
Q

What does the DC link do

A

Filtering

77
Q

What does the inverter do

A

Switching

78
Q

What is the formula for V/HZ

A

V÷HZ

Motor Control (1 decks)

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