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Fourth Year Electrician > Machines > Flashcards

Machines Flashcards

Motor starters, drawings, etc

1
Q

The four basic types of drawings are _____.

A

1: Block
2: Wiring
3: Schematic
4: Interconnection

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2
Q

IEC schematics are drawn with the components on _____ lines.

A

Vertical

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3
Q

There is a single standard legend for electrical drawings, true or false.

A

False

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4
Q

A block diagram shows the _______.

A

Conceptual relationship between equipment or systems

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5
Q

Relationships on a block diagram may be _____ (3 items)

A

1: Physical,.ie elevation
2: Hierarchal, ie speed of response
3: Typical, ie relationship in installation

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6
Q

Wiring diagrams show the _____.

A

Detailed wiring or controls and equipment, related to the actual physical components.

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7
Q

Wiring diagrams show a _____ relationship between components.

A

Practical

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8
Q

A schematic diagram is also sometimes called an _____.

A

Elementary diagram.

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9
Q

Schematic diagrams show _____.

A

Circuit/devices, focused on functional relationship and sequence of operation.

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10
Q

OL contacts in a NEMA motor starter are usually connected between the coil and _____.

A

Line 2.

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11
Q

OL.contacts for IEC motor starters are connected to _____.and are located _____.

A

Terminals 95, 96.

Ahead of the coil

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12
Q

The rung numbers of a ladder style schematic are located on which side of the diagram?

A

Left

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13
Q

Interconnection diagrams show _____.

A

Specific connection details.

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14
Q

The concept of interconnection diagrams can be called the _____ approach.

A

“connect the red wire to terminal 2”

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15
Q

Termination schedules and pin-out diagrams can be _____ diagrams.

A

Interconnection.

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16
Q

Motors may also be required to react to additional perameters such as _____ (4 items).

A

1: Heat
2: Pressure
3: Motion limits
4: Fluid levels in tanks/vessels

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17
Q

Motor starters may require _____.

A

Timing sequences.

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18
Q

The three basic sections of a stop/start circuit are ______.

A

Stop, Start, Holding

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19
Q

Electrical interlocks can enable an operation or _____.

A

Prevent one from occuring.

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20
Q

Contacts connected in the start circuit affect the running of the motor, true or false?

A

False. Only affect starting.

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21
Q

To break a circuit from multiple locations, how must the control circuit be wired?

A

Stop buttons will be NC and in series.

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22
Q

To make a circuit from multiple locations, how does the control circuit need to be wired?

A

Start buttons NO and in parallel.

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23
Q

Overload heaters are placed in the control.circuit to protect the motor in case of an overload, true or false.

A

False

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24
Q

A drawing which shows only the electrical connection between equipment is called _____.

A

Interconnection diagram.

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25
Q

A magnetic motor starter should be used if the motor _____. What are two examples?

A

Has to be repeatedly reversed.

A planer, an elevator

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26
Q

What do the two contactors in a reversing motor starter do?

A

One operates the forward direction and the other operates the reverse.

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27
Q

What would happen if the forward and reverse contactor coils are energized at the same time?

A

It would create a short circuit condition

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28
Q

What will prevent a short circuit condition in a reversing motor starter? How does it work?

A

A mechanical interlocking device

By making it physically impossible for both sets of contacts to be closed at the same time

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29
Q

What happens if the forward and reverse buttons are pressed at the same time, with only mechanical interlocking?

A

One coil pulls in and the other has a current of 4 - 10 times it’s pulled in value.

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30
Q

What will prevent the excessive current in the contactor of a reversing motor starter?

A

Electrical interlocking

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31
Q

Which type of starter is normally already provided with mechanical and electrical interlocks (NEMA or IEC)?

A

NEMA

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32
Q

Seven sections of a control circuit for a reversing starter are:

A

1: General stop
2: Forward stop
3: Reverse stop
4: Forward start
5: Reverse start
6: Forward holding
7: Reverse holding

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33
Q

Electrical interlocks prevent _____.

A

Coil burnout

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34
Q

A standard push button is an example of _____.

A

Momentary contact

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35
Q

What are two examples of selector switches?

A

Standard on/off switch, selector switch

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36
Q

Switches and push buttons are examples of _____.

A

Manually operated pilot control devices

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37
Q

Three examples of automatic pilot devices are:

A

1: Float switches
2: Pressure switches
3: Limit of movement

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38
Q

8 items that can be monitored by automatically operated pilot devices are:

A

1: Movement
2: Pressure
3: Liquid level
4: Thickness
5: Light
6: Rotation
7: Temperature
8: Flow of liquid

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39
Q

What are four pieces of equipment which may require jogging?

A

1: Cranes
2: Hoists
3: Printing Processes
4: Large lathes

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40
Q

What is jogging?

A

When a motor is repeatedly energized in short bursts at rated voltage

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41
Q

What is inching?

A

Motor started at a reduced voltage to let machine creep to desired location

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42
Q

What is positive jogging?

A

When motor can jog regardless off time required

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43
Q

What devices could provide a jog control?

A

Limit switch, proximity switch, other selector switch

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44
Q

What does positive jogging prevent?

A

Prevents holding circuit from energizing if the button is released quickly

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45
Q

How much can the current be during the starting of a 3 phase induction motor?

A

2 - 8 times

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46
Q

A starter that requires jogging duty will normally be sized _____ compared to that for normal operations.

A

One size larger

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47
Q

Why is a starter sized up when a motor is to be jogged?

A

High inrush current that could cause overheating in the contacts

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48
Q

Timers are commonly used in _____ (3 items).

A

HVAC equipment, lighting and commercial fridge & freezers.

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49
Q

What are the three basic types of timing devices?

A

1: Spring wound internal timers
2: Mechanical/electronic time switches
3: Timing relays

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50
Q

Spring wound internal timers are _____ switches, and provide _____.

A

Wall, ‘timed on’

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51
Q

What are some typical uses for spring wound internal timers?

A

Lights, bathtub spa motors and sauna heaters.

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52
Q

What kind of timers use electrically driven clockwork motors? What do those motors control?

A

Mechanical timers. Control adjustable trip mechanisms or cams that operate contacts.

53
Q

What are some applications for mechanical timers?

A

Security lighting, landscape irrigation, parking receptacle circuits.

54
Q

Timing relays are sometimes preferred for _____ and _____ in motor control circuits.

A

Precision and versatility

55
Q

What are three ways a timing relay can be controlled?

A

1: Pneumatic (by air)
2: Electronically
3: Fluid-filled dashpot

56
Q

Pneumatic and fluid filled dashpots operate by controlling the rate of what?

A

A gas or fluid flowing through a hole between two chambers.

57
Q

What are four ways that electronic timing relays are superior to pneumatic and dashpot relays?

A

Smaller, more accurate, versatile, cost-effective

58
Q

What does TDOE mean and how does it work?

A

Time Delay On Energization. Contacts change position at a designated time after the moment the relay is energized.

59
Q

The action of TDOE contacts closing after a set time is called _____ or _____

A

Delay on, delay on operate

60
Q

TDOD means _____.

A

Time Delay On De-energization

61
Q

How do TDOD contacts react when energized?

A

Contacts change immediately when energized, then change back after a set amount of time.

62
Q

The action of TDOD contacts reacting to an energized circuit is called _____ or _____ or.

A

Off delay, delay on release.

63
Q

Selectable time delay settings could be _____ to _____.

A

50 mS to 300 hrs

64
Q

What is an example of TDOE use in a motor?

A

Switching on windings during the starting of part-winding motors.

65
Q

The time delay of a TDOD begins when ______.

A

The coil is de energized

66
Q

If a conveyor belt were run for a set time after the equipment running it has been stopped, this would be considered _____.

A

TDOD

67
Q

What could interval timing be used for?

A

An exhaust fan to purge a combustion chamber before a gas valve opens

68
Q

One shot timing is when power is applied to a relay and a start terminal, and the timing function begins whenever _____.

A

The start terminal receives a signal.

69
Q

Repeat cycle timing provides regular on and off cycles for timed contacts. T or F

A

True

70
Q

The cycle of repeat cycle timing can start when the contacts are in the _____ (normal, changed, or either) position.

A

Either

71
Q

Two separately selectable on/off times may be something like:

A

5 min on, 2 min off, etc

72
Q

Sequential ‘on delay’ starting capabilities may be part of timers with separately selectable times. T or F

A

True

73
Q

Remote manual reset of a timing sequence can be possible using _____.

A

Multi function timing relay

74
Q

Automatic-process-condotion control can be possible with a multi function timing relay by _____.

A

Automatic pilot device that provides feedback to the relay.

75
Q

The electronic timing relay can change over a wye-delta starter in approx _____ mS after the Wye connection has timed out.

A

50

76
Q

How many TDOE contacts are used in a wye-delta starter? Which ones are used?

A
  1. One NC and one NO
77
Q

What is the purpose of the NC interlocks in a Wye-Delta starter?

A

Prevent line-to-line short circuits during start and transition.

78
Q

When a TDOE is first energized what happens to the NO timed contact?

A

Stays open until the the relay times out.

79
Q

What is the state of NC IC contacts in a TDOE when the relay is energized but hasn’t yet timed out?

A

They are open

80
Q

3 additional functions of multi-function timing relays are:

A

1: Interval timing
2: One shot timing
3: Repeat cycle timing

81
Q

When a multi function timing relay is set for one-shot timing, how is the timing period initiated?

A

Signal at the start terminal

82
Q

Why is a timing relay used in a Wye-Delta starter?

A

To allow the motor to come up to speed before changing to Delta.

83
Q

Four examples of applications for electrical motor braking are:

A

1: In an elevator when the brake tension is released when the power is on and applied when power is off
2: To stop a motor before an attempt is made to reverse it, and to prevent a de-energized motor from turning (cranes, hoists).
3: Accurate positioning, quick stops, direction changes in large machine tools
4: Prevent reverse rotation of a de-energized motor (ie ventilation fan)

84
Q

Conveyors, door openers, centrifuges, wood chippers and speed reducers are examples of _____.

A

Motor braking

85
Q

How is the solenoid coil of a friction brake connected with the motor power leads?

A

Parallel

86
Q

Electromagnetic brake release will remove brake friction when the motor is _____.

A

De-energized

87
Q

A solenoid coil for a mechanical friction brake would be connected to (L1 + L2, or T1 + T2).

A

T1 + T2

88
Q

What is dynamic braking?

A

Operate the motor as a generator when the motor needs to be stopped quickly.

89
Q

How is dynamic braking applied?

A

A braking resistor across the armature. Rotation in the motor as it slows generates emf, and current produced opposes the rotation.

90
Q

Dynamic braking in AC motors is called _____.

A

DC injection braking

91
Q

Is there inductive reactance when DC current is applied to the stator winding? What limits the current?

A

No. The resistance of the stator limits the current.

92
Q

The stationary magnetic field created during DC injection braking changes polarity. T or F

A

False

93
Q

In dynamic braking, current induced in the rotor of a SCIM by the stator’s DC magnetic field has what effect? What is the result of this effect?

A

Creates another magnetic field that is attracted to the stator field. This causes the motor to slow.

94
Q

What controls the amount of braking force applied to an AC motor using dynamic braking?

A

DC current supplied to the stator field.

95
Q

Interchanging the supply to two of the stator-phase windings of an induction motor is called _____.

A

Plugging

96
Q

What is the purpose of plugging?

A

Stopping a motor immediately.

97
Q

How does plugging stop a motor?

A

Reversed phase supply causes torque produced in the opposite direction.

98
Q

Plugging is a good way to stop a motor frequently. T or F

A

False. The heat generated can cause overheating/melting in rotor bars.

99
Q

What is anti-plugging?

A

Preventing a motor from reversing until it’s speed has decreased to a specific frequency.

100
Q

What speed does anti-plugging slow a motor to?

A

Near zero

101
Q

Anti-plugging switches are normally _____(open, closed).

A

Closed

102
Q

Nominal line voltages for control transformers are: (4 items)

A

208, 240, 480, 600 AC

103
Q

Typical secondary voltages in control transformers are: (4 items)

A

240, 208, 120, 24 AC

104
Q

Does a control transformer electrically isolate the control circuit from the power circuit?

A

Yes

105
Q

Does a control circuit carry power to the devices it controls?

A

No

106
Q

What are four operating devices of a control circuit?

A

Relays, solenoids, contactor coils, pilot lights

107
Q

What are four pilot devices of a control circuit?

A

Pushbuttons, limit switches, selector switches, proximity switches.

108
Q

DC control circuits require what on the secondary side of the control transformer?

A

A rectifier.

109
Q

Control transformer VA ratings range from _____ to _____.

A

25 VA to 5000 VA

110
Q

Sealed VA is the _____ value.

A

Steady-state

111
Q

Required capacity of a control transformer is calculated with the steady-state VA and the _____.

A

Total inrush VA

112
Q

Low _____ helps reduce the amount of voltage drop in a control transformer.

A

Impedance

113
Q

Outdoor control transformers are _____.

A

Enclosed

114
Q

Open style control transformers must be mounted ______ for safety reasons.

A

Inside an electrical enclosure

115
Q

Are control transformers usually mutual transformers?

A

Yes

116
Q

Control transformers need to be grounded as a system per rule _____ but an exception is provided in subrule for systems less than _____ VA.

A

10-206, (2), 1000

117
Q

What is an acceptable method of grounding a control transformer that is under 1000 VA?

A

To the metal enclosure of the supply, or to the bonding conductor within the enclosure.

118
Q

A control transformer with a secondary voltage of 120 V would be grounded at terminal __.

A

X2

119
Q

Control transformers have ____ inrush current, so _____ fuses should be used for overcurrent protection.

A

High, time-delay

120
Q

Most control transformers are of the _____ type rated at ____ V or less.

A

Dry, 750

121
Q

What is the overcurrent protection requirement for a Class 1 circuit used as a remote control circuit, using #18 AWG wire? And for #16 AWG?

A

5A, 10A.

122
Q

When converting a wiring diagram to schematic, not all of the contactors and relays need to be identified. T or F

A

False. All must be identified

123
Q

All contacts in a diagram conversion must be labelled with _____.

A

Associated relays/contactors

124
Q

Must pilot devices be labelled in a diagram conversion?

A

Yes

125
Q

What ways may conductors be labelled in a diagram conversion?

A

Letters, numbers, colours, other differentiating information

126
Q

The label for a conductor only changes when the conductor is separated from the circuit by _____.

A

A device

127
Q

Pilot lights and coils are examples of _____ devices and are placed on the _____ side of a drawing.

A

Load

128
Q

Devices on the left side of a schematic diagram are called _____, such as contacts of switches.

A

Operating devices

129
Q

In order to minimize the length of wire used overall, the conductor from a controller should first be run to _____.

A

The closest station

Fourth Year Electrician (7 decks)

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