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MOTOR CONTROL FUNDAMENTALS > WORKSHEET #3 > Flashcards

WORKSHEET #3 Flashcards

1
Q

What is the name of the devices described as electromechanical switches that are referred to as Auxiliary contacts?

A

Contactor

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2
Q

What are the 2 main components that make up a contactor?

A
  1. Electromagnet
  2. Contacts
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3
Q

Please draw the NEMA symbol for the 2 components of a contactor that is considered normally open.

A

N/A

This requires a visual representation.

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4
Q

If a contactor is one device, then why do we require 2 separate symbols?

A

To represent the different functions of the components.

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5
Q

What is the difference between electrically connected and mechanically connected?

A

Electrically connected refers to components that are linked by electrical pathways, while mechanically connected refers to components that are linked by physical means.

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6
Q

What are the components of the contractor labeled L1, T1 - L2, T2 – L3, T3 called?

A

They are called contacts.

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7
Q

How should the IEC symbols for the contacts be drawn?

A

The symbols should be drawn vertically, in a de-energized state, and labeled correctly.

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8
Q

What do the #1 and #6 represent in L1 and T3?

A

1 and #6 represent specific identifiers for the contacts. They are not included in drawings for simplicity.

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9
Q

What do the L and T stand for?

A

L stands for line and T stands for terminal. The feeder or incoming wires are attached to the L terminals.

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10
Q

Are L1 and T1 electrically or mechanically connected to the other 2 poles of the contactor?

A

They are electrically connected.

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11
Q

How are L1 and T1 connected to each other?

A

They are connected through electrical circuitry.

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12
Q

By what methods do we connect our conductors to the contacts portion of the contactor?

A

Conductors are connected using terminal screws or connectors.

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13
Q

What is the black square in the center of the image?

A

The black square represents the coil of the contactor. It energizes to close the contacts.

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14
Q

What is the typical form of contactors?

A

Contactors can come in many forms, typically normally open (NO).

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15
Q

How can electricians verify the contacts’ de-energized state?

A

Electricians can verify the contacts’ de-energized state by checking the device.

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16
Q

Will there ever be continuity between L1, T2, and L3 when there are no wires attached to the device?

A

At any point, there will not be continuity between L1, T2, and L3 when there are no wires attached.

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17
Q

What are the silver metal parts with screws on one side called?

A

These are terminals.

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18
Q

How does a contactor work?

A

A contactor operates by using an electromagnetic coil to open or close contacts, thereby controlling the flow of electricity in a circuit.

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19
Q

Do contactors come with different coil voltages?

A

Yes, contactors are available in various coil voltages, which can be either AC or DC.

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20
Q

What happens if we apply 240Vac to the coil?

A

Applying 240Vac to the coil may damage the contactor or cause it to malfunction.

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21
Q

What happens if we apply 24Vac to the coil?

A

Applying 24Vac to the coil will activate the contactor, allowing it to control the connected load.

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22
Q

What is the maximum ampacity for resistive loads through the contactor’s contacts?

A

The maximum ampacity depends on the contactor’s specifications and ratings, typically defined for resistive loads like lighting or heating.

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23
Q

Can this contactor control the motor shown on the nameplate?

A

To determine if the contactor can control the motor, compare the contactor’s ratings with the motor’s requirements.

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24
Q

What is the horsepower rating for the motor? Show your work.

A

To calculate horsepower, divide the motor’s wattage by 735.499.

Example: If the motor is rated at 1470 Watts, then 1470 / 735.499 = 2 Hp.

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25
What is the maximum voltage that can pass through the contacts of our contactor?
The maximum voltage is specified by the contactor's design and ratings.
26
What is the maximum Full Load Amps (FLA) that can pass through the contacts?
The maximum FLA is defined by the contactor's specifications and must not be exceeded.
27
Can we run different voltages and ampacities through each pole of our contactor?
Yes, as long as we don’t exceed the voltage and amperage rating down any one contact.
28
What components should be connected to the contactor?
Coils, Field wiring, Contacts, Control wiring.
29
What is the purpose of the hypothetical circuit described?
To run a cooling fan for a large room that automatically kicks on when the room temperature reaches a certain degree.
30
What voltage transformation is mentioned for the control circuit?
Transforming 380VAC to 120VAC.
31
What should be referred to for selecting devices in the circuit?
Week #3 reference materials.
32
What should be read in chapter 5, pages 71 to 75?
Different styles and types of contactors, coil ratings, voltage ratings, and availability of NO or NC contacts.
33
What types of contactors can be obtained?
Single pole up to even a 12 pole contactor.
34
What type of contactor should be selected?
The type of contactor depends on the specific application requirements.
35
What is the purpose of a Photo Cell?
The purpose of a Photo Cell is to automatically sense light levels and control lighting accordingly.
36
Is a Photo Cell an automatic sensing device?
Yes, a Photo Cell is an automatic sensing device.
37
How does a Photo Cell work?
A Photo Cell works by detecting ambient light levels and activating or deactivating lighting systems based on those levels.
38
Is a Photo Cell found in the control circuit or the branch circuit?
A Photo Cell is typically found in the control circuit.
39
How many physical components are there to the Photo Cell, and what are they called?
There are typically two physical components to the Photo Cell: the sensor and the relay.
40
What is the voltage required for the sensor, and what is the maximum ampacity that can flow through it?
The voltage required for the sensor varies, but it commonly operates at 120V, with a maximum ampacity of typically 10 amps.
41
Could I run 10 lights through the PC sensor if they each used 1 amp?
No, you could not run 10 lights through the PC sensor if they each used 1 amp, as that would total 10 amps, which exceeds the typical maximum ampacity.
42
What is the name of the device shown in the photo above and what is the abbreviation for this device?
Control relay, CR.
43
How many physical components are there to a control relay, and what are their names?
2, relay base and relay 'cube'.
44
Can relay cubes come in more than an 8 pin configuration, if so name the pin configuration shown above?
Yes, we also have an 11 pin.
45
Are relay bases used for control relays only, or is the base a standard template that can be used for other electrical devices?
Can be used for other electrical devices.
46
Where would you find electrical rating information for the relays and relay bases?
It would be located in the manufacturer's specification sheets.
47
How many internal components are there in a relay, or commonly referred to as a relay base? What is the name of the internal components?
2, the coil and the contacts.
48
What is the most important difference between the 2 relays shown in the photos on the right above?
They have different coil voltages.
49
If you supply the incorrect voltage to your relay coil, and it works momentarily, then fails to work again, and you see a smoky discolouration on the cube, smell melting copper, and once you lock out and remove protective covers and feel residual heat in the relay. Did you apply an over voltage or an under voltage?
Over Voltage.
50
If you apply the incorrect voltage to your relay coil, and it makes a humming noise, and does not actuate. Did you apply an over voltage or an under voltage?
Under Voltage.
51
If you apply an over voltage to any coil, and after a period of time you see smoke, and or smell burning, will that coil ever work again?
No.
52
What is the word electricians use to describe the noise that is made by an electrical device that has an under voltage, or failing coils?
Chattering.
53
What is the purpose of the red button shown on the relays?
They are the manual actuation buttons.
54
How many sets of contacts are there in an 8-pin relay?
2
55
What does a set of contacts consist of?
1 common termination point and 1 NC, and 1 NC.
56
What are the termination #s required for a NC contact on the left side of the relay?
Refer to the specific wiring diagram for exact termination numbers.
57
What are the termination #s required for a NO contact on the left side of the relay?
Refer to the specific wiring diagram for exact termination numbers.
58
What are the termination #s required for a NC contact on the right side of the relay?
Refer to the specific wiring diagram for exact termination numbers.
59
What are the termination #s required for a NO contact on the right side of the relay?
Refer to the specific wiring diagram for exact termination numbers.
60
How many sets of contacts does an 11-pin control relay have?
3
61
What should the resistance of the 24 Vac coil for an 8-pin relay be?
75 ohms ± 15%
62
What should the resistance be for a 110 Vac coil in an 8 pin relay?
1700 ohms ± 15%
63
What current does the 24Vac relay coil use?
0.32 A
64
What current does the 120 Vac relay coil use?
0.07 A
65
What is the best way to isolate which circuit the issue is in for a contactor or control relay?
Manually actuate the relay or contactor. If the motor runs, the issue is in the control circuit; if it does not, it is more likely in the field wiring.
66
Why take a different approach when commissioning a new motor circuit compared to a system that has failed?
A system that has failed has verified that the wiring was routed correctly; a new system has not been proven to be wired correctly.
67
Is manually actuating the device while the circuit is energized and the electrical cover is removed considered energized work?
No
68
Is manually actuating the device while the circuit is energized and the electrical cover is removed exposing energized components considered energized work?
Yes, you have passed the limited and restricted approach boundaries.
69
Should you follow company procedures and wear prescribed PPE when working on a circuit system that has failed?
Yes, it will eliminate half of the work and may even find the problem in the process.
70
How can you verify that all contacts and the base of a relay are functioning properly at a zero energy state?
Set your meter to continuity, put leads on either end of the NO or NC contacts, manually actuate. If the contacts change state (e.g., from NO to NOHC), then they are working.
71
How long would it take to verify a relay or contactor prior to installing it out of the box?
Once you are competent, under 30 seconds.
72
How long could it take to find and replace a defective device in a complex circuit?
It could take hours.
73
Does it make sense to verify correct device function prior to installations?
Yes.
74
How can we verify if the coils on devices are in good working order without energization?
We could measure the resistance of the coil and compare it to the manufacturer's specification.
75
What happens if you energize a coil with resistance much lower than the specified range?
It would dead short.
76
What is the device number to search for specifications and installation sheets?
8910DPA33V02.
77
How long did it take to find and download the spec sheet for the device?
Under 30 seconds.
78
What is the listed coil resistance for the 8910DPA33V02?
Not sure, it was not listed.
79
What are the three things you can do if technical information for a device is not listed?
1. Compare coil resistance with multiple devices of the same type. 2. De-energize and disconnect the suspected defective device and compare resistance to a new device. 3. Call or e-mail for technical support.
80
What is the resistance for the coil on the contactor that actuates properly?
182.1 Ohms.
81
What should you do in lab class regarding your contactor's coil resistance?
Measure your contactor's coil resistance with permission from your instructor.
82
What was the challenge faced by electricians before the availability of technological access to specifications?
It was next to impossible to find information such as device specification sheets.
83
What change will modern electricians be able to create in troubleshooting practices?
Safer troubleshooting practices.
84
What ability will modern electricians have regarding coil resistances?
They will be able to compare known resistances for most coils.
85
Is it likely that perfectly good devices are replaced and discarded because electricians are not aware how to confirm functionality?
Yes
86
Will the problem still exist if the device was not the issue?
Yes
87
Did you just waste time, money, resources, and increase the downtime of working machinery?
Yes
88
Is it reasonable to see why electricians that were not trained in this era of technology struggle to adapt?
Yes
89
What is a magnetic relay basically?
A solenoid (magnet) with movable contacts
90
What type of relays are the ones you use in class shown in the photos above?
Single pole double throw clapper type relays
91
What type of contactor do we use in class?
Bridge type contactor
92
Core losses caused by induced voltage into the core materials causing current to swirl around causing heat are called?
Eddie currents
93
What is hysteresis loss caused by?
The continual changing of magnetic polarity from an AC circuit
94
What is the purpose of a Shading coil?
They are used to prevent chattering.
95
A relay that does not use mechanical contacts to connect the line to the load is known as what type of relay?
A solid State
96
What is the greatest difference between relays and contactors?
Contactors can handle more load.
97
Another name for mechanically held contacts or relays is?
Latching
98
What is a device that has a physical set point, and when the ambient temperature drops below set point it closes a set of contacts allowing current to flow?
Heating thermostat
99
How many poles are there on the temperature switch shown in the week#3 reference materials?
1
100
Would this be a NOHC or a NCHO?
Depends on the room temperature and the set point.
101
What is the difference between a heating thermostat and a cooling thermostat regarding contacts closing based on ambient temperature?
Cooling contacts close when the temperature rises, heating contacts close when the temperature falls.
102
Regardless of heating or cooling, how do we draw the temperature switch NO on our drawings?
Please draw the NEC symbol for our temperature switch.
103
What is the voltage and amperage rating for the thermostat in the photo?
22A and 240Vac.
104
If you are using a single pole thermostat for 240Vac, what is the most dangerous thing that electricians need to be aware of?
Single pole T-stats only close one phase of the 240, so 120VAC can still be present at the equipment that the T-stat controls.

MOTOR CONTROL FUNDAMENTALS (6 decks)

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