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MOTOR CONTROL FUNDAMENTALS > WORKSHEET #5 > Flashcards

WORKSHEET #5 Flashcards

1
Q

What is a current limiting device, or commonly referred to as an overcurrent device?

A
  1. Protects electrical circuits from excessive current.
  2. Automatically interrupts the circuit when a fault occurs.
  3. Helps prevent damage to equipment and wiring.
  4. Can be reset or replaced after a fault.
  5. Essential for safety in electrical systems.
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2
Q

What are the 2 main types of Overcurrent devices we use?

A
  1. Circuit breakers.
  2. Fuses.
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3
Q

What type of breaker would I use for single phase 240VAC?

A

I would use a 2-pole breaker.

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4
Q

What type of breaker would I use for single phase 120VAC?

A

I would use a 1-pole breaker.

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5
Q

What type of breaker would I use for 208VAC?

A

I would use a 2-pole breaker.

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6
Q

What type of breaker would I use for three phase 120VAC?

A

I would use a 3-pole breaker.

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7
Q

What type of breaker would I use for three phase 208VAC?

A

I would use a 3-pole breaker.

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8
Q

What are the two main types of fuses used in industry?

A
  1. Cartridge fuses.
  2. Plug fuses.
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9
Q

What is the purpose of an overcurrent device?

A

Overcurrent device is intended to protect electrical circuits from damage due to excessive current.

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10
Q

What is Section 28 specific to?

A

Section 28 is specific to branch circuit overcurrent protection.

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11
Q

What does 28-200 refer to?

A

It refers to branch circuits that feed specific loads.

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12
Q

Which sections apply to wiring Motors?

A

Sections 14 and 28 code rules apply.

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13
Q

How does the code book condense the number of pages?

A

It shares the same electrical codes between Section 14 and 28.

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14
Q

What does Table 29 specify?

A

It specifies the rating or setting of overcurrent devices that protect conductors.

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15
Q

What are the allowed percentages for overcurrent devices?

A

For a Time delay fuse, allowed to go 125%; for a Non-time Delay, 100%; for a circuit breaker, 250% larger than Full Load Amps (FLA).

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16
Q

Why do we need large overcurrent devices for motor circuits?

A

Motor circuits require larger overcurrent devices due to inrush current and operational demands.

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17
Q

How do you size a conductor for a single phase AC motor?

A

Multiply the FLA of the motor by 125% to find the lowest allowable ampacity.

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18
Q

What is the FLA for a motor with 10A?

A

For a motor with an FLA of 10A, use #14 AWG copper conductors @ 75 degrees.

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19
Q

What is the allowed breaker size for the motor?

A

The breaker is allowed to be 25 amps according to Table 29.

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20
Q

How can we allow a larger overcurrent device than the conductor can handle?

A

Overcurrent protection is intended to protect the wires, but larger devices accommodate inrush currents.

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21
Q

What is FLA?

A

FLA stands for Full Load Amps.

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22
Q

What happens to a motor’s FLA under a demanding workload?

A

The FLA increases when exposed to a more demanding workload.

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23
Q

What could happen if a motor uses 20% more ampacity than designed?

A

The motor or wires could overheat or fail due to excessive current.

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24
Q

List 3 things that could cause a motor to be overworked?

A
  1. Excessive load on the motor.
  2. Insufficient power supply.
  3. Mechanical binding or friction.
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25
What is the principle of an overload device?
An overload device operates by interrupting the circuit when the current exceeds a predetermined level.
26
If overcurrent devices are designed to protect the conductors, then what are overload devices designed to protect?
Overload devices are designed to protect the motor from overheating.
27
Is overload protection required by CEC?
Yes, overload protection is required by the Canadian Electrical Code (CEC).
28
What is the basic function of an overload relay?
The basic function of an overload relay is to disconnect the motor from the power supply in case of an overload condition.
29
What are the 2 methods used by physical overload relays to measure current?
1. Bimetallic strip method. 2. Current transformer method.
30
Overloads need to have a small delay before actuating, why is this?
The delay allows for temporary current spikes without tripping the relay.
31
What are the 2 different physical sections that overload relays are divided up into?
1. Sensing section. 2. Control section.
32
Duel element fuses protect against what two things?
1. Overcurrent. 2. Short circuits.
33
What are the 2 types of thermal overloads?
1. Bimetallic thermal overloads. 2. Electronic thermal overloads.
34
What type of overload uses an overload heater as the current sensing device?
A device that uses an overload heater that holds a spring down to close a set of contacts in the control circuit under normal conditions. ## Footnote When conditions are not normal, the overload heater heats up, causing a metal to melt and release the spring, opening the control circuit contacts.
35
What type of overload uses the warping of different metals when heat is applied?
An overload relay that forces a set of contacts open in the control circuit due to the warping of metals. ## Footnote This action opens the field wiring contactor.
36
What type of overload uses lines of flux generated by current flowing through conductors?
An overload relay that opens a set of contacts in the control circuit when excessive flux occurs, shutting off the motor. ## Footnote This type of overload is known as a magnetic overload.
37
What is the abbreviation that we use for the word overload?
OL
38
Which type of overload has no adjustment?
The overload relay that uses lines of flux.
39
Which type of overload does not use heat?
The overload relay that uses lines of flux.
40
What are the 2 different types of Magnetic relays?
1. Electromagnetic relay 2. Solid-state relay
41
What are the 3 main factors that allow a Dashpot relay to function?
1. Fluid viscosity 2. Piston movement 3. Time delay
42
How many OL contacts are required for a single phase motor?
1 OL contact
43
How many OL contacts are required for a 3 phase motor?
3 OL contacts
44
What state are OL contacts for the control circuit typically in?
Closed state
45
What are the additional sets of contacts in OL Relays typically referred to as?
Additional sets of contacts are typically referred to as auxiliary contacts.
46
How do we know what size of overload to use?
We determine the size of overload based on specific criteria and calculations.
47
In your words what is a disconnect?
A disconnect is a device that separates a motor from its power source.
48
Are we required by the CEC to have a Disconnect for any motor installed?
Yes, the CEC requires a disconnect for any installed motor.
49
List 3 motors in your home that have a disconnect, and in what form is the disconnect?
1. Air conditioner - circuit breaker 2. Refrigerator - plug 3. Washer - wall switch
50
Is it ok to use a 15A light switch or a 15A receptacle as a disconnect means for any and all motors?
No, a 15A light switch or receptacle is not suitable for all motors.
51
For motors larger than ¾ HP, what type of disconnect does CEC require us to use?
CEC requires a manual motor starter for motors larger than ¾ HP.
52
What is the name given to manual disconnects that serve motors larger than 3/4HP, and according to CEC, can they be as a disconnect means?
They are called Manual Motor Starters (MMS) and can be used as a disconnect means.
53
What is the abbreviation that we will use for Manual motor Starters?
The abbreviation is MMS.
54
A device that resembles a light switch, that is configured to accept an OL, for a motor of less than 1 HP, is known as what?
It is known as a Manual Motor Starter (MMS).
55
How many poles (contacts) are required for a MMS that is designed to disconnect 120VAC?
Two poles (contacts) are required for 120VAC.
56
How many poles (contacts) are required for a MMS that is designed to disconnect 240VAC single phase motors?
Two poles (contacts) are required for 240VAC single phase motors.
57
How many poles (contacts) are required for a MMS that is designed to disconnect 208VAC three phase motors?
Three poles (contacts) are required for 208VAC three phase motors.
58
Name three different styles or designs of MMS based on physical location, that the book has listed?
1. Wall-mounted 2. Panel-mounted 3. Portable
59
Can MMS come with push button control instead of a toggle switch?
Yes, MMS can come with push button control.
60
Do MMS require a control circuit?
Yes, MMS require a control circuit.
61
Do MMS require a contactor with a coil?
No, MMS do not require a contactor with a coil.
62
Why is monitoring the fixed Motor circuit so important?
Monitoring the fixed Motor circuit is crucial for ensuring safety and operational efficiency.
63
What type of device is required in a Motor starter with automatic energization?
An automatic device is required in the starter.
64
In figure 5-39, which half of the Automatic starter is the contactor portion?
The top half of the Automatic starter is the contactor portion.
65
Is the OL on the starter in figure 5-39 Thermal or Magnetic?
The OL on this starter is Thermal.
66
What is the clear plastic section of the starter in figure 5-44 known as?
The clear plastic section is known as the cover.
67
What is the function of the red plastic piece in figure 5-44?
The red plastic piece serves as a safety indicator.
68
Name all 5 electrical components shown in figure 5-46 of the combinations starter.
The components are the contactor, overload relay, circuit breaker, control transformer, and auxiliary contacts.
69
What is a MCC?
A MCC (Motor Control Center) is a centralized location for controlling electric motors.
70
What is the purpose of a MCC?
The purpose of a MCC is to provide motor control and protection in an organized manner.

MOTOR CONTROL FUNDAMENTALS (6 decks)

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