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Motor Control > T1 > Flashcards

T1 Flashcards

1
Q

What is GFCI device and what does it do?

A

ground-fault circuit breaker. Protects devices from power surges.

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2
Q

What is grounding?

A

Grounding provides a low resistance path to ground to prevent conductive objects from existing at a high potential.

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3
Q

What is a soft start?

A

Bringing the motor up to speed over a period of time instead of all at once. Used for flywheels and centrifuges.

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4
Q

What is jogging a motor?

A

Starting a motor with short jabs of power at full voltage.

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5
Q

What is inching a motor?

A

Starting a motor with short jabs of power at a reduced voltage.

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6
Q

What are manual controllers?

A

Simple devices that connect the motor directly to the line

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7
Q

What is semiautomatic control?

A

Using pushbuttons, limit switches, pressure switches and other sensing devices to control the operation of a magnetic contactor or starter.

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8
Q

What is a schematic diagram?

A

Shows components in their electrical sequence without regard for physical location.

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9
Q

What is a wiring diagram?

A

A pictorial representation of the control components with connecting wires.

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10
Q

What is across the line starting?

A

Connecting the motor directly to the power line

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11
Q

What is ramping?

A

Starting the motor at a low speed and accelerating to full speed ober a period of time.

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12
Q

What is leakage current?

A

The current flow through the MOV (Metal Oxide Varistor)

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13
Q

What are diodes used for?

A

Used to supress the voltage spikes produced by coils that operate on direct current.

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14
Q

How are diodes connected?

A

Reverse bias to the voltage connected to the coil.

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15
Q

T or F: Schematics are always drawn to show components in their de-energized or off state.

A

T

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16
Q

T or F: Any contact that has the same label or number as a coil is controlled by that coil.

A

T

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17
Q

What is on a data plate

A
  1. HP of a motor
  2. Service factor
  3. Full load amp
  4. Frame
  5. Temperature rise
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18
Q

Stopping a motor

A
  1. Coast
  2. Plug
  3. Brake
  4. Dynamic braking
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19
Q

Protecting from spikes DC

A

MOV or diode

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20
Q

Protecting from spikes AC

A

Zeiner diode or MOV

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21
Q

Manual starters advantage

A

Will restart under power failure

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22
Q

Manual starters disadvantage

A

Will restart under power failure

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23
Q

Dont do what for isolation

A

Dont use a set of contacts

24
Q

3 things for overload properties

A
  1. Must have the ability to sense current
  2. A current sensing section and a contact section
  3. Time delay
25
Dashpots use what kind of oil
Dash pot oil
26
2 types of overload relays
1. Thermal: Solder melting, bimetallic 2. Magnetic: electronic, dashpot
27
What are overload contacts
In series with the coil and not made to take high current
28
What are AC coils
Laminated to reduce eddy currents. Uses shading coils to prevent chattering
29
How do springs or gravity affect contacts
Re-opens contacts
30
2 types of core losses in a transformer
1. Eddy currents 2. Hysterisis/ Molecular friction
31
Relay that has a coil on the input
REED relay
32
Relay that has an LED on the input
LED Relay
33
What device is used on the output of a solid state relay when its used for DC
Transistor
34
What device is used on the output of a solid state relay when its used for AC
Triac
35
Load contacts do what
Connects to the main load
36
Control contact do what
Used in control circuits
37
Ways to extinguish an arc
1. Arc shute 2. Arc horn 3. Blowout coil 4. Bellows 5. Vacuum contactors
38
What relays should you never use
Mercury relays
39
5 different types of transformers
1. Power transformers 2. Distribution transformers 3. Control transformer 4. Current transformer 5. Potential transformer
40
What is a grounded system
The secondary of the transformer is grounded
41
If the secondary of a transformer is not grounded it is typically referred to as a what system
Floating system
42
3 ways to fuse a transformer
1. Primary 2. Secondary 3. Both
43
Stop buttons are put in ______ with the coil
Series
44
Start buttons are put in ______ with the coil
Parallel
45
How is the rotation of a three phase motor reversed
Changing two of the three phases
46
Interlocking techniques
1. Mechanical 2. Push button 3. Contacts
47
What determines the amount of warp for a bimetal strip
1. Metal used 2. Difference in temperature between the two ends 3. Length of strip
48
What is a motor starter composed of
Contactor and overload
49
What does the element in a fuse measure
Temperature
50
How do you avoid corse losses
Laminating the core
51
What does laminating a core do?
Helps reduce the formation of eddy currents
52
Relays compared to contactors
Relays can only be used for 10 Amps or lower
53
Load contacts are intended to be used for what
High voltage from power sources
54
What are load contacts intended for?
Used to connect the load to the power supply
55
What is a combination starter
A starter and an isolation switch or breaker combined
56
What are the two methods of electrical interlocking
1.Double acting push buttons 2.Electrical interlocking (connecting the normally closed auxillary contacts on one contactor in series with the coil of the other contactor)
57
What is interlocking
Prevents some action from taking place until some other action has been performed

Motor Control (2 decks)

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