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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
Q

Dashpots use what kind of oil

A

Dash pot oil

26
Q

2 types of overload relays

A
  1. Thermal: Solder melting, bimetallic
  2. Magnetic: electronic, dashpot
27
Q

What are overload contacts

A

In series with the coil and not made to take high current

28
Q

What are AC coils

A

Laminated to reduce eddy currents. Uses shading coils to prevent chattering

29
Q

How do springs or gravity affect contacts

A

Re-opens contacts

30
Q

2 types of core losses in a transformer

A
  1. Eddy currents
  2. Hysterisis/ Molecular friction
31
Q

Relay that has a coil on the input

A

REED relay

32
Q

Relay that has an LED on the input

A

LED Relay

33
Q

What device is used on the output of a solid state relay when its used for DC

A

Transistor

34
Q

What device is used on the output of a solid state relay when its used for AC

A

Triac

35
Q

Load contacts do what

A

Connects to the main load

36
Q

Control contact do what

A

Used in control circuits

37
Q

Ways to extinguish an arc

A
  1. Arc shute
  2. Arc horn
  3. Blowout coil
  4. Bellows
  5. Vacuum contactors
38
Q

What relays should you never use

A

Mercury relays

39
Q

5 different types of transformers

A
  1. Power transformers
  2. Distribution transformers
  3. Control transformer
  4. Current transformer
  5. Potential transformer
40
Q

What is a grounded system

A

The secondary of the transformer is grounded

41
Q

If the secondary of a transformer is not grounded it is typically referred to as a what system

A

Floating system

42
Q

3 ways to fuse a transformer

A
  1. Primary
  2. Secondary
  3. Both
43
Q

Stop buttons are put in ______ with the coil

A

Series

44
Q

Start buttons are put in ______ with the coil

A

Parallel

45
Q

How is the rotation of a three phase motor reversed

A

Changing two of the three phases

46
Q

Interlocking techniques

A
  1. Mechanical
  2. Push button
  3. Contacts
47
Q

What determines the amount of warp for a bimetal strip

A
  1. Metal used
  2. Difference in temperature between the two ends
  3. Length of strip
48
Q

What is a motor starter composed of

A

Contactor and overload

49
Q

What does the element in a fuse measure

A

Temperature

50
Q

How do you avoid corse losses

A

Laminating the core

51
Q

What does laminating a core do?

A

Helps reduce the formation of eddy currents

52
Q

Relays compared to contactors

A

Relays can only be used for 10 Amps or lower

53
Q

Load contacts are intended to be used for what

A

High voltage from power sources

54
Q

What are load contacts intended for?

A

Used to connect the load to the power supply

55
Q

What is a combination starter

A

A starter and an isolation switch or breaker combined

56
Q

What are the two methods of electrical interlocking

A

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
Q

What is interlocking

A

Prevents some action from taking place until some other action has been performed

Motor Control (2 decks)

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