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Electrical > Motors > Flashcards

Motors Flashcards

1
Q

What are the three types of single phase motors

A

-Shaded-pole induction motors
-universal motors
- split-phase induction motors

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2
Q

What are the 4 types of split-phase induction motors

A

-Resistance -start induction-run RSIR
-Capacitor-start Induction-run CSIR
- Permanent-split capacitor PSC
-Capacitor-start capacitor-run CSCR

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3
Q

Shaded-pole induction motor: uses

A

small fans, clocks, toys

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4
Q

Shaded-pole induction motor: Torque

A

Lowest starting torque and running torque of all motors

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5
Q

Shaded-pole induction motor: Speed

A

Constant fixed speed

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6
Q

Shaded-pole induction motor: Starting

A

No starting winding or centrifugal switch

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7
Q

Shaded-pole induction motor: Reverse

A

Mechanically remove stator winding and turn it around end for end

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8
Q

Universal series motor: uses

A

power tools, vacuums

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9
Q

Universal series motor: Torque

A

High starting torque

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10
Q

Universal series motor: Speed

A

Good speed control, but poor speed regulation

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11
Q

Universal series motor: Starting

A

Self-starting

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12
Q

Universal series motor: Reverse

A

Interchange armature leads A1 and A2

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13
Q

Resistance-start induction-run (split-phase): uses

A

washing machine, dish washer

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14
Q

Resistance-start induction-run (split-phase): Torque

A

Poor starting torque, poor running torque

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15
Q

Resistance-start induction-run ( split-phase): Speed

A

Constant fixed speed

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16
Q

Resistance-start induction-run (split-phase): Reverse

A

Interchange start winding leads T5 and T8

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17
Q

Resistance-start induction-run (split-phase): Start winding - Run winding

A

The start winding is made with more turn of smaller gauge wire

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18
Q

Capacitor-start induction-run: uses

A

Refrigerators, freezers

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19
Q

Capacitor-start induction-run: Torque

A

High starting torque, poor running torque

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20
Q

Capacitor-start induction-run: Speed

A

Constant fixed speed

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21
Q

Capacitor-start induction-run: Starting

A

Requires disconnecting means for start winding and capacitor

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22
Q

Resistance-start induction-run (split-phase): Starting:

A

Requires disconnecting means for start winding

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23
Q

Capacitor-start induction-run: Reverse

A

Interchange start winding leads T5 and T8

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24
Q

Capacitor-start induction-run: Start winding - Run winding

A

The start winding is made with more turns of smaller gauge wire

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25
Q

Permanent split-capacitor (capacitor-start and run): uses

A

Central air-conditioners, blowers

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26
Q

Permanent split-capacitor (capacitor-start and run): Torque

A

Good starting torque and good running torque

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27
Q

Permanent split-capacitor _capacitor-start and run): Speed

A

Constant Fixed speed

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28
Q

Permanent split-capacitor (capacitor-start and run): Starting

A

No disconnecting means, start winding remains energized

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29
Q

Permanent split-capacitor (capacitor-start and run): Reverse

A

Start winding leads T5 and T8

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30
Q

Permanent split-capacitor (capacitor-start and run): Start winding - run winding

A

The start winding is equal to or much closer to the run winding

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31
Q

What are the methods of disconnecting Single-phase start windings? (5)

A
  • centrifugal switch
    -hot-wire relay
    -current relay
  • potential relay
  • Thermistor
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32
Q

Types of three phase motors (3)

A

-Squirrel-cage
-Wound-rotor
-Synchronous

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33
Q

Squirrel-cage induction motor: uses

A

Fans, pumps, machines

34
Q

Squirrel-cage induction motor: Torque

A

Starting torque is 100% to 275% full-load torque

35
Q

Squirrel-cage induction motor: Speed

A

Good speed control with good speed regulation

36
Q

Squirrel-cage induction motor: Starting

A

Self-starting

37
Q

Squirrel-cage induction motor: Reverse

A

Interchange L1 and L3

38
Q

Squirrel-cage induction motor: Advantages

A
  • the rotor uses embedded rotor bars
    -no commutator or slip rings to service
  • no brushes to replace or maintain
  • as the load increases, both the power factor and torque improves
39
Q

Wound-Rotor induction motor: uses

A

Crane hoists, elevators

40
Q

Wound-Rotor induction motor: Torque

A

Excellent starting torque and good speed regulation

41
Q

Wound-Rotor induction motor: Speed

A

Excellent speed control with good speed regulation

42
Q

Wound-Rotor induction motor: Reverse

A

Interchange L1 and L3

43
Q

Wound-Rotor induction motor: advantages

A
  • improved power factor as the load increases
    -smooth acceleration
    -works well on high inertia loads
44
Q

Wound-Rotor induction motor: Disadvantages

A
  • Does not maintain high efficiency at low speeds
    -Relies on external speed controller to minimize inductive reactance
45
Q

Dc Motors: uses

A

Trains, Hoists

46
Q

Dc Motors: Torque

A

Excellent starting torque and excellent running torque

47
Q

Dc Motors: Speed

A

Excellent speed control with excellent speed regulation

48
Q

Dc Motors: Starting

A

Self-starting

49
Q

Dc Motors: Reverse

A

Interchange A1 and A2

50
Q

Dc Motors: Series winding

A

Made with few turns of larger wire, S1 and S2

51
Q

Dc Motors: Shunt winding

A

Made with many turns of smaller wire, F1 and F2

52
Q

Three types of DC Motors

A

Series, Shunt, Compound

53
Q

Synchronous Motor: uses

A

power factor correction

54
Q

Synchronous Motor: Torque

A

Good starting torque

55
Q

Synchronous Motor: Speed

A

Constant speed from no-load to full-load

56
Q

Synchronous Motor: Reverse

A

Interchange L1 and L3

57
Q

Synchronous Motor: Starting

A

Self-starting by means of armortisseur winding

58
Q

How many slip rings in each three phase motor?

A

Synchronous- 2
Wound-Rotor- 3
Squirrel Cage- 0

59
Q

What are the three types of braking?

A

-Mechanical brakes
-Dynamic braking
-Plugging

60
Q

Mechanical brakes:

A

Converts kinetic energy of load to thermal energy when motor is stopped, can hold suspended load

61
Q

Dynamic braking:

A

Uses magnetic field to slow motor rotation, cannot hold suspended load, no brake shoes to wear out

62
Q

What is the principle of dynamic braking for DC?

A

To change motor into a generator

63
Q

Plugging:

A

A system of braking in which the motor connections are reversed so that the motor develops a counter torque that acts as a retarding force

64
Q

What happens in a three-phase motor in the event of single phasing?

A

Excessive current and possibly burnt windings

65
Q

What is the single biggest advantage of a wound-rotor motor?

A

-Speed control

66
Q

If one disconnects the windings of a wound-rotor motor from the resistors, and shorts them together, what happens when power is applied to the stator?

A

High inrush current due to smaller resistance windings

67
Q

The winding that simulates a squirrel-cage in a synchronous motor is the ____ winding

A

Amortisseur winding

68
Q

The power factor of a three-phase, squirrel-cage induction motor operating with full load…

A

improves from no load

69
Q

The speed of a squirrel-cage induction motor depends on:

A

frequency and number of poles

70
Q

The rotating part of an AC motor is the:

A

Rotor

71
Q

Who or what determines if large induction motors may be started at full voltage across the line?

A

The power company

72
Q

The power factor of a three-phase, squirrel-cage induction motor operating unloaded is:

A

very poor

73
Q

The squirrel-cage induction motor is popular because of its characteristics of:

A

Simple, rugged construction

74
Q

Some motors are constructed so that they will operate on either of two voltages. when they are connected to operate on the lower of the two voltages, the windings are connected in:

A

Parallel

75
Q

The speed of an Ac induction motor depends on the line frequency and the:

A

of stator poles

76
Q

The speed of a wound-rotor motor is decreased by

A

inserting resistance into the secondary circuit

77
Q

A synchronous motor with an under excited dc field has:

A

A lagging power factor

78
Q

What would cause an electrical contractor to take on a blue discoloration?

A

High temperatures

79
Q

What must be done immediately after a Hi-pot test?

A

Ground the equipment

80
Q

If the centrifugal switch in a split phase motor is stuck open, then the motor will:

A

Not start

Electrical (13 decks)

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