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Motors Flashcards

(80 cards)

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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
Permanent split-capacitor (capacitor-start and run): uses
Central air-conditioners, blowers
26
Permanent split-capacitor (capacitor-start and run): Torque
Good starting torque and good running torque
27
Permanent split-capacitor _capacitor-start and run): Speed
Constant Fixed speed
28
Permanent split-capacitor (capacitor-start and run): Starting
No disconnecting means, start winding remains energized
29
Permanent split-capacitor (capacitor-start and run): Reverse
Start winding leads T5 and T8
30
Permanent split-capacitor (capacitor-start and run): Start winding - run winding
The start winding is equal to or much closer to the run winding
31
What are the methods of disconnecting Single-phase start windings? (5)
- centrifugal switch -hot-wire relay -current relay - potential relay - Thermistor
32
Types of three phase motors (3)
-Squirrel-cage -Wound-rotor -Synchronous
33
Squirrel-cage induction motor: uses
Fans, pumps, machines
34
Squirrel-cage induction motor: Torque
Starting torque is 100% to 275% full-load torque
35
Squirrel-cage induction motor: Speed
Good speed control with good speed regulation
36
Squirrel-cage induction motor: Starting
Self-starting
37
Squirrel-cage induction motor: Reverse
Interchange L1 and L3
38
Squirrel-cage induction motor: Advantages
- 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
Wound-Rotor induction motor: uses
Crane hoists, elevators
40
Wound-Rotor induction motor: Torque
Excellent starting torque and good speed regulation
41
Wound-Rotor induction motor: Speed
Excellent speed control with good speed regulation
42
Wound-Rotor induction motor: Reverse
Interchange L1 and L3
43
Wound-Rotor induction motor: advantages
- improved power factor as the load increases -smooth acceleration -works well on high inertia loads
44
Wound-Rotor induction motor: Disadvantages
- Does not maintain high efficiency at low speeds -Relies on external speed controller to minimize inductive reactance
45
Dc Motors: uses
Trains, Hoists
46
Dc Motors: Torque
Excellent starting torque and excellent running torque
47
Dc Motors: Speed
Excellent speed control with excellent speed regulation
48
Dc Motors: Starting
Self-starting
49
Dc Motors: Reverse
Interchange A1 and A2
50
Dc Motors: Series winding
Made with few turns of larger wire, S1 and S2
51
Dc Motors: Shunt winding
Made with many turns of smaller wire, F1 and F2
52
Three types of DC Motors
Series, Shunt, Compound
53
Synchronous Motor: uses
power factor correction
54
Synchronous Motor: Torque
Good starting torque
55
Synchronous Motor: Speed
Constant speed from no-load to full-load
56
Synchronous Motor: Reverse
Interchange L1 and L3
57
Synchronous Motor: Starting
Self-starting by means of armortisseur winding
58
How many slip rings in each three phase motor?
Synchronous- 2 Wound-Rotor- 3 Squirrel Cage- 0
59
What are the three types of braking?
-Mechanical brakes -Dynamic braking -Plugging
60
Mechanical brakes:
Converts kinetic energy of load to thermal energy when motor is stopped, can hold suspended load
61
Dynamic braking:
Uses magnetic field to slow motor rotation, cannot hold suspended load, no brake shoes to wear out
62
What is the principle of dynamic braking for DC?
To change motor into a generator
63
Plugging:
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
What happens in a three-phase motor in the event of single phasing?
Excessive current and possibly burnt windings
65
What is the single biggest advantage of a wound-rotor motor?
-Speed control
66
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?
High inrush current due to smaller resistance windings
67
The winding that simulates a squirrel-cage in a synchronous motor is the ____ winding
Amortisseur winding
68
The power factor of a three-phase, squirrel-cage induction motor operating with full load...
improves from no load
69
The speed of a squirrel-cage induction motor depends on:
frequency and number of poles
70
The rotating part of an AC motor is the:
Rotor
71
Who or what determines if large induction motors may be started at full voltage across the line?
The power company
72
The power factor of a three-phase, squirrel-cage induction motor operating unloaded is:
very poor
73
The squirrel-cage induction motor is popular because of its characteristics of:
Simple, rugged construction
74
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:
Parallel
75
The speed of an Ac induction motor depends on the line frequency and the:
of stator poles
76
The speed of a wound-rotor motor is decreased by
inserting resistance into the secondary circuit
77
A synchronous motor with an under excited dc field has:
A lagging power factor
78
What would cause an electrical contractor to take on a blue discoloration?
High temperatures
79
What must be done immediately after a Hi-pot test?
Ground the equipment
80
If the centrifugal switch in a split phase motor is stuck open, then the motor will:
Not start

Electrical (13 decks)

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