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A/B Flashcards

(56 cards)

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1
Q

Motors function

A

Device that converts electrical power (energy) into mechanical power (energy)

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2
Q

What is an Inducting motor?

A

A machine that gets energy into the rotating part by mutual induction

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3
Q

Define Torque

A

Moment of force

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4
Q

Prony brake

A

Measures a motors torque.
More sophisticated alternate is a dynometer

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5
Q

Unit of measurement for torque

A

Newton meters - (Nm)

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6
Q

Torque formula

A

T = F X r
F - force in newtons (N)
r - radius in meters (m)

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7
Q

What is Efficiency?

A

The ratio of output energy (power) over input energy (power)

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8
Q

Induction motors 3 parts

A

Frame (enclosure)
Stator
Rotor

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9
Q

Induction motor frame includes

A

Cast steel frame
End brackets (frame)
Bearings in the end brackets
Junction box

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10
Q

Drip proof motors allow outside air too

A

-Enter one end of the motor

-Flow past the stator windings

-Flow between the stator and windings

-Exit the other end

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11
Q

3 Types of totally enclosed motors

A

Fan cooled (tefc)

Non ventilated (tenb)

Pipe ventilated (tepv)

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12
Q

Stator is comprised of?

A

stationary iron and winding

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13
Q

Stator core is constructed of

A

Thin silicon steel laminations to minimize Eddie current and hysteresis

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14
Q

Two types of Stator windings are

A

Lap windings

Concentric windings

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15
Q

Define a Rotor

A

Rotating part of an electrical machine is called a rotor.

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16
Q

What are 2 types of rotors

A

Squirel cage rotors and wound rotors

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17
Q

Squirrel cage rotors consist of

A

Aluminum or copper bars called rotor conductors or rotor bars

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18
Q

Slip speed

A

Difference between rotor speed and the synchronized speed of the stators magnetic speed

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19
Q

Wound rotor motor is identical to what?

A

The stator is identical to a SCIM stator.

wound rotor motors are less common than the squirrel cage because it needs more maintenance

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20
Q

What is the Slip speed %

A

Typically 2 - 5% of synchronized speed

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21
Q

Parts of a Rotors includes

A

laminated iron conductors and the shaft

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22
Q

Losses in an induction motor

A

Iron loses

Copper loses

Mechanical or electrical

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23
Q

Nema design A

The starting current in a stator is about ___ % of FLA

The starting torque in a rotor is about ____ % of full load torque.

The breakdown torque of a rotor is about ___ % of full load torque.

Study These Flashcards
A

600%

150%

200%

24
Q

Nema design B

The starting current in a stator is about ___ % of FLA

The starting torque in a rotor is about ____ % of full load torque.

The breakdown torque of a rotor is about ___ % of full load torque.

Study These Flashcards
A

500%

150%

200%

Most common

25
Nema design C The starting current in a stator is about ___ % of FLA The starting torque in a rotor is about ____ % of full load torque. The breakdown torque o Is produced at the instant of ____
500% 225% Start Has double squirrel cage
26
Nema design D The starting current in a stator is about ___ % of FLA The starting torque in a rotor is about ____ % of full load torque. The breakdown torque is produced at the instant of ____
400% 275% Start
27
Canadian electrical code allows ___% in rush
300%
28
Slip is ___% the instant a motor is energized
100%
29
A variable frequency drive (VFD) ....
Achieve speed control in wound rotor motors
30
Speed control of a wound rotor motor is most suitable from....
0 r/min to full load speed
31
Main disadvantage of a wound-rotor motor is....
Greater cost and higher maintenance
32
When a rotor is built with thinner rotor bars what happens?
Rotor resistance increases
33
List 3 advantages of a wound rotor induction motor
High start torque Low starting current Variable speed
34
List 4 disadvantages of a wound rotor induction motor
High cost Large frame More maintenance Low efficiency
35
Lap windings have coils with?
Varying pitch
36
A rotor spins in the same direction as the rotating magnetic field produced by the stator?
True
37
What are two major components of the stator?
Stationary iron Windings
38
Main purpose of the rotor is to produce?
Torque
39
The stator rotating magnetic field (RMF) rotates at a?
Constant speed
40
How many windings does a 4 pole three phase induction motor have?
12. (3x4)
41
Current listed on a motors nameplate is called?
Full load current
42
The speed listed on a motors nameplate is the?
Full load speed
43
What does an induction motor do?
It's a machine that gets energy into the rotating part by mutual induction
44
The transfer of energy from the stator to the rotor is achieved by?
Mutual induction
45
What is the function of the motor frame?
To protect the winding's and bearings
46
List 3 types of totally enclosed motors
Fan cooled Non ventilated Pipe ventilated
47
name 4 main parts of the stator
Laminated and slotted iron The conductors Conductors insulation Protective sleeves and wedges for the slots
48
What is the function of the stator core?
It provides a high permeability path for magnetism
49
What is the function of the stator winding?
To generate a rotating magnetic field which creates torque
50
Name 2 Types of rotors
Squirrel cage Wound rotor
51
The stator windings may be wound through the stator slot in two ways. What are they?
Lap windings Concentric windings
52
What's the function of the rotor?
Rotate and drive the motors output shaft to produce work
53
The squirrel cage rotor consists of aluminum or copper bars called?
Rotor conductors
54
Define rotor speed
It is the rotational speed of a rotor in an electric motor.
55
A wound rotor motor is?
The ideal induction motor. Combining the best starting characteristics. (High rotor resistance and low rotor inductance)
56
Wound rotor motors have several disadvantages such as
Higher cost Larger frame Extra maintenance

Motors (5 decks)

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