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Motors > A/B > Flashcards

A/B Flashcards

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.

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.

A

500%

150%

200%

Most common

25
Q

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 ____

A

500%

225%

Start

Has double squirrel cage

26
Q

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 ____

A

400%

275%

Start

27
Q

Canadian electrical code allows ___% in rush

A

300%

28
Q

Slip is ___% the instant a motor is energized

A

100%

29
Q

A variable frequency drive (VFD) ….

A

Achieve speed control in wound rotor motors

30
Q

Speed control of a wound rotor motor is most suitable from….

A

0 r/min to full load speed

31
Q

Main disadvantage of a wound-rotor motor is….

A

Greater cost and higher maintenance

32
Q

When a rotor is built with thinner rotor bars what happens?

A

Rotor resistance increases

33
Q

List 3 advantages of a wound rotor induction motor

A

High start torque

Low starting current

Variable speed

34
Q

List 4 disadvantages of a wound rotor induction motor

A

High cost

Large frame

More maintenance

Low efficiency

35
Q

Lap windings have coils with?

A

Varying pitch

36
Q

A rotor spins in the same direction as the rotating magnetic field produced by the stator?

A

True

37
Q

What are two major components of the stator?

A

Stationary iron
Windings

38
Q

Main purpose of the rotor is to produce?

A

Torque

39
Q

The stator rotating magnetic field (RMF) rotates at a?

A

Constant speed

40
Q

How many windings does a 4 pole three phase induction motor have?

A
  1. (3x4)
41
Q

Current listed on a motors nameplate is called?

A

Full load current

42
Q

The speed listed on a motors nameplate is the?

A

Full load speed

43
Q

What does an induction motor do?

A

It’s a machine that gets energy into the rotating part by mutual induction

44
Q

The transfer of energy from the stator to the rotor is achieved by?

A

Mutual induction

45
Q

What is the function of the motor frame?

A

To protect the winding’s and bearings

46
Q

List 3 types of totally enclosed motors

A

Fan cooled
Non ventilated
Pipe ventilated

47
Q

name 4 main parts of the stator

A

Laminated and slotted iron

The conductors

Conductors insulation

Protective sleeves and wedges for the slots

48
Q

What is the function of the stator core?

A

It provides a high permeability path for magnetism

49
Q

What is the function of the stator winding?

A

To generate a rotating magnetic field which creates torque

50
Q

Name 2 Types of rotors

A

Squirrel cage

Wound rotor

51
Q

The stator windings may be wound through the stator slot in two ways. What are they?

A

Lap windings

Concentric windings

52
Q

What’s the function of the rotor?

A

Rotate and drive the motors output shaft to produce work

53
Q

The squirrel cage rotor consists of aluminum or copper bars called?

A

Rotor conductors

54
Q

Define rotor speed

A

It is the rotational speed of a rotor in an electric motor.

55
Q

A wound rotor motor is?

A

The ideal induction motor. Combining the best starting characteristics. (High rotor resistance and low rotor inductance)

56
Q

Wound rotor motors have several disadvantages such as

A

Higher cost

Larger frame

Extra maintenance

Motors (5 decks)

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