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Electrical Theory L2 > Test 1 Magnetism, Motors, Generators > Flashcards

Test 1 Magnetism, Motors, Generators Flashcards

1
Q

How do you de-magnetize magnetic material

A

Hitting it with a hammer, and/or heat

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2
Q

Magnetic inductors oppose a change in?

A

Current

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3
Q

1 Horsepower (HP) is equal to how many Watts?

A

746W

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4
Q

What DC motor has the best Torque Characteristics

A

Series motor

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5
Q

What is the name of a natural Magnet

A

Magnetite/lodestone

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6
Q

What type of voltage is in a rotating generator

A

AC voltage

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7
Q

Other DC motor types?

A

Permanent Magnet
DC servo
Brushless

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8
Q

What is the opposing force in a motor?

A

CEMF (counter electromotive force)

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9
Q

What shape are field windings?

A

Square

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10
Q

Unlike poles do what?

A

Attract

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11
Q

Like poles do what?

A

Repel

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12
Q

Electromagnetism occurs when current passes through?

A

The Conductor

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13
Q

What does the Commutator do?

A

Changes AC to DC
And
Maintains the proper polarity of the dc voltage

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14
Q

Brushes ride against what component?

A

The Commutator

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15
Q

How can you compensate for armature reaction

A

• Compensating Windings
• Adjust brushes to compensate for new point of neutral plane
• Interpoles

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16
Q

Another term for armature?

A

Rotor

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17
Q

The amount of voltage induced in in a conductor is affected by

A

• Turns of wire
• Strength of magnetic field
• Speed of cutting action

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18
Q

The time constant for voltage to be fully induced?

A

5 times

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19
Q

How to change the direction of the armature

A

Reverse the connections (change the Armature leads)

20
Q

In the right hand rule, what does the middle finger indicate?

A

Direction of Current

21
Q

What current causes excessive heat in the metals core material

A

Eddy current

22
Q

Lenz’s law states what?

A

The direction ofInduced current will oppose the motion that caused it

23
Q

Interpoles can be found in between?

A

Between the main poles

24
Q

How is the shunt field connected to the armature

A

In parallel

25
Q

2 methods to prevent voltage spikes

A

Diodes and Resistors

26
Q

What is permeability?

A

The ability to conduct magnetism

27
Q

Large spikes of voltage can be used for what?

A

Cow Fences

28
Q

Induction occurs when what passes through the magnetic field?

A

Conductor

29
Q

Separately excited shunt field is a shunt field that has

A

A different power supply

30
Q

Motors use what to rotate the armature?

A

Attraction and repulsion

31
Q

How do you control field excitation in a series shunt field motor?

A

Rheostat (variable resistor)

32
Q

Losses in a motor are?

A

• Windage Losses
• I^2 R
• Bearing Friction

33
Q

3 factors that affect output voltage of a DC generator

A

Conductor loops in the armature
Armature speed
Magnetic field strength

34
Q

Easily magnetized materials are known as?

A

Ferromagnetic

35
Q

What is it called when magnetism is still left in a motor that has been shut off?

A

Residual magnetism

36
Q

Difference between generator and motor?

A

Generator: Converts mechanical energy into electrical
Motor: Converts electrical energy into mechanical

37
Q

What is coercive force?

A

A materials ability to stay magnetized after the magnetic force is removed

38
Q

What is flux density?

A

The magnetic field strength of the lines of force

39
Q

What is the north poles true polarity?

A

South polarity

40
Q

How can you produce AC voltage?

A

Slip rings

41
Q

Unit of measurement for an inductor?

A

Henry

42
Q

Compound Generator is made up of _______ Shunt and ______ Shunt.

A

Long and Short

43
Q

Left hand rule, what does the middle finger signify

A

Current

44
Q

What is it called when there is 0 Volts in the commutator?

A

Neutral Plane

45
Q

When the North Pole and South Pole don’t line up with the true magnetic poles

A

Declination

46
Q

How is a series motor connected?

A

In Series

Electrical Theory L2 (3 decks)

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