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Machines > Alternators Mod D > Flashcards

Alternators Mod D Flashcards

1
Q

What does a alternator convert?

A

Mechanical to electrical energy

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2
Q

In an alternator, what creates electrical energy?

A

Relative motion

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3
Q

What is relative motion?

A

A conductor moving thru a magnetic feild. Vise vera

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4
Q

Other names for a alternator?
2 names

A

Synchronous generator
Alternating current generator

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5
Q

4 advantages of a rotating field alternator?

A

Slip and brush not needed for armature output to load

Low current

Feild is physically smaller

Easy to cool down

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6
Q

2 types of rotor design?

A

Cylindrical rotor
Sailient pole rotor

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7
Q

Frequently (hz) formula

A

Poles X rpm /
120

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8
Q

Voltage generated by each winding is proportional to what?

A

Nunber of turns in the winding

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9
Q

Cylindrical rotors have how many magnetic poles

A

2 - 4

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10
Q

Alternators with Salient pole rotors have faster or slower prime movers?

A

Slower
Sail slow

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11
Q

Single phase armature windings can be connected in series or parallel?

A

Parallel and series

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12
Q

Voltage generated by each winding in the stator is _________ to the number of turns of the winding?

A

Proportional

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13
Q

3phase stator windings are places ____ mechanical degrees apart

A

120°

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14
Q

3phase stator winding wye or delta?

A

Either

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15
Q

4 Alternator losses?

A

Mechanical
Iron
Copper
Separately-excited feild cct losses

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16
Q

Iron losses also called?

A

Core losses

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17
Q

Two major losses in irons losses

A

Eddy current losses
Hysteresis losses

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18
Q

The cores ability to hold magnetism is called?

A

Retentivity

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19
Q

Copper losses is?

A

Heat losses produced by current in the windings

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20
Q

What do they use on large alternators to cool them down?

A

Coolants like hydrogen gas or water
Pg13

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21
Q

Alternator brushes are stationary or not?

A

Stationary

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22
Q

Alternator slip rings stationary?

A

Nope

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23
Q

Excitation current that creates the magnetic field in a alternator is ac or dc

A

Dc source

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24
Q

2 things you need to establish relative motion between the armature and the feild in a alternator

A

Rotor and stator

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25
Q

Output voltage generated by an alternator is ac or dc

A

AC

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26
Q

High speed rotors are called?

A

Cylindercal
(High speed cindy)

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27
Q

Rotor with projecting poles is a?

A

Salient pole rotor
Saleint proj pole

28
Q

Eddy current losses are with

A

Iron or core loss

29
Q

Voltage generated in the armature of the rotating field alternator depends on what 3 things?

A

of armature turns per winding

Speed of the rotating field

Amount of flux produced by the
rotating feild

30
Q

Change the value of voltage that is generated is by?

A

Altering the field flux

31
Q

Feild flux depends on 3 things?

A

turns in feild winding

Type of core material

Amount of current flowing thru field windings

32
Q

Alternator is not loaded what happens with Egen and terminal voltage?

A

They equal each other

33
Q

4 conditions that need to be met a incoming alternator is in syncronism with the running alternator?

A

Phase sequence
Terminal voltage
Frequency
Voltage phase position

34
Q

Phase sequence is also called?

A

Phase rotation

35
Q

What is phase sequence?

A

Incoming alternator must match phase sequence of the running alternator or supply system

36
Q

Most common way to check phase sequence?

A

3 dark lamp method

37
Q

When there is no potential difference in the 2 phase voltages what happens to the lamps

A

All 3 lamps are dark

38
Q

3 lamps must be suitable for _______ the alternator phase voltage value?

A

Twice

39
Q

Phase voltage
When the 2 voltages of the alternator are 180° out of phase the voltage across the lamps is?

A

Double of the generated voltage of one alternator

40
Q

Terminal voltage
Incoming generator is usually ____ higher/lower than the running generator?

A

1-2 volts Higher

41
Q

Frequency
Can a
6 pole 1200r/min and
2 pole 3600r/min be added to a
4 pole 1800r/min?

A

As long as the frequency is the same

42
Q

Adding a alternator does the frequency have to be the same?

A

Yes but the incoming generator is 1-2 hertz higher than the running gen

43
Q

Synchronscope does what?

A

Indicates frequency and phase position and is commonly used to determine phase relationship

44
Q

On a synchronscope if the pointer moves clockwise the incoming alternator is ______ than the running alternator?

A

Higher

45
Q

On a synchronscope if the pointer is moving counter clockwise than the incoming frequency is ?

A

Lower
Counter=lower

46
Q

When the pointer on s synchronscope is stopped pointing up what does that mean?

A

Both frequencies are equal

47
Q

Easier for a incoming alternator to (slow down or speed up) to a running alternator?

A

Easier for it to slow down

48
Q

At full load the current on the armature/sator will be _______ than the current on the field windings?

A

Higher

49
Q

Current flowing in the stator is ac or dc

A

AC

50
Q

Current flowing incthe rotating field is ac or dc

A

DC
DC Rots

51
Q

Reversing the direction of the prime mover will change phase sequence TorF

A

True

52
Q

If the line, phase and winding current is the same the alternator is wye or delta?

A

Wye

53
Q

Alternator efficency compares input and output of what?

A

Watts

54
Q

Field windings are ac or dc

A

DC

55
Q

The armature voltage on a Alternator is AC?

A

AC

56
Q

Slip rings are used to connect VDC to the rotating cct via brushes? TorF

A

True

57
Q

A alternator is salient type or cylindrical

A

Salient

58
Q

Bearing friction and windage is examples of?

A

Mechanical losses

59
Q

Do basic alternators have commutators and armatures?

A

No

60
Q

Maximum efficiency of a alternator it must operate at?

A

Rated load and unity pf

61
Q

Voltage induced in a ac generator depends only upon ______ and the ____

A

Field current
Speed of the rotor

62
Q

2 alternators operate in parallel should do what with the load?

A

Each should supply 50%

63
Q

Negative pf would lead or lag

A

Lead

64
Q

Postive would lead or lag?

A

Lag

65
Q

Oscillation is called?

A

Hunting

Machines (2 decks)

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