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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
Output voltage generated by an alternator is ac or dc
AC
26
High speed rotors are called?
Cylindercal (High speed cindy)
27
Rotor with projecting poles is a?
Salient pole rotor Saleint proj pole
28
Eddy current losses are with
Iron or core loss
29
Voltage generated in the armature of the rotating field alternator depends on what 3 things?
# of armature turns per winding Speed of the rotating field Amount of flux produced by the rotating feild
30
Change the value of voltage that is generated is by?
Altering the field flux
31
Feild flux depends on 3 things?
# turns in feild winding Type of core material Amount of current flowing thru field windings
32
Alternator is not loaded what happens with Egen and terminal voltage?
They equal each other
33
4 conditions that need to be met a incoming alternator is in syncronism with the running alternator?
Phase sequence Terminal voltage Frequency Voltage phase position
34
Phase sequence is also called?
Phase rotation
35
What is phase sequence?
Incoming alternator must match phase sequence of the running alternator or supply system
36
Most common way to check phase sequence?
3 dark lamp method
37
When there is no potential difference in the 2 phase voltages what happens to the lamps
All 3 lamps are dark
38
3 lamps must be suitable for _______ the alternator phase voltage value?
Twice
39
Phase voltage When the 2 voltages of the alternator are 180° out of phase the voltage across the lamps is?
Double of the generated voltage of one alternator
40
Terminal voltage Incoming generator is usually ____ higher/lower than the running generator?
1-2 volts Higher
41
Frequency Can a 6 pole 1200r/min and 2 pole 3600r/min be added to a 4 pole 1800r/min?
As long as the frequency is the same
42
Adding a alternator does the frequency have to be the same?
Yes but the incoming generator is 1-2 hertz higher than the running gen
43
Synchronscope does what?
Indicates frequency and phase position and is commonly used to determine phase relationship
44
On a synchronscope if the pointer moves clockwise the incoming alternator is ______ than the running alternator?
Higher
45
On a synchronscope if the pointer is moving counter clockwise than the incoming frequency is ?
Lower Counter=lower
46
When the pointer on s synchronscope is stopped pointing up what does that mean?
Both frequencies are equal
47
Easier for a incoming alternator to (slow down or speed up) to a running alternator?
Easier for it to slow down
48
At full load the current on the armature/sator will be _______ than the current on the field windings?
Higher
49
Current flowing in the stator is ac or dc
AC
50
Current flowing incthe rotating field is ac or dc
DC DC Rots
51
Reversing the direction of the prime mover will change phase sequence TorF
True
52
If the line, phase and winding current is the same the alternator is wye or delta?
Wye
53
Alternator efficency compares input and output of what?
Watts
54
Field windings are ac or dc
DC
55
The armature voltage on a Alternator is AC?
AC
56
Slip rings are used to connect VDC to the rotating cct via brushes? TorF
True
57
A alternator is salient type or cylindrical
Salient
58
Bearing friction and windage is examples of?
Mechanical losses
59
Do basic alternators have commutators and armatures?
No
60
Maximum efficiency of a alternator it must operate at?
Rated load and unity pf
61
Voltage induced in a ac generator depends only upon ______ and the ____
Field current Speed of the rotor
62
2 alternators operate in parallel should do what with the load?
Each should supply 50%
63
Negative pf would lead or lag
Lead
64
Postive would lead or lag?
Lag
65
Oscillation is called?
Hunting

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