Alternators Flashcards

1
Q

Name the two other names for Alternators.

A

Synchronous Generators
Alternating current generators

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2
Q

Describe a rotating field alternator.

A

Has rotating field windings
Excitation current is supplied through brushes and slip rings from an external dc source
Armature directly connected to an external load

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3
Q

The two distinct types of synchronous-generator rotating field structures are?

A

Cylindrical - smooth exterior, long, well balanced
Salient (projecting) - shorter in length, wide

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4
Q

What sort of conversion of energy happens in the armature winding?

A

Mechanical to Electrical

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5
Q

A one-turn stator winding in an alternator generates one-quarter the voltage of a comparable four-turn winding. T or F?

A

True
E•G
One Turn Coil= 30V
Four Turn Coil= 120V

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6
Q

In regards to a parallel delta-connected, three-phase, twelve-lead alternator, how would you find the current in a winding?

A

Divide Iphase by two to get the current per winding

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7
Q

How do you reduced Hysteresis Losses?

A

Alloys such as silicon steel or iron with silicon in it are used in the core material.

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8
Q

Heat losses produced by current in windings of the alternator are called?

A

Copper Losses

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9
Q

The power required to drive the built-in cooling fan of an alternating current generator is known as what type of losses?

A

Mechanical Losses

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10
Q

In an alternator, the slip rings are stationary. T or F?

A

False. Slip rings are attached to the rotor.

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11
Q

The Output Voltage of an Alternator is due to three factors:

A

Armature: Resistance, Reactance & Reaction

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12
Q

A solid state rectifier is an example of a external dc supply. T or F?

A

True

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13
Q

In a brush-type, self-excited alternator, a small shunt is mounted on the same alternator shaft that supports the main alternator rotor and field windings. T or F?

A

True

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14
Q

A brushless excitation system does not require a commutator. T or F?

A

True

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15
Q

Four conditions must be met before syncing two parallel alternators. State them:

A

Phase Sequence
Terminal Voltages
Frequencies
Phase Position

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16
Q

Using the “three-dark lamp method” the lamps must be suitable for what rating?

A

Twice the alternators phase voltage value

17
Q

A synchroscope indicates what values?

A

Frequency and Phase Position of the incoming alternator relative to the running alternator or supply voltage

18
Q

If a synchroscope pointer moves CCW, what does that indicate?

A

The frequency of the incoming alternator is lower than that of the running alternator.

19
Q

The 12 o’clock position of a synchroscope means the frequency and phase position have all matched up. T or F?

A

True

20
Q

How do you transfer the power load of ALT 1 to ALT 2 without changing frequency?

A

Increase the power input or the torque of the prime mover of ALT2 and simultaneously decrease the power input to ALT1

21
Q

To increase the output voltage of a system supplied by two paralled alternators, the field excitation of both alternators needs to be increased. T or F?

A

True

22
Q

A heavy flywheel reduces hunting. What other application reduces hunting?

A

Embedded amortisseur (dampen) windings in the surface of the alternator’s rotor pole faces produce an induced current that opposes and limits the action of hunting.