Alternator Types PDF: Learn About Different Types of Alternators

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Questions and Answers

What is the main advantage of using a permanent magnetic generator (PMG) over a brushed generator?

PMGs can operate in both voltage and current modes.

PMGs require less maintenance due to the lack of brushes and slip rings. (correct)

PMGs are more efficient at high altitudes.

PMGs can provide power to ignition exciters and FADECs.

Why are brushless alternators more efficient at high altitudes compared to brushed alternators?

Brushless alternators have a more robust design that is better suited for high altitude conditions.

Brushless alternators have a more efficient cooling system.

Brushless alternators have a higher power output.

Brushless alternators do not experience brush arcing, which is a common problem at high altitudes. (correct)

What is the purpose of the exciter field in a brushless alternator?

To control the output voltage of the generator.

To regulate the current flow to the main output field.

To provide the initial magnetic flux to start the generator.

To induce voltage into the main output field. (correct)

What is the role of the permanent magnets in a brushless alternator?

They provide the initial magnetic flux to start the generator. Signup and view all the answers

Which of the following is NOT a key component of a brushless alternator?

Brushes and slip rings Signup and view all the answers

What is the primary purpose of a brushless alternator in a gas turbine engine?

To provide power to the ignition exciter. Signup and view all the answers

What is the key difference between a revolving armature type alternator and a revolving field type alternator?

The rotor is the field in the revolving armature type, while the rotor is the armature in the revolving field type. Signup and view all the answers

Why is the rotating armature configuration generally not used to supply electric power in large quantities?

The rotating armature configuration requires slip rings and brushes to connect the armature output voltage and current to the load. Signup and view all the answers

What is the key similarity between a DC generator and a revolving-armature alternator?

Both have a rotating armature and a stationary magnetic field. Signup and view all the answers

What is the main advantage of the revolving field type alternator over the revolving armature type?

The revolving field type does not require slip rings and brushes. Signup and view all the answers

Which type of alternator is generally used to supply electric power in large quantities?

Revolving field type Signup and view all the answers

What is the purpose of the slip rings in a revolving-armature alternator?

To connect the armature output voltage and current to the load. Signup and view all the answers

What happens when the rotor poles are opposite the windings of Phase B in the alternator?

Maximum voltage is induced in Phase B Signup and view all the answers

How much rotor rotation corresponds to one quarter of a cycle in the alternator?

90° Signup and view all the answers

What is the relationship between the voltages induced in Phase A and Phase B in the two-phase alternator?

They are 90° out of phase Signup and view all the answers

What is the purpose of the B1-A2 connection made internally in the two-phase three-wire alternator?

To provide a new output voltage Signup and view all the answers

What effect does connecting one end of B1 to one end of A2 have on the alternator's output?

Results in a new output voltage, C, larger than A or B Signup and view all the answers

What is unique about the output connections in a two-phase, three-wire alternator compared to a standard alternator?

Only three connections are brought out from the stator Signup and view all the answers

When the waveform is below the time axis, what is said to be flowing in a negative direction?

Current Signup and view all the answers

What is the total number of degrees in a complete cycle?

360 Signup and view all the answers

At the initial position of 0, what is happening to the armature conductors?

They are moving parallel to the magnetic field Signup and view all the answers

As the armature rotates from 90 to 180, what happens to the induced voltage?

It decreases from a maximum positive value to zero Signup and view all the answers

What is the direction of the induced voltage as the armature rotates from 180 to 270?

Negative Signup and view all the answers

What type of alternator produces a single, continuously alternating voltage?

Single-phase alternator Signup and view all the answers

What is the relationship between the line voltage and phase voltage in a wye-connected three-phase system?

The line voltage is 1.73 times the phase voltage. Signup and view all the answers

What is the relationship between the line current and phase current in a wye-connected three-phase system?

The line current is equal to the phase current. Signup and view all the answers

How is the neutral connection used in a wye-connected three-phase system?

The neutral connection is used to supply single-phase voltage. Signup and view all the answers

What is the significance of the 'wye' connection in a three-phase system?

The windings appear as the letter 'Y' without the neutral connection. Signup and view all the answers

What is the purpose of the $ ext{sqrt}{3}$ factor in the relationship between line and phase voltages in a wye-connected three-phase system?

To convert from phase to line voltage. Signup and view all the answers

What is the main advantage of a wye-connected three-phase system over a delta-connected system?

Ability to supply single-phase loads. Signup and view all the answers

Study Notes

Permanent Magnetic Generators (PMGs)

No requirement for power supply to the field, eliminating the need for brushes or slip rings
Can be designed to operate in voltage mode (open circuit) or current mode (closed circuit)
Crucial components for providing power to ignition exciter, FADECs, or other accessories on gas turbine engines

Brushless Alternators

Used in large jet-powered aircraft
No current flow between brushes or slip rings, making them efficient at high altitudes
Consist of three separate fields: permanent magnetic field, exciter field, and main output field
Permanent magnets induce voltage into the armature, carrying current to a generator control unit (GCU)