AC Generators Flashcards

0
Q

How does a current transformer sense the amount of current in a wire?

A

Through electromagnetic induction

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
1
Q

What are the required loads for a generator to supply to an aircraft?

A

Loads to a normally working system; essential loads after failed of and prime movers; essential loads after failure of any engine or multi-engine aircraft; essential loads for which AC source of power is required after any failure in one power supply system

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

How does an auto transformer work?

A

A tap contacts a single transformer coil at a point to output the exact required voltage.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What is the purpose of a bus bar?

A

A bus bar is used to distribute power over a set of contact points.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What are three circuit protection devices?

A

Circuit breakers, fuses, and current limiter

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What are the three types of circuit breakers?

A

Thermal, magnetic, thermal-magnetic

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What are the three types of fuses?

A

Normal, time delay, and very fast acting

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What are the 2 types of switches?

A

Toggle and rotary

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What are the requirements for aircraft wiring?

A

Design temperatures, flexibility, resistance, applied voltage, abrasion resistance, strength, insulation, weight, and current flow.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

How many strands are in a small and large wire?

A

7 or 19 for small.

19 or more for large.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What is the difference between relays and solenoids?

A

Solenoids have a moveable core. Solenoids have heavy contacts that are capable of handling high amounts of current.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What are the classifications of relays?

A

Control relays, power relays (line contractors), revers current relays

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What are Line contractors used for?

A

Controlling high voltages.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

What are special about AC line contractors?

A

They have three leads, one for each phase.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

How do reverse current relays work?

A

The generator powers a relay that, if not powered by the required voltage, opens, and prevents a current from flowing backwards to the generator.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What is a negative ground system?

A

The aircraft skin is a negative ground, providing a ground throughout the aircraft. This helps reduce the wires normally required for return grounds.

16
Q

What is shed and non-shed?

A

Non-Shed: essential for safe aircraft operation

Shed: convenience, non-essential

17
Q

What are some non-shed systems?

A

Essential lighting, flight control system, communication and nav radios, other high priority electrical systems.

18
Q

What type of Voltage is used in an aircraft?

A

115VAC, phase 3, 400 Hz

19
Q

How does a split bus system work?

A

Each bus can be powered by either generator, isolating the other in the event of failure, and automatically removes shed components

20
Q

What are the types of external sources for AC?

A

Essex mobile and Hobart power cart, hangar deck and flight line hard-wired AC power

21
Q

How many degrees is the sine wave of either phase from the other?

22
Q

What will a voltmeter read between 2 phases?

23
Q

What will a voltmeter read between a phase and neutral?

24
What is the name of the connection of the three phase leads?
Wye Connection
25
What are the components of a simple AC generator?
Pole pieces, armature loop, slip rings, and generator brush
26
What material are generator brushes made of?
High-grade carbon and graphite for the brush. | Copper for the pigtail
27
What is the name of the stationary and rotating components of a generator?
Stationary: Stator Rotating: Rotor
28
What are the benefits of a brushless generator?
Low maintenance cost, high stability and consistency, better performance t high altitude, require much less iron and weigh less.
29
Describe the PMG process.
The rotor shaft spins a permanent magnet generating a single phase AC current to go to the GCU. The GCU rectifies the voltage to DC and powers an exciter field for a 3 phase generator. The three phase gen goes through a rectifier creating a stable DC exciter. That spins with the shaft creating a rotating field generating 3 phase AC
30
What are the three factors that directly affect generator output?
The speed the armature rotates, number of conductors, the strength of magnetic field (what is controlled by the GCU)
31
What are the functions of GCU protection?
Voltage regulation, reverse current protection, under/over frequency, phase differences, feeder fault (shorts)
32
When is APU power generation used?
Before engine start, during ground maintenance, and in-flight emergency when primary AC fails
33
What are the outputs of a rotary inverter with an input of 28 VDC?
115 VAC, single phase, 400 Hz 115 VAC, three phase, 400 Hz 200 VAC, three phase, 400 Hz
34
What are the types of inverters?
Rotary (PMG and inductor) and Static
35
What is a major safety concern for operating external power?
Never disconnect the external power connector with the aircraft systems running or the external source on.
36
The External Power Monitor will disconnect external power from the aircraft if it senses any of the following:
Under Voltage, over Voltage, under-frequency, over-frequency, improper phase sequence