Explanations: Aircraft Electrical Systems Flashcards

1
Q

Why is a ring type electrical terminal used on most aircrafts?

A

If the nut on the terminal stud becomes loose, the ring-type terminal will remain on the stud whereas a hook or slotted terminal will slip off.

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

What happens when the load of a generator equipped with a vibrator-type voltage regulator is great?

A

The voltage drops and the voltage regulator points must remain closed longer to allow the voltage to rise.

When the load is light, the voltage is high and the points remain closed a very short time.

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

What is generator brush arcing?

A

an excess spark, which can be caused by the brushes not having proper contact with the commutator.

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

Why does a series wound motor have high starting torque?

A

the same current that passes through the armature also passes through the field windings.

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

What happens if the frequency of two ac generators connected in parallel are not equal?

A

A mismatch in frequencies of the two AC generators will cause the generator with the lower frequency to be picked up as a load on the other generator (a condition referred to as “motoring”). This can cause an overload in the generators and the distribution system.

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

What does a armature brake do?

A

It causes the armature to stop turning as soon as the switch is released.

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

What will happen if armature reaction is not corrected?

A

It will cause the brushes to arc under certain load conditions.

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

What is armature reaction?

A

Armature reaction weakens the main flux. In the case of a dc generator, the weakening of the main flux reduces the generated voltage

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

What are interpoles?

A

Interpoles are small electromagnets placed between the main poles of a generator. They are used to improve the performance of the generator by reducing voltage fluctuations and increasing the efficiency of the machine.

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

What are pole pieces (or poles shoes)?

A

A structure composed of material of high magnetic permeability that serves to direct the magnetic field produced by a magnet. A pole piece attaches to and in a sense extends a pole of the magnet, hence the name. Pole pieces are used with both permanent magnets and electromagnets.

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

What are field coils?

A

A coil that generates a magnetic field when an electric current is passed through it.

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

What are current cutout relays?

A

Sometimes called the circuit breaker, this device is a magnetic “make-and-break “ switch. It connects the generator to the battery circuit when the generator’s voltage builds up to the desired value. It disconnects the generator when it slows down or stops.

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

How does the magnetic brake used to stop rotation of an electric motor armature operate?

A

a magnetic brake used to stop rotation of an electric-motor armature is applied by spring force and is released by an electromagnet energized when the motor is turned on.

As soon as the motor is turned off, the spring applies the brake and stops the rotation of the armature.

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

What is a brush pigtail?

A

A pigtail connects a brush to the power supply. A pigtail is an extended, flexible connection or a braided copper conductor. Brush material must have good conductivity and be soft enough not to damage the copper segments of the commutator.

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

How does the brush pigtail eliminate sparking?

A

All of the current is carried from the brush into the holder through the pigtail rather than through the sliding contact made between the brush and the brush guide.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

Why does a series-wound DC electric motor require less current at high RPMs?

A

The current drops off as the armature speed and the counter EMF builds up.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

What are the purposes of interpoles?

A

They are used in high-output compound-wound DC generators to counteract field distortion and to overcome armature reaction. Armature reaction causes arcing at the brushes.

They don’t reduce field strength, they increase it.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

When a DC generator is overhauled, what is done with the commutator?

A

It is turned on a lathe until it is perfectly round and smooth.

After the commutator it turned, the mica separators between the commutator bars are undercut to approximately the width of the mica, or somewhere in the neighborhood of 0.02 inch.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

Where is the integral fan of a generator mounted?

A

on the armature shaft.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

How does a rectifier work?

A

It allows electrons to flow in one direction, while blocking the flow of electrons in the other direction.

21
Q

How do you know if a diode is functioning properly?

A

After being disconnect from the circuit, it’s resistance should be checked with an ohmmeter.

It is good if it has high resistance in one direction but low resistance in the other.

The diode is shorted if both readings are low, and it is open if both are high.

22
Q

Why must a capacitor be fully discharged before removing it from a circuit?

A

because i’ts dangerous yo. shock you yo.

23
Q

When does thermal runaway occur in a nickel-cadmium battery?

A

when some of the cells become excessively hot.

The heat lowers both the voltage and the resistance so the cells can accept a high rate of charging current. This high current produces more heat and the battery can destroy itself.

24
Q

Explain series, shunt, and compound motors.

A

series are in series, shunt are in parallel, compound are a combination of the two.

25
Q

Why are soldered terminals not considered satisfactory for aircraft wiring?

A

the vibration will likely cause them to break off of the wire.

Crimped terminals transmit the tension and vibration loads into the terminal and do not cause stress concentrations.

26
Q

Why is the pin section of an AN/MS connector installed on the ground side and the socket on the “hot” side?

A

This arrangement minimizes the possibility of a short between a connector and ground when the connectors are separated.

27
Q

What is a DC exciter?

A

Exciter or DC generator relay is a device which forces the DC machine-held excitation to build up during starting or which functions when the machine voltage has built up to a given value.

28
Q

What causes radio frequency potentials?

A

A buildup of static charges, which are normally dissipated by grounding. Static charges cause sparks to jump and these sparks produce radio frequency energy.

29
Q

What may rapidly corrode a bonding connection?

A

electrolytic action. Copper jumpbeers may be safely used to bond together noncontinuous stainless steel components.

30
Q

What is a rheostat?

A

A variable resistor which is used to control current. They are able to vary the resistance in a circuit without interruption. The construction is very similar to the construction of potentiometers. It uses only two connections, even when 3 terminals (as in a potentiometer) are present.

31
Q

What is oil canning?

A

When you put oil in a can.

32
Q

What is oil canning, really?

A

the condition of a piece of sheet metal that causes it to snap back and forth when it is distorted or vibrated. If the sides of an electrical junction box oil-can, there is a possibility of some of the wires becoming shorted.

33
Q

How are terminal studs anchored against rotation?

A

by using a square end on the stud set into a square hole in the terminal strip.

34
Q

What is the voltage drop method of checking circuit resistance?

A
35
Q

The output of a DC generator normally has some AC noise caused by brush arcing superimposed on it. This AC can cause radio interference, and it may be removed by connecting a capacitor between the armature and ground, in parallel with the armature windings. The AC passes to ground through the low impedance path provided by the capacitor.

A

I know that already.

36
Q

What is the general rule of thumb for replacing aluminum electrical cable with copper?

A

the copper should be two wire gages smaller.

37
Q

AC 43.13-1 paragraph 426(c) please

A

in installations where the ammeter is in the generator or alternator lead and the regulator system does not limit the max current the generator or alternator can deliver, the ammeter can be redlined at 100 percent of the generator or alternator rating.

38
Q

What is the maximum permissible resistance value of a bonding connection?

A

0.003 ohm.

39
Q

why is it important to use derated switches for known continuous load current applications?

A

These loads either have abnormally high current inflow when the switch is first closed, or else they have extremely high voltage from an induced load when the switch is opened.

40
Q

14 CFR Part 23 states what? Repeat to me the entire thing.

A

each resettable circuit protective device must be so designed that a manual operation is required to restore service after tripping.

41
Q

How do you change the voltage of a transformer?

A

by passing an alternating current through it.

42
Q

What are eddy currents?

A

Eddy currents are loops of electrical current induced within conductors by a changing magnetic field in the conductor according to Faraday’s law of induction. Eddy currents flow in closed loops within conductors, in planes perpendicular to the magnetic field.

43
Q

How does a generator operate after the positive field lead is broken?

A

With both ends of the field at ground potential there can be no field current. The only magnetic field for armature windings to cut is that caused by the permanent magnetism in the generator field frame.

Permanent magnetism in the field frame produces residual voltage, which is somewhere between one and two volts.

44
Q

How do you flash a field?

A

You approach a field and quickly open wide your trench coat.

Then you momentarily pass direct current from the battery through the generator field coils in the normal direction of current flow.

45
Q

What type of rotor does an inductor-type inverter use?

A

it uses a rotor made of soft iron laminations. Grooves are cut laterally across the surface of the rotor to provide poles that correspond to the stator poles.

The voltage produced by an inductor-type inverter is controlled by the DC stator-field current.

46
Q

How does a voltage regulator vary the resistance of the generator field circuit?

A

By using a carbon-pile voltage regulator, a vibrator-type voltage regulator, or a transistor voltage regulator.

The resistance in the field circuit determines the amount of field current allowed to flow.

47
Q

What does an inverter do?

A

It converts dc to ac, much to ACDC’s chagrin.

48
Q
A