Engine Electrical Systems Flashcards
(41 cards)
What is used as the rectifier to produce direct current in a DC generator?
Brushes and a commutator
If the installed ammeter gauge is redlined at 100% of generator or alternator rating, and the regulator does not control current, how is maximum current controlled?
current is controlled by the pilot by not applying loads greater than redline, except for short, intermittent loads
If placards or monitoring devices are not practical or desired, what practice protects the battery and electrical system?
The generator is sized so that total continuous load of the electrical system does not exceed 80% of the rated capacity of the generator or alternator
When determining maximum continuous electrical load of an aircraft, what defines if the load is intermittent or continuous?
The length of time the system is used. If the component or system is used for less than two minutes, it is considered an intermittent load. More than two minutes is considered continuous load.
How is generator output voltage controlled?
By controlling the field current strength through the use of a voltage regulator
How are wire sizes represented?
By a numbered gauge size. The smaller wires are represented by larger numbers. The smallest size wire normally used in an aircraft is 22-gauge.
What is the maximum slack allowed between the supports of a single wire or bundle installation?
Not over 0.5 inches.
Why are wires bonded on powerplant installations?
To provide a current return path for electrical accessories, and to prevent static discharge.
How is the voltage of a DC generator controlled?
By varying the field current strength.
What is the most common type of alternator used in most aircraft AC systems?
The three phase alternator.
How does a voltage regulator control the voltage of an alternator?
By regulating the voltage output of the DC exciter.
What does the speed of rotation and number of poles of an alternator determine?
The frequency of the alternator output.
What are some of the methods used to maintain 400 hertz alternator output frequency on large turbojet or turbofan engines? (3)
- Constant speed drives
- Integrated drive generators
- Variable- speed constant frequency power systems.
Name the major parts of a DC motor.
- The armature
- Field
- Brushes
- Frame assembly
Name the components of a direct cranking electric starter system.
- An electric motor
- Reducing gears
- An automatic engaging and disengaging mechanism
Name the three types of DC motors.
- Series
- Shunt
- Compound.
What type of DC motor is commonly used for a reciprocating engine starter and why?
A series wound motor is commonly used because it has a high starting torque under heavy loads conditions.
What are the operating modes of a turbine engine starter generator?
It operates first as a starter, then as a generator once the engine is running.
What is a possible indication when a starter drags?
A dirty or worn starter commutator.
Where would wire with high temperature insulation material be used?
When they run close to high temperature areas such as exhaust stacks or heating ducts.
What is the size standard for electrical wire used in US manufactured aircraft?
The American wire gauge (AWG).
What reduces arcing in the points and also aids the collapsing of the magnetic field in a magneto?
A magneto.
How does a magneto produce the high voltage required to fire a spark plug?
DELETE
In the rotation cycle, when the magneto rotor is in the E-gap position, the primary points open, which interrupts the current flow in the primary circuit causing a high rate of flux change in the core, and inducing a pulse of high voltage in the secondary coil.
What is the P-lead and how does it function?
The P-lead connects the ignition switch to the primary circuit of the magneto. When the ignition switch is turned off, the P-leads on both of the magnetos are grounded. When the ignition switch is turned to the “LEFT” position, the right magneto is grounded so that only the left magneto operates, and visa versa.
