Generators and Alternators
Alternators produce __________ phase AC in its _____________ windings.
3 and armature
Most AC electricity produced in an aircraft has what frequency?
400 Hz
What end of the generator is used to determine the direction of rotation for a given generator?
Indicated by an arrow marked on the cover plate of the brush housing to indicate rotation
Name two types of rectifiers.
Mechanical and electrical
Normally, what is the "coming in speed" for a typical generator?
Around 1500 RPM
What purpose do the brushes serve in a DC generator?
Brushes transfer electrical energy from the armature.
The AC frequency induced into the alternator stator is determined by what factors?
By the number of poles and the speed of the rotor, or engine Rpm.
How can residual magnetism be restored within the field shoes?
By turning the field coil
How many revolutions of the armature is required to produce 400 cycles of AC electricity?
One rotation of the armature produces one cycle of AC, so 400 rotations would equal 400 cycles.
What are the three different classifications of DC generators?
Series wound, shunt wound, compound wound.
What type of voltage regulator does a alternator use?
Soild-state regulators known as ACU's controls voltage regulation.
What is the primary purpose of an aircraft storage battery?
The primary purpose for an aircraft storage battery is to start the engines and provide an emergency power source
Describe the field coils within a Series-Wound DC generator.
Coils, armature, and load are connected in series are composed of a few turns of large wire because the must carry the full load current.
What device within a DC generator changes the AC it produces into DC?
Commutator
What are the three basic parts of the armature?
Commutator, windings, driveshaft
Varying the alternator __________________________________, controls its voltage output?
DC Exciter
Increasing the number of coils/windings in the armature has what effect on the output of a generator?
Generator output would increase due to the magnetic field being stronger.
What three factors affect a generators voltage output?
# of poles, RPM, # of loads
What is the only practical means for controlling the output of a generator?
A field rheostat
Alternators are classified according to what 3 characteristics?
By type of excitation, number of phases, and type of rotor and stator.
All generators and alternators produce what type of electricity?
AC and DC
What four parts make up an aircraft electrical production system?
Generation, regulation, distribution, and protection.
A ________ produces electricity by rotating a conductor thru a stationary magnetic field.
Generator
How are alternators rated?
They are by voltage and amps.
What type of rectifier does an alternator use?
A full wave rectifiers.
Name three sources of electrical power on an aircraft.
Aircraft battery( chemical), external power, Alt/Gen(magnetism)
A ________ produces electricity by rotating a magnetic field across a stationary conductor.
Alternator
Which classification of DC generators is normally used for light to medium use on an aircraft?
Compound wound
A vibrating voltage regulator controls the output of a DC generator by reducing _____ to the generators field coil?
Current
Name the parts of a generators voltage regulator.
Current regulator, voltage regulator, and cutout relay.
Describe the field coils within a Shunt-Wound DC generator.
Current that flows through the load, also flows through the field coils in parallel
Describe the field coils within a Shunt-Wound DC generator
Current that flows through the load, also flows through the field coils in parallelcontains many turns of small wires
How many diodes are found in a DC alternator?
Dc alternators have 6 diodes.
Compressing the carbon piles in a carbon-pile voltage regulator has what affect on the output of a DC generator?
Decreases generator output
Name the two types of alternator rotor windings.
Delta-wound stators, and Y-wound stators.
Name four excitation methods for exciting the alternator rotor assembly.
Directly connected, Transformer/Rectifier, brush, and integrated brushless.
What is the purpose of a reverse-current relay?
Disconnects the battery from the generator when the generator output is lower than the battery output
What turns the armature in generator?
Drive shaft or pulleys turns the armature
What type of rectifier does a generator use?
Electrical
What are the four basic parts of a generator?
Field shoes, field coil, armature, brushes, driveshaft
What two things does filtering the output of rectifier provide?
Filtering provides a smoother signal.
How are the field coils/windings normally energized within a DC generator?
From an external source or from the current generated by the unit itself
Where does the alternator rotor get its excitement voltage?
From the aircraft battery.
Define the term "Voltage Regulation".
It is control over the field current, which in turn controls generator output.
In accordance with 14 CFR part 23 state four requirements of an aircraft electrical system.
It must work independently, each generator must be able to supply continuous rated power, must have over voltage control devices, and should have an ammeter.
The output of an alternator is taken directly from what part of the alternator?
It taken directly from the rectifiers and fed directly to the bus.
What can cause a loss of residual magnetism within a generators field shoes?
Lack of use, load being connected when not running, no load for extended periods of time, eddy current
What is the purpose of the current limiter circuit in a voltage regulator?
Limits the output current of the generator
What are the three requirements for electromagnetic induction?
Magnetic Field, Conductor, Motion
Name the 3 different types of aircraft electrical busses.
Main AC, Main DC, Avionics, Emergency, and Auxiliary.
How are generators rated?
The Voltage (E) and Current output (A)
The AC frequency produced by an AC Alternator is determined by what by what?
The frequency is determined by the number of poles and the speed of the rotor, or engine rpm.
What is meant by generator "coming in speed"?
The generator speed at which they begin to produce their normal voltage (around 1500 RPM)
According to the "left hand rule for generators", the thumb indicates what?
The middle indicates direction of current, the pointer finger, magnetic field off of pointer finger, direction of force for thumb.
What alternator part produces the electromagnetic field?
The rotor which has the coil windings
How many rectifiers does an alternator have?
Three full wave rectifiers.
Alternators are classified by what three characteristics?
Type of excitation, number of phases, and type of rotor and stator.
DC alternators change __________________________energy into electrical energy by the process of __________________ ______________________.
electromagnetic, rectification
The output of an alternator is determined by varying the _____________________ voltage.
input
What are the advantages of an alternator over a generator?
lighter and more efficient.
An alternator rotor produces the ________________ field.
magnetic
How many rectifiers does a typical alternator use?
three full wave rectifiers are used.
What device controls the output of a generator?
-GCU (Generator Control Unit)
The generator is geared to spin the generator at ___ and ___ times the engine crankshaft speed.
1 1/8 and 1 1/2
Alternators use what type of rectifiers?
Solid-state rectifiers which are full wave rectifiers.
