Airframe Electrical midterm Flashcards
(80 cards)
Give the three purposes of the primary battery in an aircraft application.
Ground ops (engine startup)
To absorb spikes from the generator/alternator
Emergency backup voltage
Name the two minimum controls necessary for any alternator.
Voltage regulator and current limiter.
What are the two batteries most widely used in aircraft application? Are they primary or secondary cells?
NiCads, lead acid, secondary cells.
State lenz’s law.
An induced emf always gives rise to a current whose magnetic field opposes the original change in magnetic flux.
What battery terminal must be disconnected first and reconnected last?
The negative terminal.
Name and explain the basis of the principles of operation of both generators and alternators.
Electromagnetic induction: electrical energy is produced by cutting lines of flux.
Name the four major components of a generator.
Field, armature, brush assembly, structural parts.
What principle is the operation of a generator based on?
Electromagnetic induction.
What does initial excitation in a generator come from?
It is provided by lines of flux produced by what is called “residual magnetism”
What are the three types of windings of a generator?
Shunt, series, compound.
What is excitation current?
The current passed through the electromagnet, used to produce, strengthen and control the flux field.
What is the purpose of the field in a DC generator?
To provide lines of magnetic flux for the conductor to cut through.
Describe the construction of a field in a DC generator.
Soft iron highly permeable cores called pole shoes are wrapped with copper wire (field windings), the pole shoes hold the windings in place.
What is the purpose of the armature in a generator?
It acts as a conductor, which cuts the lines of flux, into which the voltage is induced to produce current.
Describe the construction of the armature in a generator.
It consists of windings of wire called armature coil, multiple windings are used to increase the efficiency of the generator.
What is the armature in a DC generator known as?
A commutator, it is used to rectify the induced AC into pulsating DC.
What is the armature in an AC generator called?
In AC, slip rings are used to transfer the system current from the armature windings to be used by the system.
What is the purpose of the brush assembly in a generator?
To transfer the system current from the commutator to the housing wiring?
Describe the construction of the brush assembly in a generator.
Constructed of carbon and held against the commutator with springs.
Describe the construction of the structural parts of a generator.
Consists of an end frame, field frame, and a brush frame, bearings.
What are the three types of DC generators?
Series, shunt, compound.
What is an advantage/disadvantage associated with using a series wound generator?
It has higher output capabilities, it is very hard to control that output.
What is an advantage associated with a shunt wound generator?
It is easier to control output.
What is an advantage/disadvantage associated with using a compound wound generator?
Higher current and voltage output capability and is easy to control, more complex and heavier.
