# Engine Electrical part3

refabeco's version from 2015-08-10 19:58

## Section

Question Answer
type of insulation is used between the commutator segmentsThe ends of the conduit should be flared to prevent damage to the insulation of the wire.
define armature reactionAt the lowest point in the conduit run.
What device produces the electrical energy to operate most of the electrical equipment in modern aircraft?Generators driven by the engines, these may be either AC or DC.
What happens in a conductor when it cuts across lines of magnetic flux?A voltage is induced in the conductor.
What determines the amount of induced voltage generated when a conductor cuts across a magnetic field?The speed at which the conductor moves through the lines of magnetic flux, and the strength of the magnetic field.
What type of voltage is produced when a loop of wire is rotated within a magnetic field?An alternating voltage
What type of voltage will be produced at the brushes if the ends of the loop of wire rotating within a magnetic field are connected to a split-ring type commutator?Direct current
What is the name of the rotating part of a DC generator which contains the output coils and the commutator?The armature
What is the purpose of a commutator on a DC generator?The commutator converts the alternating current in the armature windings into direct current before it is. fed into the aircraft circuits.
What is another name for commutation?Rectification
What should the voltage difference be between two commutator segments as they are shorted by a brush?The voltage should be zero between the adjacent commutator segments at the position they are contacted by the brush.
What may be done in the design of a DC generator to reduce the amount of ripple in its output?Increase the D;Umber of loops or coils in the armature
What determines the output voltage of a DC generator?The number of turns of wire in each loop, or coil, the total flux between each pair of poles, and the speed of rotation of the armature.
What is the basic difference between a DC generator and an AC generator.The basic difference is in the way the electricity is taken from the armature. In a DC generator it is taken out through brushes and a commutator, and in an AC generator it is taken out with brushes from slip rings.
What are the three major assemblies in a DC generator?The field frame, the rotating armature, and the brush assembly.
What are two functions of the field frame of a DC generator?It completes the magnetic circuit between the poles, and it acts as a mechanical support for the rest of the generator.
Why are the magnetic field poles of a DC generator normally made of laminated soft iron?Laminated soft iron reduces the heat losses caused by eddy currents flowing in the pole pieces
Of what material are the field frames of a DC generator normally made?High quality magnetic soft iron
Why do DC generators normally use electromagnets rather than permanent magnets for their fields?Electromagnetic strength may be varied to control the generator output. Also, permanent magnets having enough strength to produce the required voltage would have to be unnecessarily large.
What two sources of current may be used to magnetize the field-poles in a DC generator?Excitation current may be obtained either externally, or from the output of the generator itself
Why is it important that the field pole shoes be as close to the rotating armature as possible?An air gap acts as a high reluctance path for the magnetic flux; therefore, the pole shoes should be as close to the rotating element as it is possible to prevent loss of magnetic flux
Why is the core of the armature of a DC generator made of laminated soft iron?The core is made of laminated soft iron to minimize the iron losses in the form of circulating eddy currents.
How are the coils held in the slots of a drum type armature?The coils are locked into the slots with wood or fiber wedges.
Of what material are commutator segments made?Hard drawn copper
What insulating material is used to separate the commutator segments in a DC generator?Thin sheets of mica
Of what material are DC generator brushes made?High grade carbon
Name three types of DC generators.Series-wound, shunt-wound, and compound-wound.
Describe the field coils of a series-wound DC generator.Series-wound field coils have a few turns of heavy wire wound around laminated pole shoes, and are in series with the armature and the load.
What happens to the output voltage of a series-wound DC generator as the load current increases?As the load current increases, the output voltage increases.
How may the output voltage of a series-wound generator be controlled?A high current rheostat may be placed in parallel with the series field windings to vary the magnetic strength of the field anq control the output voltage.
What type of DC generator is most commonly used in aircraft electrical systems?Shunt-wound generators
What is meant by a shunt-wound DC generator?A shunt-wound generator has its field windings in parallel with the armature.
Describe the field coils of a shunt-wound DC generator.Shunt-wound field coils have many turns of relatively small wire wound around laminated soft iron pole pieces.
Wire size may be determined by using a?Wire Gage
One of the factors that must be considered when selecting the size of wire for transmitting and distributing electrical power isLarger the diameter less resistance
What has more conductivity, copper or aluminum?Copper
When speaking of conductor insulation, insulation resistance is the resistance to current leaking through whatinsulation material
All wires should be routed to protect them fromChaffing and high temp
All wires in the vicinity of a battery should be inspected?Frequently
Wires discolored by battery fumes should beReplaced
On/Off 2 position electrical switches should be installed ..so that the on position is upward or forward
Cable clamps of the right size for the cable they are being installed on should be used to avoidPinching
All wire groups or bundles should be tied or supported with cable clamps, no more then how many inches apart?12 inches
All wires or cables should be cut to the length specified byDrawings & Wire Diagrams
Aluminum wiring is being increasingly used over copped because of its weight advantages, however constant bending of aluminum causesWork hardening in the metal making it brittle
Terminal lugs should be installed on terminal blocks in such a manner that they arelocked against movement in the direction of loosing
Bonding is the ____ connecting of 2 or more conducting objects?Electrical
Grounding is the electrical connecting of a ____ object to the primary structure for the return of current.Conducting
Canon plug connectors class A,B,C and D are made of aluminum, what is class K made of?Steel
When installing additional electrical equiptment that consumes electcial power in aircraft the total _______ must be safely controlled or managed within the rated limits of the affected components of the aircrafts power supply.Total electric load
Where rate reduction can be achieved or electrical controls can be simplified, switching devices known as what are used?Relays