AIRFRAME ELECTRICAL SYSTEMS QUESTIONS & SOLUTIONS

AIRFRAME ELECTRICAL SYSTEMS
QUESTIONS & SOLUTIONS
Left-Hand Rule - ANSWER Thumb = conductor, first finger = flux forward and second
finger = Induced EMF

DC Generator Construction - ANSWER Field Frame, Armature, Commutators, and
Brushes

Field Frame - ANSWER Completes the magnetic circuit between the poles, and acts as
a mechanical support for the other parts

Pole Shoes - ANSWER bolted to the inside of the frame and are usually laminated to
reduce eddy current losses and concentrate the lines of force produced by the field
coils.

Armature - ANSWER The rotating part of an electrical generator.

Armature coils in a drum type armature the coils are usually held in the slots by -
ANSWER wooden or fiber wedges.

Coil ends of the armature are brought out to - ANSWER individual segments of the
commutator.

Commutators - ANSWER devices used to convert direct current (DC) to alternating
current (AC)

Brushes - ANSWER The contact points connected to a current source and the
commutator of a motor

Pig tail - ANSWER Short piece of electrical cable with connector plugging device at both
ends.

Three types of DC Generators - ANSWER Series-Wound, Shunt-Wound and
Compound Wound

Shunt-Wound - ANSWER Where the field winding in parallel with armature winding

Compound-Wound - ANSWER Field and armature connected to each other by both
series and parallel circuits

Three different types of Compound-Wound - ANSWER Flat-Compound, Under-
Compound, and over-compound

, Starter Generator Consist of? - ANSWER two sets of windings and one armature
winding. After done starting the engine, switches back to generator mode.

Armature Reaction - ANSWER The bending and twisting (distortion) of the main
magnetic field caused by the magnetic field of the current in the armature.

How to correct Armature Reaction - ANSWER Brushes are set so that the plane of the
coils being shorted is perpendicular to the distorted magnetic field. Moving brushes
forward in direction of rotation. (brushes to the neutral plane, or plane of commutation).

Interpoles - ANSWER counteract some of the effects of field distortion when the speed
and load of the generator are changing constantly. Placed in-between the main poles.

Rheostat - ANSWER set to increase the resistance in the field circuit. less current flows
through the field coils and the strength of the magnetic field decreases.

Less Voltage is induced into the armature then.... - ANSWER Generator output
decreases

Solenoid - ANSWER A coil of wire that produces a magnetic field when carrying an
electric current. ex: electrically connects or removes the field rheostat from the circuit as
the voltage varies.

Three-Unit Regulator components - ANSWER current limiter, reverse current cutout,
and a voltage regulator

Current Limiter - ANSWER limits the generator's output current

Reverse-current cutout - ANSWER Disconnects the battery from the generator when
the GENERATOR output is LOWER than the BATTERY output.

If the reverse-current cutout would not disconnect the battery then.. - ANSWER It would
discharge through the generator armature when the generator voltage falls below that of
the battery. The battery attempts to drive the generator as a motor.

Voltage Regulator - ANSWER A device that maintains a constant voltage level for either
AC or DC electrical energy.

Carbon-pile voltage regulator - ANSWER A type of voltage regulator used with large
aircraft generators. Field current is controlled by varying the resistance of a stack of thin
carbon disks. This resistance is varied by controlling the pressure on the stack with an
electromagnet whose force is proportional to the generator output voltage.

DC generator is unable to keep an aircraft battery charged, and if the ammeter does not
show the proper rate of charge... - ANSWER First check the aircraft electrical system
associated with the battery and generator.