BRUSH HOLDER:
Device that retains multiple brush assemblies and is comprised of a holder, contacts, and
terminals.
CONTINUITY:
The continuous path for the flow of current in an electrical circuit.
COOLING COVER:
Device attached to the alternator to provide cooling air from an external source. May be
provided with alternator or required by the airframe manufacturer. (Also known as the “Blast Tube”, referring to
ram air cooling source.)
EMI:
Electro Magnetic Interference. A disturbance in the radio-frequency spectrum that is generated by an
external source that affects electrical devices or circuits by electromagnetic induction, electrostatic coupling, or
conduction.
FRONT HOUSING:
Part of the external housing which contains the components of the alternator. This end
has structure typically used for mounting. It may also be referred to as the Drive End Housing or D.E.
INSULATOR:
Component that does not allow electricity to flow through it easily. Insulators do not allow
electricity to flow through them easily because the electrons in their atoms do not move easily from atom to
atom.
MULTIMETER:
Device for the measurement of voltage, current, or resistance.
LEAKAGE:
Dissipation of voltage or current from a component or connection.
OPEN:
Electrical term for a complete disruption of a conductive path in an electrical circuit. Will read infinite
resistance.
PEAK INVERSE VOLTAGE:
(PIV) The maximum rated value of a AC voltage acting in the direction opposite
to that in which a device is designed to pass current.
PHASE:
The position of a point in time (instant) on a waveform cycle. A complete cycle is defined as 360
degrees of phase. Phase can also be an expression of relative displacement between or among waves having
the same frequency. In our case the alternator is three phase or 120 degrees separation.
POLARIZE:
To induce polarization i.e., the partial or complete polar separation of positive and negative elec-
tric charge in an electrical system.
REAR HOUSING:
Part of the external housing which contains the components of the alternator. It may also
be referred to as the Slip Ring End or S.R.E.
RECTIFIER:
An electrical circuit used to convert AC into DC current. The rectifier is an arrangement of diodes
that causes the current to flow in only one direction.
RFI:
Radio Frequency Interference. Electromagnetic energy in the radio-frequency spectrum. Electrical inter-
ference may be created by poor slip ring/brush connection, defective rectifiers, or other poor connections. This
is a normal by-product of electrical generators.
ROTOR:
Rotating electro magnet used to create a magnetic field. SLIP RING: Device which provides a sliding
contact surface for the brush assemblies. The slip rings are smooth surface copper “rings” pressed onto the
rotor shaft.
SHORT:
Common term for a connection which has no or very little resistance as seen on an Ohmmeter in an
electrical circuit. Typically an undesirable condition with respect to grounded elements.
STATOR:
A stationary set of conductors wound in coils on an iron core.
TEST BENCH:
Device so constructed as to allow testing of the alternator or component parts.
TERMINALS:
Studs, screws or other devices that provide connections for electrical power.
THROUGH BOLT:
Special bolts which connect front and rear alternator housings.
Aircraft Alternator
Maintenance Manual
ES1031
24-30-01
Rev. B: 20 Apr. 2022
Page: 1-5
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