Super 80 Professional – AOM
ELECTRICAL
Section 11 Page 2
Super 80 Professional – Aircraft Operating Manual
Coolsky, 2018
GENERAL
General
The MD-80 electrical system is designed for
simple and automatic operation. When a
problem occurs, the system automatically
takes the best course of action to maintain
electrical power to the system.
The airplane electrical power system consists
of a 115 volt, 400 Hz AC power generating
and distribution system. For control circuits,
lighting and other load devices requiring DC
power, 28 volt DC power is supplied by
transformer-rectifiers (TR).
Power for the DC system is supplied from two
batteries when the main power distribution
system is de-energized.
A battery charger, powered from an AC
bus, maintains the batteries in a charged
state.
The controls and indicators for the electrical
system are located on the left side of the
overhead panel.
AC power generating system
AC power is normally supplied by any of two
or three AC generators, one on each engine
and one on the auxiliary power unit (APU).
Each generator is rated at 40 KVA maximum
continuous output and is capable of
supplying sufficient power for operation of
essential electric systems in the event of loss
of the other two generators.
For ground operations, an external power
source may be connected to the airplane.
The external power receptacle is located on
the lower fuselage, left side.
The APU generator is mounted directly on
the APU, and driven at a constant speed by
the APU governing system.
Each engine-driven generator is driven
through a constant-speed drive (CSD),
which converts the variable speed output of
the engine to a constant speed.
AC power distribution system
The electrical system is comprised of
independent left and right systems which
are normally powered by the respective
engine driven generator. APU power and
external power may be selected to power
either or both generator buses.
The Ground Service Bus provides power to
those circuits necessary for ground servicing
operations.
An automatic priority system is installed to
determine which power source is used.
Power is automatically applied from the
highest available priority source.
Electrical system priority:
1.
Engine generator
2.
APU generator
3.
External power
4.
AC crosstie relay
Example: If the APU is supplying power to the
bus, and an engine driven generator is
placed on the bus, the APU generator will
automatically be taken off the bus.
The shutdown of a generator will
automatically transfer the load from that
generator to the remaining operating
generator, through the AC crosstie relay.
