Generator System - Piper PA-24 Comanche Service Manual

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PIPER COMANCHE SERVICE MANUAL
SECTION IX
ELECTRICAL SYSTEM
9-1.
General.
9-2. Electrical power for the Comanche is supplied by a 12-volt. direct current. single wire. negative ground
electrical system. A 12-volt battery is incorporated in the system to furnish power for starting and a reserve
power source in case of generator or alternator failure. An external power receptacle can be provided as
optional equipment in the fuselage to permit the use of an external power source for cold weather starting.
On the PA-24-180 and PA-24-:!50 models. a 35-ampere or SO-ampere generator is installed. With the
generator is a regulator assembly. composing of a voltage regulator. and current regulator to prevent over-
loading of the battery and electrical circuits. Also. with the regulator is a reverse current cutout to prevent the
generator from being motorized. by the battery. when the generator output drops below the battery voltage.
On the PA-24-260 and PA·24-4QO models. a 70-ampere alternator is installed.
It
is controlled by a
voltage
regulator within the field circuit to control field voltage. Also. in the field circuit is a 5-ampere thermal circuit
breaker. master switch. radio noise filter and an over-voltage regulator. The output circuit consists of a radio
.noise filter and a 90-ampere magnet circuit breaker ganged to the 5-ampere circuit breaker in the field circuit.
The generator or alternator is located on the front lower right side ofthe engine and utilizes a belt drive
from the engine crankshaft. The generator voltage regulator is located on the engine firewall and the alternator
voltage regulator and relay is located within the aft section of the fuselage.
Electrical switches are located on the left lower side of the instrument panel. Circuit breakers for the
individual circuits are mounted in a cluster below the left side of the instrument panel.
CAUTION
The alternator circuit breaker should not be opened under any
circumstances. other than an emergency. while the engine is
running.
Standard lighting on the Comanche are navigation lights. landing lights. one on the outboard leading
edge of each wing. cockpit light and instrument spot lighting. As optional equipment. a rotating beacon is
mounted on top of the fuselage and individual instrument lights.
9-3.
Generator System.
9-4.
General.
The generator supplied with the Comanche is of the two brush. shunt type and is controlled
by a regulator operating on the principal of inserting resistance into the generator field circuit to cause
a
reduction of generator voltage and current output. The best assurance of obtaining maximum service from
the generator with
minimum
trouble is to follow a regular inspection and maintenance procedure.
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ISSl'ED: 8/18/72
3A12
ELECTRICAL SYSTEM