Electrical Power Supply - Piper Cherokee Six Service Manual

SECTION X
ELECTRICAL SYSTEM
10-1. DESCRIPTION. The electrical system of the PA-32 is a 14-volt, direct current, single
wire, negative ground system. All electrical equipment is grounded to the metal structure of
the airplane. therefore, the structure takes the place of the second wire. A 12-volt battery is
incorporated in the system to furnish power for starting and as a reserve power source in
case of alternator failure. The battery and alternator are both connected to the bus bar:
from which all the electrical equipment is powered, with the exception of the starter which
receives its power from the load side of the battery. The master switch controls the battery
relay and the alternator field circuit. The master switch must be on before any electrical
equipment will operate. The Cherokee Six can be equipped with the standard position
lights, anti-collision lights, and one landing light located in the nose cowl assembly.
10-2. TROUBLESHOOTING. Troubles peculiar to the electrical system are listed in Table
X-III at the back of this section along with their probable causes and suggested remedies.
The wiring diagrams included in back of this section will give a physical breakdown of the
different electrical circuits used in this airplane.
After the trouble has been corrected, check the entire electrical system for security and
operation of its components.
10-3. ELECTRICAL POWER SUPPLY. The electrical power is supplied by one 12-volt
battery and a 14-volt direct current alternator. The alternator is located on the front lower
right side of the engine and utilizes a belt drive from the engine crankshaft. Many advantages
both in operation and maintenance are derived from this system. The main advantage is that
full electrical power output is available at lower engine RPM.
The alternator has no armature or commutator and only a small pair of carbon brushes.
which make contact with a pair of copper slip rings. The rotating member of the alternator.
known as the rotor, is actually the field windings. The rotor draws only 1/20th of the
current output. Therefore, there is very little friction and negligible wear and heat in this
area. The alternating current is converted to direct current by diodes pressed into the end
bell housing of the alternator. The diodes are highly reliable solid-state devices, but are
easily damaged if current flow is reversed through them.
The alternator system does not require a reverse current relay, because of the high back
resistance of the diodes and the inability of the alternator to draw current or motorize. A
current regulator is unnecessary because the windings have been designed to limit the
maximum current available. Therefore, the voltage control is the only control needed.
ELECTRICAL
SYSTEM
Revised: 7/28/75
PIPER CHEROKEE SIX SERVICE MANUAL
3A14