Piper Navajo PA-31 Service Manual page 728

PIPER NAVAJO SERVICE MANUAL
TEST SPECIFICATIONS (cont.) PRESTOLITE
Rotation
Bi-Directional
Rotor:
Current
Draw (77
°
F) 2.0 to 2.2 amps @ 24.0-volts
Resistance (77
°
F)
11.3 to 11.9 ohms
Output Test (77
°
F): ALU8403 ALU 8421
Volts
26.3
28.4
Amperes Output
10.0
51.0
Field Amperes
2.05
2.05
Alternator RPM
3220 min. 5000 min.
11-37. ALTERNATOR PARALLELING SYSTEM.
11-38.
DESCRIPTION OF ALTERNATOR PARALLELING SYSTEM. The positive
output terminal of each alternator is connected to the aircraft electrical bus through
separate 90-ampere circuit breaker switches. Each alternator has a shunt installed between
aircraft electrical bus and its positive output terminal in order to monitor output current on
an ammeter.
The field circuit for each alternator is wired through a section of a Dual Master Switch
(L or R as appropriate), an auxiliary switch which is ganged to the circuit breaker switch, an
overvoltage relay and a voltage regulator. Field voltage can be manually disconnected from
either alternator by turning off the appropriate section (L or R) of the Dual Master Switch.
Turning both sections of the Master Switch off completely disconnects all electrical power
from the aircraft Bus Bar. Field voltage will be automatically removed from an alternator
whenever its overvoltage relay actuates or its circuit breaker switch trips.
The system has one ammeter installed to measure system currents. The output current
of either alternator may be checked by pressing the appropriate button "LEFT" or
"RIGHT" located below the ammeter on the overhead switch panel. A shunt is installed
between aircraft electrical and the positive terminal of the battery to allow measuring of the
battery charge and discharge current with its ammeter.
An alternator inoperative ("INOP") warning light is provided for each alternator. The
appropriate light will illuminate whenever its respective alternator fails to provide output
voltage.
The 90-ampere circuit breaker switches should not be turned off when their associated
alternator is operating normally. Turning "OFF" one of these switches while it is carrying
current could cause a high voltage transient to occur on the electrical bus with possible
subsequent damage to the semiconductor equipment attached to it.
11-39. DELETED.
Revised: 11/15/82
ELECTRICAL SYSTEM
4C2