Electrical Failures; Generator Or Main Bus Malfunctions - Cessna Grand Caravan 208B G1000 Manual

CESSNA
MODEL 208B G1000

ELECTRICAL FAILURES

GENERATOR OR MAIN BUS MALFUNCTIONS

Illumination of the VOLTAGE LOW CAS MSG is a warning that the
power distribution bus voltage is low enough to start discharging the
battery. BUS VOLTS reading is used to verify the low bus voltage. A low
or zero reading of the GEN AMPS confirms that the charge is
insufficient or generator output current is zero. If the GENERATOR
OFF CAS MSG is illuminated, it indicates that the generator contactor
has disconnected the generator from the power distribution bus. The
most likely causes of a generator trip (disconnection) are line surges,
tripped circuit breakers or accidental switch operation. In these cases,
follow the checklist procedures to restore generator operation.
The airplane is equipped with two starter contactors. One is used for
starts on external power and the other for battery starts. If either
contactor does not open after reaching approximately 46% N
amber STARTER ON CAS MSG will remain illuminated. In most cases
when this occurs, the generator will not transfer to the generator mode,
and the GENERATOR OFF CAS MSG will remain illuminated. Under
these conditions, it will be necessary to shut down the engine using
checklist procedures and correct the malfunction prior to flight.
Illumination of the Amber GENERATOR AMPS CAS MSG indicates 1
of 2 conditions:
1. The current load on the generator is above its rated value for
that flight condition. The pilot should reduce the electrical load,
or change flight conditions as noted in the 300 Amp Starter
Generator supplement.
2. The reverse current protection of the GCU has failed. If the GEN
AMPS is below -10 amps the pilot should disconnect the
generator
GENERATOR Switch.
The electrical power distribution system consists of a primary power
distribution bus in the engine compartment which receives power from
the battery and the generator, and two (No. 1 and No. 2) main power
buses located in the circuit breaker panel. The main buses are each
connected to the power distribution bus by three feeder cables. Each
feeder cable is protected by a fuse link and a circuit breaker. This
multiple feeder system provides automatic isolation of a feeder cable
ground fault. If one of the three 30-amp feeder circuit breakers on either
bus opens, it should be assumed that a feeder cable ground fault has
been isolated, and attempted resetting of these breakers prior to
troubleshooting is not recommended. The electrical load on the
affected bus should be maintained below the remaining 60-ampere
capacity.
FAA APPROVED
208BPHBUS-01
from the electrical
EMERGENCY PROCEDURES
system by
U.S.
SECTION 3
, the
g
tripping the
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