Saab 340B, Руководство по эксплуатации

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ELECTRICAL
Description
Aircraft Operations Manual
5.1
PAGE 1
Jun 01/19
1. GENERAL
The electrical power system is divided into four sep-
arate parts, namely:
− A 28 V DC system, powered either from two en-
gine driven generators, from two batteries or
from an external power source, Fig. 1
− Fig. 8.
This system is split in a left and a right system,
each with one generator and one battery.
− An emergency power system, powered from the
ordinary DC system or from an emergency power
battery, Fig. 1
− Fig. 8.
− A frequency controlled 115/26 V AC 400 Hz sys-
tem, powered from the DC system through a
main or a standby (26V AC only) inverter,
Fig. 1
− Fig. 8.
− A “wild” frequency AC system, powered from two
engine
− driven generators and used for ice
protection only, Fig. 10.
Distribution of DC power is effected through a left
and right power distribution unit to the respective
GEN BUS, MAIN BUS, BAT BUS, AVIONIC BUS,
ESS BUS, MAIN START BUS and AVIONIC
START BUS. In addition, the ESS AVIONIC BUS,
EMERGENCY BUS and EMER AVION BUS are
connected to the left power system while a UTILITY
BUS is connected to the right power system. There
is also a HOT BAT BUS connected to each battery.
The left and right power systems are tied together
by a bus tie relay thereby enabling a single battery
or generator to supply both power systems.
The emergency power system consists of the pre-
viously mentioned EMERGENCY BUS and EMER
AVION BUS. These buses are, in addition to the
normal power supply, supplied from an emergency
battery for a limited time as a last power resource.
The AC system consists of a L and R INV BUS
115V AC plus a L and R INV BUS 26 V AC. The AC
buses are normally powered through the main in-
verter from the L MAIN BUS. The L and R INV BUS
26V AC may also be powered through the standby
inverter from the R MAIN BUS.
“Wild” frequency AC, used for ice protection only, is
supplied from two generators, driven by the respec-
tive propeller gearbox, to the L and R GEN BUS
115V AC. Either AC generator can supply both
buses through the use of a load transfer relay. Each
engine air intake anti
− icing is supplied from respec-
tive AC generator.
Control and monitoring of the electrical system is
performed from the overhead panel.
2. MAIN COMPONENTS AND SUBSYSTEMS
2.1 DC Starter Generator
Normal power supply is from the two 400 ampere,
combined starter/generators located one on each
engine accessory gearbox. They deliver 28 V DC to
the respective:
− GEN BUS and BAT BUS via the generator relay.
− MAIN BUS via the generator and main bus re-
lays.
At engine start, a speed switch in the starter/gener-
ator senses the RPM for the GCU which controls
the disengagement of the start cycle.
The generator drive shaft has a shear point which
will separate the generator drive shaft from the ac-
cessory drive gear in case of high mechanical over-
loading.
On the ground the starter/generator is cooled by an
integral fan and when airborne ram air is used for
cooling.
A thermoswitch will cause a GEN OV TEMP light in
the overhead panel to come on if a generator is
overheated (150

C).
The operation of the starter/generator is controlled
by the respective generator control unit (GCU).
2.2 DC Generator Control Unit (GCU)
Two separate but identical GCU’s are provided for
the two generators. A GCU furnishes its associated
generator with field excitation and voltage regulation
for control and protection of the DC system against
faults in the generation system. The GCU also con-
trols the engine start cycle and disengages the
start/generator at 55% Ng.
If a generator parameter is not correct, the GCU
de
− energizes the generator by opening the field
relay, and disconnects the generator from the GEN
BUS by opening the generator relay.