2. Electrical System Flashcards
What powers the electrical system and how many volts? (Battery, gens, inverters)
28V DC system, 24V lead acid battery, 2x 250A starter gens (30V regulated to 28.25 +/-0.25V)
DC power is supplied to one of the two operating inverters, which provide 400 hertz, 115V and 26V AC power.
What runs off the hot battery bus?
Engine fire extinguishers, firewall shutoff valves, external power light, entry and cargo lights, clocks.
Also ground comms, rnav memory to older avionics, and standby boost pumps prior to BB-1096.
Also powers the battery relay which, in turn, allows power through to main battery bus, provided battery switch is ON.
How long must GEN RESET be held in down position before back to ON?
Minimum 1 second
Where are the 325A current limiters?
Either side of isolation bus, connected to R and L gen buses.
As long as the current limiters are intact, entire system is supplied by the battery and two generators
What are the conditions for External power?
Aircraft will accept DC power from GPU provided the polarity is correct, and GPU <32V. BAT switch must be on prior to BB-364.
Prior to BB-364 no overvoltage protection.
Prior to BB-1632 (nicad battery) how is a battery overcharge detected?
An amber BATTERY CHG annunciator trigger by an increase in normal current flow
Where is the battery located?
In the right wing center section forward of the main spar
Why does the BATTERY CHG annunciator illuminate after a battery start and what test is done?
The recharge will be very high. As the battery approaches a full charge it will extinguish (a few minutes). Provides an auto self test of the detector and the battery.
Why must battery switch be ON prior to connecting ground power?
Voltage is required to energise avionics master power relays to remove power from avionics equipment
What is located between the the generator buses and the 4 dual fed subbuses?
60A current limiter, 70A reverse current diode, and a 50A circuit breaker (accessible to the crew)
Where are the inverters located?
In the wing center section outboard of each nacelle
Starter limits?
40 sec ON, 60 OFF, 40 ON, 60 OFF, 40 ON, 30 min OFF
Generator load limit ground ops and above 31000ft?
Ground 85% (also observe min N1 for load)
Above 31000ft 88%
What is the initial action if a BATTERY CHG lights illuminates?
Turn the battery switch OFF
How much current should the external power unit be capable of supplying?
1000A and 300A continuous
