ELECTRICAL SYSTEM Flashcards
Alternating Current (ac) is the primary source of electrical power and can be supplied from:
main generators (115v ac)
the APU generator (115v ac)
external power
The two main generators are driven by what?
MGB
Dc electrical power is supplied by either:
two converters (convert 115-volt ac power to 28-volt dc power)
24-volt dc Nickel-Cadmium (NICAD) battery
Generator Control Units (GCUs) do the following:
connects each respective generator to the ac electrical bus system
regulates generator output
protects system components and monitors voltage level and frequency
GCU and Nr relational values and effects
With WOW, if Nr droops below 94 percent, the GCU removes the main
generator electrical input from the entire ac power distribution system.
In flight, underfrequency protection is disabled and the generators will
remain online until the Nr decreases to approximately 80 percent.
A minimum of 97 percent Nr is required for the GCU to reconnect the
generators to the ac electrical distribution system.
Five electrical buses in the ac electrical distribution system:
No. 1 ac primary bus
No. 2 ac primary buss
ac essential bus
ac Secondary bus
ac Monitor bus
Five buses in the dc electrical distribution system:
No. 1 dc primary bus
No. 2 dc primary bus
dc essential bus
Battery bus
Battery Utility bus
How many converters are there, what powers them, and what do they do?
Two converters
powered by the No. 1 and No. 2 ac primary buses
supply 28-volt dc power to the dc bus distribution system
The 24-volt dc battery, located in the copilot seat well, is installed to:
start the APU
power the Battery Utility bus
provide an emergency source of dc power
Battery Analyzer/Conditioner monitors:
battery system for fault conditions
battery charge
internal temperature
cell conditions
provides a battery-charging capability
If the battery analyzer/conditioner senses a fault, it will:
automatically disconnect the dc loads from the battery, or the battery
from the charging circuit, as appropriate.
When does the battery charge?
whenever ac power is available and the
BATTERY switch is ON
If a single dc converter fails what happens?
the operating converter will pick up the load of the buses powered by the failed converter via a dc bus tie
If both dc converters fail what happens?
both dc primary buses are dropped and both FDs and MDs will be lost.
The battery will provide emergency electrical power to the___ bus (if
the BATT switch is ON) and the __ _____ bus (if the battery is above a ___ percent charge). With an ___ percent
charge, normal battery life is ______ for day operations and _____ for night operations.
Battery
dc essential
35%
80%
11 minutes
9 minutes
