Electrical System Flashcards
Sealed Lead Acid Battery (SLAB)
24 Volts DC located in the left forward electrical compartment.
Provides 24 V to the battery bus and if the batt switch is on it will also provide power to the No 1 and 2 essential buses.
Gang bars
Also known as the AC bus-tie circuit breakers. Purpose also is to isolate the respective system and prevent a bus-tie to the other side
Main AC
Generators
They are the primary source of AC power.
Located on the aft
transmission and cooled by the aft transmission main lubrication system.
Each generator rated for up
to 40 KVA. Supplies 115/200 volt, 3 phase, 400 Hz power to the No 1 and 2 AC buses. At 100% Rotor RPM the frequency reaches 400 hz.
If rotor RPM is between 82%
and 85% the frequency will drop to 325- 335 Hz and the Generator Control Unit will remove generator power
from its respective bus within 3 to 7 seconds.
Permanent Magnetic Generator (PGM)
Inside the main generators and provides the Rotor RPM speed signal
Main Generator
Control Units
(GCU)
Monitor for over-voltage, under-voltage, under-frequency, and feeder faults (short circuits).
A feeder fault is when there is a discrepancy between power being produced by the generator and what is being sampled at the PDP (usually due to a short circuit).
Located in the Forward left
electrical compartment and behind the bench seats near the main cabin door on the number 2 side.
APU Generator
Mounted on the APU accessory and reduction drive assembly and driven
by the APU. Supplies AC power on the ground and certain emergencies.
Air cooled by a built in fan and
capable of producing up to 20 KVA.
Besides the lower power output, essentially the same as the main AC generator.
The current leaving the
generator measured by current transformers (2nd picture).
It is the secondary source of AC Power.
APU GCU
In the forward right electrical
compartment and the same as the main GCUs but it is black instead of
white.
Transformer
rectifiers (TRU)
Convert AC current into DC current for the No 1 and 2 DC buses.
Located in the front right and left electrical compartments.
They are the primary source of DC power.
Cooled by built in fan that takes air from the cabin.
Aviation Ground Power Unit
(AGPU)
Supplies power on ground. The last source of AC power
Reverse current
cutouts (RCCO)
Protect DC electrical system by not allowing current to flow the opposite direction.
Also active the RECT OFF cautions.
Contactor Relays
Contactor relays connect electrical power to the number one and number 2 AC buses from one of four possible sources of AC
electrical power.
Priority of Power
AC: Main Gen > APU Gen >
External
DC: Transformer Rectifiers (28V) > external (28V) > battery (24V)
