The APU GCU monitors the frequency of the APU generator, which is driven at a constant 12,000 rpm by the APU. If the APU generator speed is out of limits, this condition is seen by the APU GCU as a frequency fault.
If you have only one AC power source available in the air, the galley will be available.
If you have only one AC power source available on the ground, the galley will be available.
An essential TRU can be switched to power a main DC bus.
Each IDG is controlled by a generator control unit (GCU). One of the GCU functions is:
Other than by pulling and resetting the CB, how can you reset a generator control unit (GCU)?
There are ____ generator control units (GCUs) located in the electronic equipment racks (EERs).
Each generator control unit operates in conjunction with its respective IDG, APU generator, and cockpit overhead panel to supply system protection and control functions, and built-in test capability for the AC electrical generating equipment.
Which bus power control unit (BPCU) controls AC external power?
The aircraft is equipped with a standby electrical power system that is powered by a hydraulic motor generator (HMG). The HMG provides AC power if:
One IDG is mounted on the rear of each engine reduction gearbox. Each IDG consists of a hydromechanical constant-speed drive (CSD), mounted:
The CSD portion of the IDG converts variable-input speed from the engine reduction gearbox to a constant speed to drive the generator portion of the IDG. The generator is rated at 40 KVA and provides three-phase, 400-Hz, 115-VAC power.
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The ground service bus can receive power from:
A main TRU can be provided with AC power from the off-side main AC bus, i.e., left main TRU powered by the right main AC bus.
The battery chargers will not charge the batteries if they are below _____ amps.
The GCUs are physically identical and interchangeable.
How many transformer rectifier units (TRU’s) are normally operating?
Each battery charger has a TR mode capable of providing:
The engine fire and fuel shutoff switches provide inputs to the GCU that disabled the generator operation at:
DC bus priority logic for the main DC buses are as follows:
The external power on/available switch is a latching switch located on the COP. If external power, AC or DC, satisfies the power-ready requirements, the available (AVAIL) light will illuminate.
There are two 21-cell, 24-VDC, 53-amp-hour nickel-cadmium batteries installed in the aft equipment (tail) compartment. These batteries provide basic DC power to:
The right main battery has additional functions on the ground. It is used to power the ground service bus if it is not powered by right main DC bus or external DC power, or operate the airstair door.
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When operating on the hydraulic motor generator (HMG) the aux TRU can power both the left and right ESS DC buses simultaneously.
Transformer rectifier units provide the primary source of DC power for the main and essential DC-powered systems in the aircraft, with the exception of the APU and auxiliary hydraulic pump.
The TRU L MAIN switch, when depressed, energizes the LMTAC contactor. This allows the left main TRU to be powered by the:
The switch will illuminate amber R AC to annunciate the TRUs input power source.