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The electrical power distribution system consists of four distribution boxes: -Two of the four electrical distribution boxes are direct current power centers (DCPC). These are located in the aft equipment bay of the aircraft. They are fed by the power sources listed above and their function is to switch elec-trical power to the distribution buses and then distribute this power to loads in the aft fuselage of the aircraft -The other two electrical distribution boxes are secondary power centers. They are located in the equipment rack in the front fuselage of the aircraft and are fed by the distribution buses of the DCPCs. They distribute electrical power to the loads in the front fuselage of the aircraft -Two circuit breaker panels are located in the cockpit. They are fed by the distribution buses of the secondary distri-bution centers and distribute electrical power to loads which require pilot access to the associated circuit breaker. -The electrical system is electrically and physically segregated into two channels. External DC power and the APU generator are arranged to connect to these two channels COMPONENTS AND OPERATION ENGINE AND APU GENERATORS Two engine driven generators, one on each engine accessory section, provide the normal source of 28 volt power to the airplane. A third identical generator is installed on the APU. All three generators are air cooled and include an integrated fan. The engine-driven generators automatically come online after the engines are running, the GPU is disconnected, and the EXT PWR switch on the electrical control panel is depressed, changing the annunciation from ON to AVAIL. The gen-erators are limited to 12 kVA (400 amp) and the nominal output voltage is 29.5 volts. When at least two generators are online, the bus tie is normally open. The left generator recharges the left main battery, and the right generator recharges the right main battery. The generators supply DC power to all DC powered equipment on the airplane under normal conditions. EXTERNAL POWER |
