AC Electrical Power Distribution

Two AC generators supply 200/115-volt, 400-cycle, three-phase AC power to the two primary AC busses. Each generator is driven through a gear train by an auxiliary power unit (refer to "Auxiliary Power Units"). Two 26-volt AC busses are powered by the No. 2 primary AC bus. Automatic frequency control and voltage regulation are provided for the AC generators.

AC Generators

Each AC generator is driven through a gear train by an auxiliary power unit and supplies 200/115-volt, 400- cycle, three-phase AC power to its respective primary AC bus. Failure of an APU causes failure of the AC generator it drives. If one AC generator fails for any reason, the other AC generator automatically supplies power to both primary AC busses. If either generator drops "off the line" because of a momentary malfunction, it can be reset "onto the line".

Primary AC Busses (200 volts)

The No. 1 primary AC bus normally is powered by the No. 1 AC generator; the No. 2 primary AC bus, by the No. 2 AC generator. However, if either generator fails, the remaining generator will power both primary AC busses. External power, on the ground or from the carrier airplane, will power the primary AC busses, but only when neither AC generator is on.

26-Volt AC Busses

The two 26-volt AC busses are powered through two parallel transformers by the No. 2 primary AC bus. The 26-volt busses are powered as long as either AC generator is operating. In addition, when external power is applied to the airplane on the ground or from the carrier airplane (and both AC generators are off), the 26-volt busses are powered.