Purpose

The electrical power system makes, supplies and controls electrical power. The system has automatic and manual control features. Built-in-test equipment (BITE) and alternate source selection make the system reliable and easy to maintain.

Electrical power has these subsystems:

- Generator drive

- AC generation

- DC generation

- External power

- AC electrical load distribution.

The electrical power system makes and gives AC and DC power to the airplane. The system has automatic controls, manual controls, and protection. The standby AC power and DC power systems give normal and emergency power.

AC Power

The electrical power system has four main AC power sources and one standby power source. These are the main AC power sources and their supply capacities:

- Left integrated drive generator (IDG 1) (90 KVA)

- Right integrated drive generator (IDG 2) (90 KVA)

- APU starter-generator (90 KVA below 32,000 feet/9,753 meters; goes down to 66 KVA at 41,000

feet/12,496 meters)

- External power (90 KVA).

The IDGs and the APU starter-generator supply a 3 phase, 115/200 volts at 400 Hz. The design of the AC

power system prevents two sources to the same load at the same time. The static inverter supplies a single phase, 115v ac output to the AC standby bus.

DC Power

Three transformer rectifier units (TRUs) change 115v ac to 28v dc. The airplane also has these DC power

sources:

- Main battery

- Main battery charger

- Auxiliary battery

- Auxiliary battery charger

The batteries are the backup DC source if other sources do not operate. The standby power control unit (SPCU) controls the distribution of dc power.

Standby Power

With the loss of normal power, the standby power system supplies a minimum of 60 minutes of AC and DC power to systems necessary to maintain safe flight. The batteries supply DC power. The static inverter uses battery power to make AC power. The SPCU controls the distribution of AC and DC standby power.