DC Electrical Power Distribution
Direct-current power is distributed from the 28-volt primary DC bus and the battery bus.
The 28-volt primary DC bus is powered by both primary AC busses through two transformer-rectifiers.
The primary DC bus, in addition to powering certain equipment, normally powers the battery bus. Failure of one AC generator will not de-energize the primary DC bus. The primary DC bus also is energized when external power is applied on the ground or from the carrier airplane.
The battery bus normally is powered by the primary DC bus. However, the emergency battery can be connected to the battery bus to provide emergency DC power. In addition, external power on the ground or from the carrier airplane can be applied to the battery bus.
A stand-by, 24-volt, emergency battery is available to provide emergency power to the battery bus.
See also:
Electrical Power Supply Controls
Electrical Power Supply System Indicators