Standby Power System

Normal Operation

The standby system provides 115V AC and 24V DC power to essential systems in the
event of loss of all engine or APU–driven AC power. The standby power system consists of:

  • Static inverter
  • AC standby bus
  • DC standby bus
  • Battery bus
  • Hot battery bus
  • Switched hot battery bus
  • Main battery

Option - Dual battery

  • Auxiliary battery.

During normal operation the guarded standby power switch is in AUTO and the battery
switch is ON. This configuration provides alternate power sources in case of partial power
loss as well as complete transfer to battery power if all normal power is lost. Under normal
conditions the AC standby bus is powered from AC transfer bus 1. The DC standby bus is
powered by TR1, TR2, and TR3; the battery bus is powered by TR3; the hot battery bus
and switched hot battery bus are powered by the battery/battery charger.