by jerome meriweather
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Standby Power Selector
- OFF - Disconnects the main and APU Standby buses from all power sources.
- AUTO - Allows the main Standby bus to be powered automatically from AC bus 3.
- BAT - Powers the main and APU Standby buses from their respective batteries through their hot battery busses and Standby inverters.
Utility Power Switches
- ON - Each switch powers two galley and two utility buses if no load shedding signal is present.
- OFF - Disconnects the two galley and two utility buses from AC power and reset fault circuitry.
- Lights - Indicate that one or more buses are unpowered, either automatically by protective circuits or by turning the switch off.
- OFF - Closes APU bleed air valve, initiates automatic shutdown sequence and resets fault detection logic.
- ON - APU operating position.
- START - Initiates automatic Start sequence. Spring-loaded from START to ON.
- ON - Enables the main and APU batteries to provide backup power to the main and APU battery buses and the main and APU standby buses.
- OFF - Disconnects main and APU batteries from respective battery buses.
- OFF Light - Indicates the BATTERY switch is OFF.
BUS TIE Switches
- AUTO - Allow Bus Tie breaker and respective DC isolation relay to close automatically when system logic permits.
- OFF - Open the Bus Tie breaker and respective DC isolation relay.
- ISLN Lights - Indicate the respective AC Bus is isolated from the Tie Bus as the Bus Tie breaker has opened due to a fault,
or the switch is off.
GEN CONT Switches
- ON - Close Generator field and allow the Generator control breaker to close automatically when system logic permits.
- OFF - Open Generator field and Generator control breaker. Reset fault trip circuitry.
- OFF Lights - Indicate Generator control breaker is open.
Drive DISC Switches
Disconnect the IDG from the engine. Can only be reconnected on the ground.
- Lights - Indicate generator Drive has low oil pressure or excessive oil temperature.
EXT PWR Switches
Open or close the External power contactor if the AVAIL light is on.
- ON Lights - Indicate external power contactor is closed.
- AVAIL Lights - Indicate External power is plugged in and the voltage and frequency are within limits.
APU GEN Switches
Open or close the auxiliary power breaker if the AVAIL light is on.
- ON Lights - Indicate APU power breaker is closed.
- AVAIL Lights - Indicate output voltage and frequency of the APU generator are within normal limits.