Overhead Electrical Flashcards
What does the Standby Power switch do in OFF, AUTO, and BAT?
OFF: Standby Power not available, Main and APU standby busses disconnected from all power sources
AUTO: Allows Main and APU standby busses to be powered by available sources.
BAT: (Battery switch on) Main and APU battery busses are powered by respective hot battery bus. Main and APU battery chargers are disabled. Standby Busses powered through respective standby inverters powered by respective hot battery busses. MX USE ONLY
What does the Battery switch do when ON and OFF?
ON: Main and APU Batteries available as backup power for respective battery and standby busses
OFF: Disconnects Main and APU batteries from respective battery and standby busses.
What does an OFF light in the Utility L or R switch mean?
Power is removed from respective ELCUs.
Related utility power switch is off.
*Will not illuminate during load shed
What does selecting L or R Utility Switch ON and OFF do?
Power is removed from respective ELCUs.
Related utility power switch is off.
*Will not illuminate during load shed
What happens when an EXT PWR or APU GEN switch is pushed with an AVAIL light illuminated?
1 power is connected to AC system, ground handling bus is still powered.
New power source will kick off respective side power old power source. SSB will open to split synchronous bus if both a #1 and #2 source are selected at the same time.
What does an AVAIL light in an APU GEN switch mean?
APU Generator power quality is acceptable
Ground Handling Bus or Main Deck Cargo Handling bus is powered with #1 or #2 avail respectively if EXT PWR is not connected
What does an AVAIL light in an EXT PWR switch indicate?
Power is plugged in and quality is acceptable.
Ground Handling Bus or Main Deck Cargo Handling bus is powered with #1 or #2 avail respectively.
With both EXT PWR and APU GEN AVAIL lights illuminated, what is powering the ground handling bus and main cargo handling bus?
EXT PWR 1 is powering the Ground Service Bus.
EXT PWR 2 is powering the Main Deck Cargo Handling Bus.
What does an ON light mean in an EXT PWR or APU GEN switch?
ON: Power source is connected to the AC electrical system.
Button press with the ON light illuminated disconnects power source from AC system and indication returns to AVAIL
What happens when a BUS TIE switch is pushed to the AUTO position? What happens in the OFF position?
AUTO: Arms automatic AC bus tie circuitry and closes related DC isolation relay (DCIR)
OFF: Opens BTB (Bus Tie Breaker) and DCIR.
Resets fault logic circuitry
What does the ISLN light in the BUS TIE switch mean?
BTB (Bus Tie Breaker) is open
AC Bus is isolated from the synchronous bus
What happens when the generator DRIVE DISC switches are pushed?
Disconnects respective IDG (physically) from engine when above idle speed
Opens related GCB
*Ground Maintenance action required to reconnect
What does a DRIVE light illuminated in the DRIVE DISC switch mean? Does anything happen automatically?
High generator oil temperature, or
Low generator oil pressure, or
GCB open due to uncorrectable generator frequency fault.
High oil temperature will automatically physically disconnect the generator
What does the GEN CONT switch do in the ON and OFF positions?
ON: Arms GCB to close when generator power is of acceptable quality
OFF: Opens generator field and opens the GCB.
Resets fault control logic circuitry.
Isolates the generator from the respective AC Bus (because the GCB is open)
What does an OFF light in a Generator Control switch mean?
GCB (Generator Control Breaker) is open
