With the battery switch off and no GPU hooked up, these buses are powered. When any of the following doors are opened, the Ground Handling Bus is energized through the Battery Transfer Relay. 1. 2. 3. 4. Cargo Door Access Panel Refueling Panel Main Cabin Door Auxiliary Hydraulic Pump Push Button is depressed. HOT EMER BAT BUS + HOT MAIN BAT BUS - + Hot Emergency Battery - Hot Main Battery GND HDLG BUS BTR If you walk into the cockpit and observe a GREEN AVAIL light on the main electrical panel, these buses are now powered. AC BUS 2 AC BUS 1 STBY BUS INV 1 INV 2 EMER BUS ESS BUS OFF ON When the GPU is plugged in, the External Ground Handling Relay closes taking priority over the Bus Transfer Relay. The BTR then opens. HOT EMER BAT BUS HOT MAIN BAT BUS OVRD BAT EMER BAT CHG MAIN BAT CHG 0 1 DC BUS 1 DC 2 DCH + - + Hot Emergency Battery 1 Hot Main Battery DC BUS 2 2 CH BAT SEL EMERG MAIN BTC EGHR SHED DC SVCE/UTLY BUS SHED DC GEN 1 EXT PWR AVAIL DC GEN 2 - GND HDLG BUS BTR EXTERNAL POWER EMER LT CALLS PASS LAV SMOKE CAPT LAV CARGO GND SVCE BUS DC AC If the DC SERVICE BUS push button is depressed on the flight attendant panel, then the DC SERVICE BUS is powered through the Service Bus Transfer Relay. ON GALLEY LAV LAT PASS DIM UPR PASS AFT READ LT ENTR CARGO VENT HOT EMER BAT BUS The GPU is now powering the Ground Handling Bus and the DC Service Bus. + HOT MAIN BAT BUS - + Hot Emergency Battery DC SVCE BUS - Hot Main Battery SBTR EGHR GND HDLG BUS BTR EXTERNAL POWER Now we turn on the Main Battery Toggle Switch. AC BUS 2 AC BUS 1 STBY BUS INV 1 INV 2 EMER BUS ESS BUS OFF ON HOT EMER BAT BUS HOT MAIN BAT BUS OVRD BAT EMER BAT CHG MAIN BAT CHG 0 1 DC BUS 1 DC 2 DCH + - + Hot Emergency Battery 1 Hot Main Battery DC BUS 2 2 CH BAT SEL EMERG MAIN BTC SHED DC SVCE BUS SBTR EGHR DC SVCE/UTLY BUS SHED DC GEN 1 EXT PWR AVAIL DC GEN 2 - GND HDLG BUS BTR EXTERNAL POWER Now we turn on the Main Battery Toggle Switch. AC BUS 2 AC BUS 1 STBY BUS INV 1 INV 2 EMER BUS ESS BUS OFF ON HOT EMER BAT BUS HOT MAIN BAT BUS OVRD BAT EMER BAT CHG MAIN BAT CHG 0 1 DC BUS 1 DC 2 DCH + - + Hot Emergency Battery 1 Hot Main Battery DC BUS 2 2 CH BAT SEL EMERG MAIN BTC SHED DC SVCE BUS SBTR EGHR DC SVCE/UTLY BUS SHED DC GEN 1 EXT PWR AVAIL DC GEN 2 - GND HDLG BUS BTR EXTERNAL POWER Now we turn on the Main Battery Toggle Switch. AC BUS 2 AC BUS 1 STBY BUS INV 1 INV 2 EMER BUS ESS BUS OFF ON HOT EMER BAT BUS HOT MAIN BAT BUS OVRD BAT EMER BAT CHG MAIN BAT CHG 0 1 DC BUS 1 DC 2 DCH + - + Hot Emergency Battery 1 Hot Main Battery DC BUS 2 2 CH BAT SEL EMERG MAIN BTC SHED DC SVCE BUS SBTR EGHR DC SVCE/UTLY BUS SHED DC GEN 1 EXT PWR AVAIL DC GEN 2 - GND HDLG BUS BTR EXTERNAL POWER 115 VAC SBY 26 VAC SBY Now with the main battery on, these buses are powered. AC BUS 1 DC STBY BUS AC BUS 2 STBY BUS BUS OFF INV 1 INV 1 DC ESS BUS DC EMER BUS BUS INV OFF FAULT INV 2 EMER BUS SBTC ESS BUS HEBTC OFF ON HBTC HMBTC HOT EMER BAT BUS HOT MAIN BAT BUS OVRD BAT EMER BAT CHG MAIN BAT CHG 0 1 DC BUS 1 DC 2 DCH DC BUS OFF + - + Hot Emergency Battery 1 Hot Main Battery DC BUS 2 2 CH DC BUS OFF BAT SEL EMERG MAIN BTC SHED DC SVCE BUS SBTR EGHR DC SVCE/UTLY BUS SHED SBTC DC =GEN Standby Bus Transfer Contactor 1 EXT PWR DC GEN 2 HMBTC = Hot Main Bus Transfer Contactor FAULT AVAIL FAULT HEBTC = Hot Emergency Bus Transfer Contactor HBTC = Hot Battery Transfer Contactor - GND HDLG BUS BTR EXTERNAL POWER 115 VAC SBY 26 VAC SBY When the external power pushbutton is depressed, these buses are powered. AC BUS 1 DC STBY BUS AC BUS 2 STBY BUS BUS OFF INV 1 INV 1 DC ESS BUS DC EMER BUS BUS INV OFF FAULT INV 2 EMER BUS SBTC ESS BUS HEBTC OFF ON HBTC HMBTC HOT EMER BAT BUS HOT MAIN BAT BUS OVRD BAT EMER BAT CHG MAIN BAT CHG 0 1 DC BUS 1 DC 2 DCH DC BUS OFF + - + Hot Emergency Battery 1 Hot Main Battery DC BUS 2 2 CH DC BUS OFF BAT SEL EMERG MAIN BTC SHED DC SVCE BUS SBTR EGHR DC SVCE/UTLY BUS SHED DC GEN 1 EXT PWR DC GEN 2 FAULT AVAIL FAULT - GND HDLG BUS BTR EXTERNAL POWER 115 VAC SBY ASTR 26 VAC SBY When the external power pushbutton is depressed, these buses are powered. AC BUS 1 115 VAC BUS 1 115 VAC BUS 2 26 VAC BUS 1 26 VAC BUS 2 INV 1 DC STBY BUS INV 2 EMER BUS DC ESS BUS DC EMER BUS BUS INV OFF FAULT INV 1 INVERTER FAIL SIGNAL ACBTR AC BUS 2 STBY BUS BUS OFF #1 INVERTER FAIL SIGNAL SDTC SBTC ESS BUS HEBTC OFF ON HBTC HMBTC HOT EMER BAT BUS HOT MAIN BAT BUS OVRD BAT EMER BAT CHG MAIN BAT CHG 0 1 DC BUS 1 1 DC BUS 2 DC 2 DCH DC BUS OFF CH - DC BUS 1 2 DC BUS OFF BAT SEL EMERG + MAIN BTC SHED DC SVCE BUS + UTILITY UTILITY BUS 1 BUS 2 SBTR EGHR DC SVCE/UTLY BUS SHED DC GEN 1 EXT PWR DC GEN 2 FAULT AVAIL FAULT ON GND HDLG BUS BTR EXTERNAL POWER DC BUS 2 INV 2 115 VAC SBY ASTR 26 VAC SBY #1 INVERTER FAIL SIGNAL When DC Bus 1 is powered the Static Inverter Override Transfer Contactor (SDTC) closes and the HBTC (Hot INV 1 Bat Transfer Contactor opens). AC BUS 1 115 VAC BUS 1 115 VAC BUS 2 26 VAC BUS 1 26 VAC BUS 2 DC STBY BUS DC ESS BUS DC EMER BUS STBY BUS INV 2 EMER BUS INVERTER FAIL SIGNAL ACBTR AC BUS 2 INV 1 INV 2 SDTC SBTC ESS BUS HEBTC OFF ON HBTC HMBTC HOT EMER BAT BUS HOT MAIN BAT BUS OVRD BAT EMER BAT CHG MAIN BAT CHG 0 1 DC BUS 1 1 DC BUS 2 DC 2 DCH CH - DC BUS 1 2 BAT SEL EMERG + MAIN BTC SHED DC SVCE/UTLY BUS SHED DC GEN 1 EXT PWR DC GEN 2 FAULT AVAIL FAULT ON DC SVCE BUS + UTILITY UTILITY BUS 1 BUS 2 DC BUS 2 SBTR EGHR Once the DC Buses are powered, EXTERNAL POWER the associated lights are GND HDLG BUS extinguished on the main electrical BTR panel.
