The Electrical System

1. HOT EMER BAT BUS HOT MAIN BAT BUS Hot Emergency Battery Hot Main Battery + + - - GND HDLG BUS The Electrical System 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. Cargo Door Access Panel 2. Refueling Panel 3. Main Cabin Door 4. Auxiliary Hydraulic Pump Push Button is depressed. BTR

2. AC BUS 2 AC BUS 1 STBY BUS INV 1 INV 2 HOT EMER BAT BUS HOT MAIN BAT BUS EMER BUS ESS BUS OFF ON OVRD Hot Emergency Battery BAT Hot Main Battery EMER BAT MAIN BAT CHG CHG 0 1 1 DC BUS 1 DC BUS 2 DC 2 2 CH DCH BAT SEL + + - - EMERG MAIN BTC EXTERNAL POWER SHED DC SVCE/UTLY BUS GND HDLG BUS SHED DC GEN 1 EXT PWR DC GEN 2 BTR AVAIL If you walk into the cockpit and observe a GREEN AVAIL light on the main electrical panel, these buses are now powered. The Electrical System When the GPU is plugged in, the External Ground Handling Relay closes taking priority over the Bus Transfer Relay. The BTR then opens. EGHR

3. CALLS SMOKE GND SVCE BUS EMER PASS LAV CAPT LAV CARGO LT DC AC ON LAT UPR AFT READ PASS PASS CARGO LT GALLEY LAV DIM ENTR VENT HOT EMER BAT BUS HOT MAIN BAT BUS Hot Emergency Battery Hot Main Battery DC SVCE BUS + + - - EGHR EXTERNAL POWER GND HDLG BUS BTR 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. The Electrical System The GPU is now powering the Ground Handling Bus and the DC Service Bus. SBTR

4. AC BUS 2 AC BUS 1 STBY BUS HOT EMER BAT BUS HOT MAIN BAT BUS EMER BUS ESS BUS Hot Emergency Battery Hot Main Battery 0 1 1 DC BUS 1 DC BUS 2 DC 2 2 CH DCH DC SVCE BUS + + - - EGHR EXTERNAL POWER GND HDLG BUS SHED BTR Now we turn on the Main Battery Toggle Switch. The Electrical System INV 1 INV 2 OFF ON OVRD BAT EMER BAT MAIN BAT CHG CHG SBTR BAT SEL EMERG MAIN BTC SHED DC SVCE/UTLY BUS DC GEN 1 EXT PWR DC GEN 2 AVAIL

5. AC BUS 2 AC BUS 1 STBY BUS HOT EMER BAT BUS HOT MAIN BAT BUS EMER BUS ESS BUS Hot Emergency Battery Hot Main Battery 0 1 1 DC BUS 1 DC BUS 2 DC 2 2 CH DCH DC SVCE BUS + + - - EGHR EXTERNAL POWER GND HDLG BUS SHED BTR Now we turn on the Main Battery Toggle Switch. The Electrical System INV 1 INV 2 OFF ON OVRD BAT EMER BAT MAIN BAT CHG CHG SBTR BAT SEL EMERG MAIN BTC SHED DC SVCE/UTLY BUS DC GEN 1 EXT PWR DC GEN 2 AVAIL

6. AC BUS 2 AC BUS 1 STBY BUS HOT EMER BAT BUS HOT MAIN BAT BUS EMER BUS ESS BUS Hot Emergency Battery Hot Main Battery 0 1 1 DC BUS 1 DC BUS 2 DC 2 2 CH DCH DC SVCE BUS + + - - EGHR EXTERNAL POWER GND HDLG BUS SHED BTR Now we turn on the Main Battery Toggle Switch. The Electrical System INV 1 INV 2 OFF ON OVRD BAT EMER BAT MAIN BAT CHG CHG SBTR BAT SEL EMERG MAIN BTC SHED DC SVCE/UTLY BUS DC GEN 1 EXT PWR DC GEN 2 AVAIL

7. 26 VAC SBY 115 VAC SBY INV 1 DC STBY BUS DC ESS BUS DC EMER BUS AC BUS 2 AC BUS 1 HBTC STBY BUS SBTC BUS BUS INV OFF OFF FAULT HEBTC HMBTC HOT EMER BAT BUS HOT MAIN BAT BUS EMER BUS ESS BUS Hot Emergency Battery Hot Main Battery SBTC = Standby Bus Transfer Contactor HMBTC = Hot Main Bus Transfer Contactor 0 HEBTC = Hot Emergency Bus Transfer Contactor 1 1 HBTC = Hot Battery Transfer Contactor DC BUS 1 DC BUS 2 DC 2 2 CH DCH DC BUS DC BUS OFF OFF DC SVCE BUS + + - - EGHR EXTERNAL POWER GND HDLG BUS SHED BTR FAULT The Electrical System Now with the main battery on, these buses are powered. INV 1 INV 2 OFF ON OVRD BAT EMER BAT MAIN BAT CHG CHG SBTR BAT SEL EMERG MAIN BTC SHED DC SVCE/UTLY BUS DC GEN 1 EXT PWR DC GEN 2 AVAIL FAULT

8. 26 VAC SBY 115 VAC SBY INV 1 DC STBY BUS DC ESS BUS DC EMER BUS AC BUS 2 AC BUS 1 HBTC STBY BUS SBTC BUS BUS INV OFF OFF FAULT HEBTC HMBTC HOT EMER BAT BUS HOT MAIN BAT BUS EMER BUS ESS BUS Hot Emergency Battery Hot Main Battery 0 1 1 DC BUS 1 DC BUS 2 DC 2 2 CH DCH DC BUS DC BUS OFF OFF DC SVCE BUS + + - - EGHR EXTERNAL POWER GND HDLG BUS SHED BTR FAULT The Electrical System When the external power pushbutton is depressed, these buses are powered. INV 1 INV 2 OFF ON OVRD BAT EMER BAT MAIN BAT CHG CHG SBTR BAT SEL EMERG MAIN BTC SHED DC SVCE/UTLY BUS DC GEN 1 EXT PWR DC GEN 2 AVAIL FAULT

9. #1 INVERTER FAIL SIGNAL 26 VAC SBY 115 VAC SBY 115 VAC BUS 1 115 VAC BUS 2 INV 1 INV 2 26 VAC BUS 1 26 VAC BUS 2 INVERTER FAIL SIGNAL DC STBY BUS DC ESS BUS DC EMER BUS AC BUS 2 AC BUS 1 HBTC STBY BUS BUS BUS INV OFF OFF FAULT HEBTC HMBTC SDTC HOT EMER BAT BUS HOT MAIN BAT BUS EMER BUS ESS BUS DC BUS 1 DC BUS 2 UTILITY BUS 1 UTILITY BUS 2 0 1 1 DC BUS 1 DC BUS 2 DC 2 2 CH DCH DC BUS DC BUS OFF OFF DC SVCE BUS + + - - EXTERNAL POWER GND HDLG BUS SHED FAULT The Electrical System ASTR When the external power pushbutton is depressed, these buses are powered. ACBTR SBTC INV 1 INV 2 OFF ON OVRD BAT EMER BAT MAIN BAT CHG CHG SBTR BAT SEL EMERG MAIN BTC EGHR SHED DC SVCE/UTLY BUS DC GEN 1 EXT PWR DC GEN 2 BTR AVAIL FAULT ON

10. #1 INVERTER FAIL SIGNAL 26 VAC SBY 115 VAC SBY 115 VAC BUS 1 115 VAC BUS 2 INV 1 INV 2 26 VAC BUS 2 26 VAC BUS 1 INVERTER FAIL SIGNAL DC STBY BUS DC ESS BUS DC EMER BUS AC BUS 2 AC BUS 1 STBY BUS HBTC HEBTC HMBTC SDTC HOT EMER BAT BUS HOT MAIN BAT BUS EMER BUS ESS BUS DC BUS 1 DC BUS 2 UTILITY BUS 1 UTILITY BUS 2 0 1 1 Once the DC Buses are powered, the associated lights are extinguished on the main electrical panel. DC BUS 1 DC BUS 2 DC 2 2 CH DCH DC SVCE BUS + + - - EXTERNAL POWER GND HDLG BUS SHED FAULT The Electrical System ASTR When DC Bus 1 is powered the Static Inverter Override Transfer Contactor (SDTC) closes and the HBTC (Hot Bat Transfer Contactor opens). ACBTR SBTC INV 1 INV 2 OFF ON OVRD BAT EMER BAT MAIN BAT CHG CHG SBTR BAT SEL EMERG MAIN BTC EGHR SHED DC SVCE/UTLY BUS DC GEN 1 EXT PWR DC GEN 2 BTR AVAIL FAULT ON

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