FUNCTION FAULT DIFFERENTIAL SYNC BUS SENSING 3 PHASE SYNC BUS DPCT THRESHOLD 30 |5 AMPS DELAY TIME MSEC 155 |5 TRIPS XPC, APB, BTBs ADJACENT SSB, REMARKS
SYNC BUS REDUNDANT FAULT DIFFERENTIAL 3 PHASE SYNC BUS DPCT 30 |5 AMPS MSEC 130 |10 BTBs ADJACENT SSB, HAS FAILED ACTIVE ONLY WHEN THE CPU
INTLK EXT PWR PIN "F" PIN "E" CONTACTS INTERNAL XPC
UNLIKE SOURCE (SUSP) PARALLEL SUSTAINED SSB BTBs GCBs APBs XPCs POSITION OF: SOURCES BETWEEN UNLIKE PARALLELING MSEC 135 |15 ARE POWERS AUX IDG'S OR ARE BTB - IF POWER IN-VOLVED) INVOLVED (NO IDG APB - IF EXT AND INVOLVED XPC AND2. ADJACENT1. RECLOSED SOURCE MUST BE MANUALLY ARE TRIPPED, THE SELECTED AFTER BOTH THE XPC AND APB
CPU FAILURE FAILURE WATCHDOG TIMERS SUPPLIES CPU POWER SOFTWARE ERRORS FAILURES SUPPLIES ON CPU POWER XPC, APB, GSSR, GSTR, GHRs
Bus Control Unit (BCU) Protective Functions
Figure 6 (Sheet 2)
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b) APU Power Ready signal is present. c) Actuation of the APU GEN switch has been sensed.
2) The BCU will send a remote APB close signal to the AGCU when the airplane is in ground mode and the following conditions are all true: a) APB is open. b) APU Power Ready signal is present. c) Actuation of the APU GEN switch has been sensed. d) Auto Parallel Ready signal is present.
3) The BCU will send a remote APB trip signal to the AGCU and an APB trip command to the APB when any of the following are true: a) AGCR is commanded to trip by the BCU. b) APB SUSP command is present. c) Synchronizing bus fault protection signal is present. d) Transfer from auxiliary power to IDG power is complete. e) Transfer from auxiliary power to external power is
complete. f) Actuation of the APU GEN switch when the APB is closed.
(d) The BCU provides the interface between the EXT PWR switch and the XPC. The BCU can also trip the XPC as part of the control and protection function. 1) The BCU will send a continuous XPC close command to the XPC
if the following conditions are all true:
a) Actuation of the EXT PWR switch has been sensed.
b) Airplane is in ground mode.
c) External power AVAIL signal is present.
d) XPC is open.
2) The BCU will remove the XPC close command to the XPC if any of the following conditions are true: a) External power plug is disconnected. b) External power protective trip occurs. c) Actuation of the EXT PWR switch has been sensed and the
XPC is closed.
d) Transfer to IDG power is complete.
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e) Transfer to auxiliary power is complete.
f) XPC SUSP command is present.
g) Synchronizing bus fault protection signal is present.
(e) The BCU provides the interface between the ground service switch and the GSSR and GSTR. When external power or auxiliary power are not available, the GSSR will not be energized (Ref 24-50-00). 1) The BCU will command the GSSR and GSTR to close and supply
the ground service bus with external power when the
following conditions are all true:
a) Ground service switch is actuated.
b) Airplane is in ground mode.
c) AC Bus 1 is not powered.
d) External power is available.
2) The BCU will command the GSTR to close and supply the ground service bus with auxiliary power when the following conditions are all true: a) Ground service switch is actuated. b) Airplane is in ground mode. c) AC Bus 1 is not powered. d) External power is not available. e) APU power ready signal is available.
3) The BCU will remove the GSTR and GSSR close command and supply the ground service bus with AC Bus 1 power when one of the following conditions are true: a) AC Bus 1 becomes powered. b) Ground service switch is actuated. c) External power plug is disconnected. d) XPC trip is present.
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