TM 1-1520-238-T-6
9–79
9–7.
SYSTEM DESCRIPTION (cont)
9–7
(c) The external power monitor checks the input power from the auxilliary ground power unit (AGPU). If
the power checks good, the external power contactor connects external power to the ac bus 1. The EXT PWR
indicator on the pilot’s caution/warning panel lights whenever the access door to the external power receptacle is
opened.
(d) Power from ac bus 2 is directed to the ground service utility receptacle. The circuit is protected by
AC ELEC UTIL PWR circuit breaker (CB6).
M69-411
AC
GENERATOR
GCU 1
AC
GENERATOR
GCU 2
GEN 1 AC
CONTACTOR
AC ESS BUS 1
AC ESS BUS 2
EXTERNAL
POWER
CONTACTOR
T / R 1
DC TIE BUS CONTACTOR
T / R 2
EXTERNAL
POWER
MONITOR
DC ESS
BUS 1
DC ESS
BUS 2
DC EMERG BUS
BATTERY CHARGER
BATTERY
BATTERY RELAY
DC ESS
BUS 3
EXTERNAL
POWER
RECEPTACLE
PILOT ELEC
PWR PANEL
115 / 200 VAC
3Ø
400 Hz
115 / 200 VAC
3Ø
400 Hz
115 / 200 VAC
3Ø TO
28 VDC
GEN 2 AC
CONTACTOR
Figure 9–71.
Electrical System Functional Block Diagram
