TM 55-1520-240-23-7
9-30
ALTERNATING CURRENT (AC) POWER DISTRIBUTION
(Continued)
9-30
EXTERNAL POWER OPERATION
When an external power source is connected to the
helicopter, the ground power monitor in the left electrical
compartment checks that the source meets the proper
input requirements. If it does, the monitor supplies 28
vdc to energize external power contactor 241K5. This
allows 28 vdc from the essential bus to energize APU
generator contactor 241K3, putting voltage from the
external power source at the No. 1 and No. 2 buses.
NO BREAK - WORK HARDER
When power is being supplied by external power,
contactor 241K5 provides a ground to light the EXT
PWR light on the master caution panel.
NO BREAK - WORK HARDER
External power cannot be applied if the APU or main
generators are operating.
END OF TASK
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