TM 55-1520-240-23-7
9-1
DIRECT CURRENT (DC) POWER DISTRIBUTION SYSTEM (Continued)
9-1
EXTERNAL POWER
When external dc power is applied to the helicopter, dc
external power control relay 161K9 is energized. This
disconnects the No. 1 and No. 2 transformer-rectifiers
from their respective buses by de-energizing their
respective RCCO relays. The energized power control
relay also lights the EXT PWR light on the master
caution panel.
At the same time, dc external power relay 161K7 is
energized to connect 24 vdc from the external source to
the No. 1 dc bus. This energizes relay 161K2, applying
power to the essential dc bus, bus tie relay 161K8,
powering the No. 2 bus, and energizes relay 161K10,
applying power to the switched battery bus.
9-16
Change 1
