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attempt to reset the breaker more
than one time. Repeated tripping of a
circuit breaker is an indication of a
possible problem with equipment or
electrical wiring. Multiple attempts
to reset the circuit breaker may result
in equipment damage and/or an
electrical fire.
2.47.1 DC Power Supply System. Two essential ac
busses supply power to the two 350-ampere T/Rs
through the XFMR RECT 1 and XFMR RECT 2 circuit
breakers on the pilot overhead circuit breaker panel
(fig 2-39). The No.1 and No. 2 T/Rs convert the ac input
to 28 vdc. The 28 vdc power is applied to a dc
contactor, which routes 28 vdc from T/R No. 1 to the No.
1 essential dc bus and from T/R No.2 to the No. 2 essential
dc bus. The No. 1 and No. 2 essential dc buses each
apply 28 vdc, in parallel, through isolation diodes to
power the emergency dc bus during normal operation.
For emergency operation, the battery powers the emergency
dc bus, and the emergency dc bus diodes isolate
the battery from the noncritical loads. The two essential
dc buses also supply 28 vdc power to the No. 3 essential
dc bus. The T/Rs are self-monitoring for overtemperature
and will illuminate the HOT RECT 1 and
HOT RECT 2 caution lights on the pilot caution/warning
panel when an overheat condition exists. The dc
contact or monitors the T/Rs for output loss or drop in
voltage. If the dc contactor senses a fault in T/R No. 1,
it disconnects T/R No. 1 from the No. 1 essential dc bus
and illuminates the RECT 1 caution light on the pilot
caution/warning panel. At the same time, it connects
No. 1 essential dc bus to No. 2 essential dc bus through
relay action inside the contactor. The same action takes
place if T/R No. 2 fails. If both T/Rs fail, the ELEC SYS
FAIL caution light on the CPG caution/warning panel
will illuminate. The caution/warning lights receive 28
vdc from the emergency dc bus through the CAUT circuit
breaker on the pilot overhead circuit breaker panel
and the EMERG BATT CAUT circuit breaker on the
CPG main circuit breaker panel (fig 2-40).
a. Battery. A 24-volt, 13 ampere-hour, 19 cell,
nickel-cadmium battery provides emergency power.
The battery is located in the aft avionics bay. The battery
is charged by the battery charger which receives
28 vdc power from the No. 1 essential dc bus through
the BATT CHGR DC circuit breaker and 115 vac from
the No. 2 essential ac bus through the BATT CHGR
AC circuit breaker. Both circuit breakers are on the pilot
overhead circuit breaker panel. The battery charger
will completely charge the battery and then maintain a
trickle charge. The battery charger also contains fault
sensing that monitors battery temperature, cell balance,
and charger operation. If a fault occurs, either the
HOT BAT or CHARGER caution light will illuminate
on the pilot caution/warning panel. The helicopter is
equipped with a battery heater which operates automatically
when the battery is on.
b. CPG Battery Override Switch. A two-position
guarded toggle BAT OVRD switch is located on the
CPG PWR lever quadrant (fig 2-12). With the guard
down, the switch is in the NRML position and enables
the pilot EXT PWR/BATT switch on the pilot ELEC
PWR control panel (fig 2-37) located on the left console
(fig 2-11). When the guard is positioned up and the
switch is set to OVRD, the pilot EXT PWR/BATT
switch is inoperative, and the battery is disconnected
from the emergency dc bus.
2.47.2 AC Power Supply System. The ac power sup
ply system is the primary source of electrical power. It
supplies 115 vac from twO 35 kilovolt-ampere generators.
Each generator and its associated components
comprise an independent ac generating system that
supplies about one-half of the total electrical requirements
to the ac buses. The generators are mounted on,
and driven by, the main transmission accessory gear
box. The 115 vac power is monitored and regulated by
the generator control unit (GCU). If the generator output
is normal, the GCU applies voltage to the ac contactor
which energizes and connects the generator output
2-66 Change 2
TM 1-1520-238-10
to the ac essential buses. The No. 1 ac contactor
connects the No. 1 generator output to the No. 1
essential ac bus, and the No. 2 ac contactor connects
the No. 2 generator to the No. 2 essential ac bus. If
one generator fails, its load is automatically connected to
the remaining generator.
a. Generators. Two generators, located on the
main transmission accessory gearbox, supply 115 vac,
three-phase power for operating the helicopter electrical
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阿帕奇攻击直升机操作手册1(44)
