MD-11 Flight Crew Operations Manual
k
Electrical -
Description and Operation
Elec.10.5
• Emergency power transfer.
• Smoke procedure.
Protection for ac bus, galley bus, and equipment feeder faults is provided by
individual Remote Control Circuit Breakers (RCCB), Circuit Breakers (CB), or
fuses.
If galleys are installed, feeder fault and overload protection for the galley buses is
also provided by the Galley Load Control Units (GLCU).
DC Power
Transformer Rectifier (TR) Units
Four 75-amp TRs provide dc power to the aircraft dc buses (includes the battery
bus). The TRs convert 115-volt ac power into 28-volt dc power. The battery
and/or the ADG (through TR 3) may be used as emergency dc power sources.
DC Distribution
Four dc tie RCCBs are normally closed for parallel dc operation. This ensures all
dc loads are supplied power during start up, normal operation, shutdown, and
abnormal conditions.
An RCCB is used to connect each of the TRs to a common tie bus. This dc bus
arrangement allows supplying any single load from any one of the TRs.
If isolated, the four TRs receive ac power from the following ac buses:
• TR 1 receives power from ac generator bus 1.
• TR 2A receives power from ac generator bus 2.
• TR 2B receives power from the flight compartment ac ground service bus.
• TR 3 receives power from the right emergency ac bus.
Emergency Power
The emergency power system consists of one main battery, a battery charger, a
manually deployed ADG, and a static inverter.
The main battery is a 28-volt dc battery consisting of two 14-volt dc halves.
The battery charger converts ac input into a controlled dc output to keep the
battery fully charged. Battery power is supplied directly to the battery direct bus.
The battery can provide power to the left emergency ac and dc buses whenever the
left emergency ac or dc bus loses power. The battery direct bus is powered at all
times.
A static inverter inverts battery dc power into ac emergency power for the left
emergency ac bus.
October 02, 2006
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