When you supply power to the secondary receptacle, the two lights above the receptacle come on if the power quality is good and one of these conditions are true:
*
Primary receptacle has power
*
Battery switch is on.
Operate Control Switches
Push the ground service switch to apply power to the ground service bus. The light in the switch comes on when the ground service bus has power. The NOT IN USE light above the primary receptacle goes off when the ground service bus gets power.
The AVAIL light in the primary external power switch comes on if the power quality is good.
The AVAIL light in the secondary external power switch comes on if the power quality is good and one of these conditions are true:
*
Primary receptacle has power
*
Battery switch is on.
Push the battery switch on. Push the primary external power switch to apply primary ground power to the airplane electrical system. Push the secondary external power switch to apply secondary ground power to the airplane electrical system. When you supply power, the AVAIL lights go off and the ON lights come on.
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EXTERNAL POWER -OPERATION
Push the battery switch to off if the airplane is to have power with no personnel on board. This prevents the automatic operation of the standby power system if you lose all ground power.
Training Information Point
Use external power sources that have a power capacity of 90 kva or more for each power receptacle. If you do not, ELMS can remove all the loads it controls or the BPCU can open the external power contactor(s). See the Electrical Load Management System section for more information on load shedding (SECTION 24-09).
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BOEING PROPRIETARY -Copyright # -Unpublished Work -See title page for details.
AC DISTRIBUTION -INTRODUCTION
General
The distribution section of electrical power includes both ac and dc power distribution.
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AC DISTRIBUTION -GENERAL DESCRIPTION
General
The ac distribution system divides the electrical power ac buses into sections. This permits better control over small groups of electrical loads. It also protects against a severe loss of power due to a single electrical power failure.
These are the only components in the ac distribution system:
*
Electrical load control units (ELCU)
*
28v ac transformers.
A primary function of the ac distribution system is autoland bus isolation.
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AC DISTRIBUTION -ELECTRICAL LOAD CONTROL UNIT
General
The ELCUs control and protect the electrical power supplied to large ac loads. There are several ELCUs in the P100 and P200 power panels.
Physical Description
The ELCUs are LRMs of the ELMS power panels. The ELCUs contain these parts:
*
Current transformers
*
Contactor
*
Power supply
*
Control logic.
The ELCUs are ESDS components because of the wiring connections to the control logic.
Control
The ELCUs use these things to control their contactors:
*
Current transformers
*
Rating jumper
*
Input command.
The ELCU current transformers supply signals to the control logic for overcurrent and differential fault protection. The load current transformer signal supplies the second current signal necessary for differential fault protection. The control logic does not use the differential fault protection function if there is no load current transformer connected to the ELCU.
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