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ELMS -FUNCTIONAL DESCRIPTION -EEU
Filters
There are three filter cards in each EEU, filter A (2) and filter C. P310 has an additional fourth card, filter B. The filter cards remove noise from the signals to and from the EEU circuit cards. The filter cards do not have a colored removal handle.
The filter A and filter C cards remove noise from the signals to and from the I/O cards. The filter B card removes noise from the signals to and from the dc subsystem and special function cards.
Training Information Point
The EEU and its circuit cards are ESDS components. You must use a wrist strap when you remove an EEU or any of its circuit cards.
I/O cards 7, 8, and 9 are not in P110 and P210. I/O card 7 is not in P310. System configuration on the MAT will show blanks for these cards.
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777 AIRCRAFT MAINTENANCE MANUAL
ELMS -FUNCTIONAL DESCRIPTION -EEU
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ELMS -FUNCTIONAL DESCRIPTION -EEU POWER
General
The ELMS power management panels operate with 28v dc power. Each power management panel has two power supply units (PSU) to control the power. The PSUs are circuit cards in the EEU. Two different dc power sources supply power to each PSU.
P110
The left power management panel gets power from the left and right dc buses.
P210
The right power management panel gets power from the left and right dc buses.
P310
The standby power management panel gets power from the battery #2 bus and the hot battery bus. The hot battery bus can supply power to P310 when any of these conditions occur:
*
Battery switch is on
*
Airplane is in the air
*
RAT is deployed
*
Refuel panel door is open.
The hot battery bus supplies control power to all of the relays that connect hot battery bus power to the P310 EEU.
Start Power Control
When the airplane has no power and you push the battery switch on, the ELMS start power control relay energizes. This supplies power to the P310 EEU so that it can energize the ground power battery relay. The ground power battery relay connects the hot battery bus to the battery No. 2 bus.
Hot Battery Latch
When the airplane is in the air or the RAT deploys, the hot battery latch relay energizes. This makes sure that the P310 EEU has power to control standby power operations even if the battery switch receives damage.
Refuel Power Control
When the integrated refuel panel door is open, the refuel power control relay energizes. This supplies power to the P310 EEU so that it can control the refuel valves.
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ELMS -FUNCTIONAL DESCRIPTION -EEU POWER
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ELMS -FUNCTIONAL DESCRIPTION -CONTROL
General
In addition to the distribution of electrical power, the ELMS also controls the switching of many electrical loads.
Control
Switching devices control the flow of electrical power to electrical loads. The ELMS controls these devices in one of these three ways:
*
EEU control
*
External control
*
Remote control.
For EEU control, the EEUs receive control signal inputs. EEU software decides when the switching device should operate. The EEUs then directly control the power switching device.
Other systems, external to the ELMS, also control switching devices in the ELMS panels. In these cases the ELMS has no control over the switching device.
For remote control, the EEUs control switching devices that are not in the power management panels. The EEUs supply a control signal that is either a ground for a remote relay or a logic discrete for a control unit.
Software
The EEU control software for a switching device can be simple or complex. For some devices, the software just repeats a command input with no processing. For other devices, the software requires many inputs and does much processing.
The software of the EEUs is data loadable.
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