GENERATOR DRIVE -BACKUP GENERATOR -HEAT EXCHANGER AND VALVE
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GENERATOR DRIVE -BACKUP GENERATOR -FUNCTIONAL DESCRIPTION
General
The backup generator converter sends data from backup generator components to the systems ARINC 629 buses. The EEC puts oil temperature and oil filter data on the systems ARINC 629 buses. This permits AIMS to show EICAS messages and maintenance data.
Charge Pressure Switch
If the backup generator has low oil pressure, the charge pressure switch closes. If the charge pressure switch closes while the related engine is running and the backup generator oil temperature is above 20C, the backup converter trips the generator field. This causes the BACKUP GEN OFF light to come on. Low oil pressure also causes the ELEC BACKUP GEN message.
Oil Level Sensing
The remote oil level sensors send an oil level signal to the backup generator converter. The sensors send data only when the oil pressure is low (generator is shutdown). The electrical maintenance page shows the oil level data of the backup generator. The oil level data shows two dashes when the backup generator operates.
If oil does not cover the underfill sensor, the backup generator oil level is too low. The maintenance page will show SERVICE when the backup generator is shutdown.
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If oil covers the underfill sensor, but not the overfill sensor, the backup generator has sufficient oil. The maintenance page will show NORMAL when the backup generator is shutdown.
If oil covers the two oil level sensors, the backup generator oil level is too high. The maintenance page will show SERVICE when the backup generator is shutdown.
The oil level data is blank for any of these conditions:
*
Engine shutdown (blank for approximately 10 minutes)
*
Initial converter power-up (blank for approximately 10 minutes)
*
Data is invalid due to a fault.
Oil Filter Status
The differential pressure switch monitors the difference between the pressures upstream and downstream of the oil filter. The switch sends a filter status signal through the EEC and the systems ARINC 629 buses to the backup generator converter. The backup generator converter causes the electrical maintenance page to show the status of the oil filter. The usual status on the maintenance page is NORMAL.
When the oil filter is clogged, the differential pressure switch closes. The backup generator converter causes the electrical maintenance page to change the filter status to BLOCKED. The backup generator converter inhibits the filter status signal when the oil out temperature is less than 145F (62C).
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GENERATOR DRIVE -BACKUP GENERATOR -FUNCTIONAL DESCRIPTION
Temperature Data
Oil temperature sensors in the inlet and outlet tubing send data to the EEC. The EEC sends the data to AIMS. The electrical maintenance page shows OUT TEMP, the temperature of the oil at the backup generator outlet. It also shows RISE TEMP, the difference between the inlet and the outlet temperatures.
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GENERATOR DRIVE -BACKUP GENERATOR -FUNCTIONAL DESCRIPTION
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D633W101-BEJ Sep 05/2003
777 AIRCRAFT MAINTENANCE MANUAL
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GENERATOR DRIVE -BACKUP GENERATOR -OIL SERVICING
Oil Level Indication
The signal from the remote oil level sensor causes the electrical maintenance page to show the backup generator oil level data. The maintenance page shows the oil level data as NORMAL or SERVICE.
The sightglass on the backup generator shows the oil level also. You must open the left thrust reverser cowl to see the sightglass.
The sightglass has two sets of oil level zones. You use one set when the generator is on the left engine. You use the other set when the generator is on the right engine.
The related center area of the sightglass is the normal zone. If the oil level is in the normal zone, the backup generator oil quantity is satisfactory. The related black zone at the top of the sightglass is the overfull zone. You must drain some oil from the generator if the level is in the overfull zone. The black zone at the bottom of the sightglass is the low oil zone. You must add oil to the generator if the oil level is in the low oil zone.
Add Oil to the Generator
You add oil to the generator through the backup generator pressure fill valve. It is above an access door in the thrust reverser at the 6:00 position.
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