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AC GENERATION -IDG POWER -BREAKER CONTROL
General
The GCU controls the GCB and BTB. When the GCB closes, the IDG connects to the main ac bus. When the BTB closes, the tie bus connects to the main ac bus.
The GCU gets switch position signals from the generator control (GEN CTRL) and BUS TIE switches.
GCB Control
When the GEN CTRL switch is in, the GCU operates the GCB automatically. The GCU closes the GCB when the IDG is available. This permits the left main ac bus to get power from the IDG. The GCU opens the GCB for any of these conditions:
*
Secondary external power is on
*
A fault occurs
*
The IDG is not available.
When the GEN CTRL switch is out, a direct wire to the GCB open coil supplies power to open the GCB.
The OFF light on the GEN CTRL switch comes on when the GCB is open.
BTB Control
When the BUS TIE switch is in, the GCU operates the BTB automatically. The GCU closes the BTB to permit either of these conditions:
*
The main ac bus gets power from the tie bus
*
The main ac bus supplies power to the tie bus.
The GCU opens the BTB for either one of these conditions:
*
The left GCB closes
*
A fault occurs.
When the BUS TIE switch is out, a direct wire to the BTB open coil supplies power to open the BTB.
The ISLN light on the BUS TIE switch comes on for either of these conditions:
*
The switch is out and the BTB is open
*
The GCU opens the BTB because of a fault.
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AC GENERATION -IDG POWER -BREAKER CONTROL
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AC GENERATION -BACKUP POWER -GENERATOR CONTROL
Converter Power
The converter power supply gets power from a PMG in the backup generator or from the captain’s flight instrument bus.
Generator Excitation
The voltage regulator controls power to the exciter field in the backup generator. The voltage regulator rectifies ac power from the PMG to make dc power for the exciter field. It sends power through the GCR to the exciter field. The generator uses the exciter field current to make variable frequency ac power. The generator sends variable frequency ac power to the converter.
Main Feeder Power
The rectifier changes the variable frequency ac power to dc power. The inverter changes dc power to constant frequency 115v ac power. The inverter sends the 115v ac power through the power feeders to the CCB.
The controller monitors the POR voltage. The POR is on the generator side of the CCB. The controller adjusts the output from the inverter to keep the POR voltage at 115v.
Protection
The backup generator converter monitors the backup generator power and control inputs. It opens the GCR for the related backup generator for any of these causes:
*
Control switch off
*
Fire switch pulled
*
Over/under-voltage
*
Over/under-frequency
*
Differential fault
*
Computer failure
*
Converter fault
*
Generator over-temperature
*
Low oil pressure
*
DC link over-voltage
*
Converter harmonic output distortion
*
DC content out of range
*
Converter over-current.
Under certain conditions the converter over-current fault does not trip the GCR.
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AC GENERATION -BACKUP POWER -GENERATOR CONTROL
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D633W101-BEJ Sep 05/2002
AC GENERATION -BACKUP POWER -BREAKER CONTROL
TBB and CCB Control
The backup generator converter controls the automatic operation of the TBB and CCB. The converter gets a switch position signal from the backup generator (BACKUP GEN) switch.
When the switch is in, the converter controls the TBB and CCB. The TBB and CCB are normally not energized. A spring holds the TBB closed when it is not energized. A spring holds the CCB open when it is not energized.
The converter energizes the TBB and CCB to permit the backup system to supply power to the transfer buses. The TBB opens when it energizes. The CCB closes when it energizes.
When the switch is out, the TBB and CCB are relaxed.
Power Transfer
The left transfer bus normally gets power from the left IDG, through the left GCB and left TBB. When the converter senses no power at the left main ac bus, it opens the left TBB and closes the left CCB. This permits power to go from the converter to the left transfer bus.
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