*
Fire switch pulled
*
Over/under voltage
*
Over/under frequency
*
Differential fault
*
Open phase
*
Generator diode failure
*
Parallel feeder open
*
Unbalanced current
*
Computer failure.
A protective trip is reset when you push the control switch off and then on.
Power Feeders
Copper feeders go from the APU to a terminal block at the aft stabilizer pivot bulkhead. From there, double-wire aluminum feeders go to the auxiliary power panel. The feeders reconnect in the power panel.
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AC GENERATION -APU GENERATOR POWER -GENERATOR CONTROL
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AC GENERATION -APU GENERATOR POWER -APB CONTROL
APB Control
The APU GCU controls the automatic operation of the APB. The GCU gets a switch position signal from the APU generator (APU GEN) switch.
When the switch is in, the GCU operates the APB automatically. The GCU uses power transfer logic to make a decision when to close the APB. In the air, with a single IDG operating, the APB closes if the APU is running (a break-power transfer). On the ground, the APB closes for no-break power transfers.
The GCU opens the APB for any these conditions:
*
The APU is off
*
Secondary external power is on
*
An APU power system fault occurs.
When the switch is out, a direct wire to the APB supplies power to open the breaker.
Switch Light
The OFF light on the APU GEN switch comes on for any of these conditions:
*
The switch is out and the APB is open
*
The APU is running and the GCU opens the APB because of a fault.
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AC GENERATION -APU GENERATOR POWER -APB CONTROL
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AC GENERATION -IDG POWER -GENERATOR CONTROL
General
The IDG GCU controls, protects, and monitors the IDG power.
The forward equipment cooling system actively cools the GCU.
GCU Power
The GCU gets power for control, protection, and BITE functions from these sources:
*
IDG PMG
*
Battery bus #2
*
Right dc bus.
Generator Excitation
The voltage regulator controls the power level to the exciter field in the IDG. The voltage regulator rectifies ac power from the PMG to make dc current for the exciter field. Power to the voltage regulator goes through the generator control relay (GCR).
The generator uses the exciter field current to make the ac current in the power feeders. The power feeders go to the GCB in the power panel.
Point-of-Regulation (POR) Voltage
The voltage regulator monitors the voltage at the POR. POR is on the generator side of the GCB. The voltage regulator adjusts the dc current to the exciter field to keep the POR voltage at 115 volts.
Protection
The GCU monitors the IDG generator power and control inputs. It opens the GCR for any of these causes:
*
Control switch off
*
Fire switch pulled
*
IDG disconnect switch pushed
*
Over/under voltage
*
Over/under frequency
*
Differential fault
*
Open phase
*
Generator diode failure
*
Parallel feeder open
*
Unbalanced current
*
Computer failure.
A protective trip is reset when you push the control switch off and then on.
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AC GENERATION -IDG POWER -GENERATOR CONTROL
Power Feeders
Copper feeders go from the IDG to a terminal block under the strut. From there, double-wire copper feeders go through the strut to a splice in the wing leading edge. At the splice, the feeders change from copper to aluminum. Another splice is at the wing-to-body join. The feeders reconnect in the power panel.
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AC GENERATION -IDG POWER -GENERATOR CONTROL 中国航空网 www.aero.cn 航空翻译 www.aviation.cn 本文链接地址：777 AMM 飞机维护手册 电源 Electrical Power(24)
