747-400 AMM 飞机维护手册 ELECTRICAL POWER 电源 2(5)

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UNDERVOLTAGE (UV)  3-PHASE POR AVERAGE OF VOLTAGES  <104.5 |1.5 VOLTS  9.75 +0.25 SEC  GCR, GCB  LOCKED OUT BY UNDERSPEED 
(OF1) OVERFREQUENCY (OF2)  PMG EFFECTIVE FREQUENCY FO IDG FREQUENCY  GENERATOR 427.5 |2.5 Hz 437.5 |2.5 Hz MINIMUM GENERATOR FREQUENCY FREQUENCY  MSEC MSEC (CONCUR-RENT) 1.2 |0.4 SEC (CON-CURRENT) 30 |10 475 |25  BTB GCR, GCB GCR, GCB  THRESHOLD FREQUENCY IS PMG FREQUENCY DIVIDED BY THREE 
UNDERFREQUENCY (UF1) (UF2)  FREQUENCY FO EFFECTIVE IDG FREQUENCY  372.5 |2.5 Hz GENERATOR FREQUENCY GENERATOR 352.5 |2.5 Hz FREQUENCY  475 |25 MSEC MSEC (CONCUR-RENT) 1.2 |0.4 SEC (CON-CURRENT) 150 |50  BTB GCR, GCB GCR, GCB  LOCKED OUT BY UNDERSPEED; FREQUENCY DIVIDED BY THREE THRESHOLD FREQUENCY IS PMG
UNDERSPEED  IDG INPUT  4,450 |50 RPM  150 |50  GCB  LOCKS OUT UNDERFREQUENCY AND 
(US)  SPEED (MPU)  RPM (UPPER LIMIT) (LOWER LIMIT) TO 4,650 |50  MSEC MAXIMUM  UNDERVOLTAGE 
DIFFERENCE CURRENT PROTECTION (DCP)  AVERAGE OF GENERATOR GENERATORS PARALLELED OUTPUT VS.  DIFFERENCE OF í37.50 |2.50 AMPS  INVERSE  BTB 
(DP) CURRENT PROTECTION DIFFERENTIAL  GENERATOR LINE DPCT DPCT AND  ABSOLUTE CURRENT AND SUM OF LOAD AND SYNC BUS CURRENT BETWEEN GENERATOR DIFFERENCE 20 |5 AMPS  (DP1) |22.5 MSEC (DP2) 52.5 MAXIMUM 40 MSEC  GCR, GCB BTB 

Generator Control Unit (GCU) Protective Functions
Figure 4 (Sheet 1)

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MAINTENANCE MANUAL

FUNCTION  SENSING  THRESHOLD  DELAY TIME  TRIPS  REMARKS 
GENERATOR  ACTUAL MEASURED  ACTUAL VOLTAGE >  6.25  GCR, GCB 
DIODE FAULT  CALCULATED GENERATOR VOLTAGE EXCITER FIELD VOLTAGE VS.  CALCULATED GENERATOR VOLTAGE  |0.75 SEC 
(OE) OVEREXCITATION  OE/UE CT 3-PHASE VOLTAGE AT POR AND  130 |3 VOLTS AC  INVERSE  BTB, GCR 
UNDEREXCITA-TION (UE)  OE/UE CT 3-PHASE VOLTAGE AT POR AND  AC 104.5 |1.5 VOLTS  3.00 |0.25 SEC  BTB, GCR 
SHORTED PMG (SPMG)  PMG RIPPLE VOLTAGE  PMG RIPPLE DETECTOR  SEC 0.7 |0.5  GCR, GCB 
OPEN PHASE  LINE DPCT  LOWEST PHASE, <  375 |40  BTB 
(OP)  CURRENT  55 |5 AMPS 2 PHASES, í 6 |5 AMPS, OTHER  (CONCUR-RENT) (OP2) (CONCUR-RENT) 9 |1 SEC (OP1) MSEC  GCR, GCB 
REVERSE POWER  CTA OUTPUT  8 |1 kW  INVERSE  BTB  CONDITION ONLY OPERATES IN UNDERSPEED
CPU FAULT (FAILSAFE)  WATCHDOG  IMMEDIATE  GCR, GCB  FAULT BTB TRIPS FOR A MAIN BUS 
POWER READY  NONE  OV, UV, OF1, UF1, US  150 |50 MSEC  GCB WILL CLOSE IF NO TRIPS ARE PRESENT 

Generator Control Unit (GCU) Protective Functions
Figure 4 (Sheet 2)

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747-400 MAINTENANCE MANUAL
 3) Overfrequency 4) Underfrequency 5) Underspeed 6) Difference current 7) Differential current 8) Open phase 9) Generator diode fault 10) Overexcitation 11) Underexcitation 12) Reverse power 13) Central processing unit fault 14) Shorted permanent magnet generator 15) Pole slip 16) Disconnect and fire switch shutdownThe GCU provides the following control functions: 1) Generator field control and indication 2) Generator circuit breaker control and indication 3) Bus tie breaker control and indication 4) Automatic bus isolation control (autoland) 5) DC isolation relay control 6) IDG air/oil cooling valve control 7) Utility load management control functions (sent via ARINC
 429 to BCU for control) 8) Bus off indication (dead bus through ARINC 429 data link)During fault conditions, the excitation level to the generator is automatically controlled to limit current and/or power output of the associated generator to within safe levels.The GCU also controls various breakers and relays; they are closed when no fault conditions exist and they can be opened automatically when required. The GCU controls the GCR (a relay in the GCU which opens and closes the generator field circuit), the GCB (a breaker which connects the generator to its associated load bus), and the BTB (a latching-type relay which connects the main generator buses to the sync bus).The voltage regulation portion of the GCU maintains the generator voltage at the point of regulation. The regulator senses the voltage at the point of regulation and compares this against a reference voltage. If a difference exists, it will adjust the generator exciter field current to maintain a constant voltage at the point of regulation.
　
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