(5)  
The ac standby bus is supplied by the left ac transfer bus. The battery bus, and dc standby, is supplied from the hot battery bus.

 (6)  
The hydraulic generator dc output normally exceeds battery terminal voltage, so the battery will not discharge. The battery will be available for transient demands encountered during approach and landing.

 (7)  
If normal power is recovered during flight both main ac buses are energized. After a 0.5 second time delay, the hydraulic shutoff valve closes and the generator shuts down. The bus transfer relays de-energize and the system returns to normal.

 (8)  
If an undervoltage or underfrequency occurs during hydraulic generator operation, the bus transfer relays will trip but the generator will remain excited. On the 5 kva HMG GCU, after 1.5 seconds a reset signal is automatically applied to the system. If the fault has not cleared, the reset circuit will continue to cycle. If the fault has cleared, the bus transfer relays will energize and supply the loads. If a trip occurs a second time within 30 seconds, the generator will continue to recycle until the fault is cleared.

 (9)  
AIRPLANES WITH 10 KVA HYDRAULIC MOTOR GENERATOR;

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MAINTENANCE MANUAL

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MAINTENANCE MANUAL

HYD RETURNHYD PRESSURER CASE DRAIN
ON
ELECT CONNECTORMOTOR SERVO
SERVO VALVEOVER-SPEED
CONT GEN
ELECT CONNECTOR
28V DC
1
CONT ACV3O 3O
FIELD
ACV
W1 OFF
+-
PERMANENTMAGNET 2
GENERATOR
PORT C

HYD MOTOR-GENERATOR SEAL DRAIN
HOT BAT. BUSHYD GEN 28V
123
04
DC POWER
PRESS
HYD GEN28V DC POWER
PSI X 1000
115V AC L BUS
115V AC L BUS L 115V AC
SENSED3O SAWTOOTHTRANSFER BUS
VOLTAGE
115V AC L BUSB
HALF-WAVEWAVE HYD GEN DC
DIVIDER RECTIFICATION SHAPING VOLT SENSE
OUTPUT
ERRORSENSING
VOLTAGE ZENER REF &
115V AC L
OUTPUT & PULSE
VS GEN BUILD UP XFER BUS RLY
FREQUENCY WIDTH MOD HYD GEN DC VOLTS
115V AC R BUS3 PHASE
POWER TO  HYD GEN AC VOLTS
FULL-WAVE 115V AC R BUS
OUTPUT AMP  HYD GEN R 115V AC
RECTIFICATION AC VOLTS
TRANSFER BUSSENSE
115V AC R BUS
SQUARE WAVESENERATOR
5.05 A
HYD GEN
DETECTOR VAL (W) (SH 1)
PHASE SHIFTNETWORK
115V AC R LATCHNVM
XFER BUS RLYHYD GEN
IN AIR
SERVO +
ON (W)
SPEED DOWNFILTER &

ONLY SPEED UP DC AMP 115V AC R BUS
POWER READY
CAPTAIN C RESET RETURN L/R EICAS CMPTR
115V AC R BUS
115V AC D RESET SIGNAL
FLIGHT INSTCONTACTOR RETURN
115V AC R BUS XFER BUS GENERATOR CONTROL UNIT E
F
HYD RETURN115V AC INSTR
XFER RLY

HYD PRESSURE
Hydraulic Generator Control Schematic
Figure 2 (Sheet 2)

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MAINTENANCE MANUAL

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