B767/24/101
Electrical Power
Boeing 767-200/300
Electrical Power
Training manual
For training purposes only
LEVEL 1
ATA 24
page 1
13 - 04 - 2012
rev : 1
B767/24/101
Electrical Power
Training manual
This publication was created by Sabena technics training department, Brussels-Belgium, following ATA 104 specifications.
The information in this publication is furnished for informational
and training use only, and is subject to change without notice.
Sabena technics training assumes no responsibility for any
errors or inaccuracies that may appear in this publication.
No part of this publication may be reproduced, stored in a retrieval system, or transmitted, in any form or by any means,
electronic, mechanical, photocopying, recording, or otherwise,
without the prior written permission of Sabena technics training.
Contact address for
course registrations
course schedule information
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Electrical Power
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TABLE OF CONTENTS
1. ELECTRICAL SYSTEM SUMMARY. .......................................................... 6
1.1. External Power. ...................................................................................... 6
1.2. Integrated Drive Generator System....................................................... 10
1.3. IDG Cooling and Control. .................................................................... 12
1.3.1. GE CF6. ....................................................................................... 12
1.3.2. PW 4000. .................................................................................... 14
1.4. IDG Temperature Monitoring. .............................................................. 16
1.4.1. GE CF6. ....................................................................................... 16
1.4.2. PW4000. ..................................................................................... 16
1.5. DC Power System. ............................................................................... 18
1.6. System Control and Indication. ............................................................ 18
1.7. AC Power System. ............................................................................... 20
2. ELECTRICAL SYSTEM PANELS. ............................................................. 22
2.1. Electrical System Control Panel (P5). ..................................................... 22
2.2. Auxiliary Electrical System Control Panel............................................... 24
2.3. Ground Service/Misc Test Panel. ........................................................... 26
B767/24/101
Electrical Power
LIST OF ILLUSTRATIONS
AC POWER INDICATION......................................................................................................... 34
APU GENERATOR EXTERNAL DETAILS .................................................................................... 31
AUXILIARY ELECTRICAL CONTROL PANEL .............................................................................. 25
DC POWER INDICATION......................................................................................................... 18
ELECTRICAL SYSTEM ............................................................................................................. 21
ELECTRICAL SYSTEM CONTROL PANEL .................................................................................. 23
EXTERNAL POWER PANEL ...................................................................................................... 29
GROUND SERVICE / MISC. TEST PANEL .................................................................................. 27
HYDRAULIC MOTOR GENERATOR SYSTEM ............................................................................ 33
IDG AIR / OIL COOLING.......................................................................................................... 15
IDG FUEL / OIL EXCHANGER .................................................................................................. 13
INTEGRATED DRIVE GENERATOR SYSTEM .............................................................................. 11
MAIN AND APU BATTERY CHARGING SYSTEM ...................................................................... 19
POWER DISTRIBUTION ............................................................................................................. 7
POWER DISTRIBUTION - GENERAL............................................................................................ 9
TRANSFORMER RECTIFIER UNIT.............................................................................................. 19
3. AC EXTERNAL POWER SYSTEM. .......................................................... 28
3.1. System Description............................................................................... 28
4. APU GENERATOR.................................................................................. 30
4.1. Physical Description.............................................................................. 30
5. HYDRAULIC MOTOR GENERATOR SYSTEM. ....................................... 32
5.1. System Description............................................................................... 32
5.2. AC Power Indications. .......................................................................... 34
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ABBREVIATIONS AND ACRONYMS
ACMP
ADF
AFT
Agcu
Agb
ALT
AOA
APB
APU
BAT
BITE
BPCU
BTB
CB
CHGR
CMD
COMM
CONT
CSD
CT
CTA
CTR
DCTCU
DME
DPCT
EADI
EAROM
EEC
EFIS
EHSI
EICAS
ELCU
ELEC
EMI
EQUIP COOL
EP
EPC
EPREQ
EXT
FCC
Alternating Current Motor Pump
Automatic Direction Finder
Afterwards
Apu Generator Control Unit
Accessory Gearbox
Altitude
Angle Of Attack
APU Breaker
Auxiliary Power Unit
Battery
Built In Test Equipment
Bus Power Control Unit
Bus Tie Breaker
Circuit Breaker
Charger
Command
Communication
Control(ler)
Constant Speed Drive
Current Transformer
Current Transformer Assembly
Center
DC Tie Control Bus
Distance Measurement Equipment
Differntial Protection Current Transformer
Electronic Attitude Direction Indicator
Electrically Alterable Read Only Memory
Electronic Engine Control
Electronic Flight Instrument System
Electronic Horizontal Situation Indicator
Engine Indicating and Crew Alerting System
Electrical Load Control Unit
Electric(ally)
Electromagnetic Interference
Equipment Cooling
External Power
External Power Contactor
External Power Request
External
Flight Coltrol Computer
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FLT
FMCS
FWD
GCB
GCR
GCU
GEN
GHB
GHR
GND
GSB
GSSR
GSTR
HF
HMG
HYD
IAS
IDG
ILS
IND
INTLK
INTPH
IRU
ISLN
LAV
Lct
LRU
LTS
MAN
MPU
Nct
NVM
OF
OV
OVHD
Pdp
PDT
PMG
PNL
POR
Flight
Flight Management Computer system
Forward
Generator Control Breaker
Generator Control Relay
Generator Control Unit
Generator
Ground Handling Bus
Ground Handling Relay
Ground
Ground Service Bus
Ground Service Select Relay
Ground Service Transfer Relay
High Frequency
Hydraulic Motor generator
Hydraulic(ally)
Indicated Airspeed
Integrated Drive Generator
Instrument Landing System
Indicator
Interlock
Interphone
Inertial Reference Unit
Isolation
Lavatory
Line Current Transformer
Line Replaceable Unit
Lights
Manual
Magnetic Pick Up
Neutral Current Transformer
Non-Volatile Memory
Over Frequency
Over Voltage
Overhead
Power Distribution Panel
Pole Double Throw
Permanent Magnet Generator
Panel
Point Of Regulation
PST
PWR
QAD
RCCB
RDMI
REF
SENS
STBY
TEMP
TR
TRU
UBR
UF
UTIL
UV
VHF
VOR
Vr
VSI
XFER
XFMR
Pole Single Throw
Power
Quick Attach Detach
Remote Control Circuit Breaker
Radio Distance Magnetic Indicator
Reference
Sensor
Standby
Temperature
Transformer Rectifier
Transformer Rectifier Unit
Utility Bus Relay
Under Frequency
Utility
Under Voltage
Very High Frequency
VHF Omnidirectional Range
Voltage Regulator
Vertical Speed Indicator
Transfer
Transformer
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Electrical Power
1. ELECTRICAL SYSTEM SUMMARY.
1.1. External Power.
The external power system allows 115 volt ac ground power to be connected
for powering the ground handling, ground service, and left and right main ac
buses. An external power source is connected to the external power
receptacle located in the P30 panel. Other external power components are
located in the main equipment center P34, P33 panels and E2 rack. If the Bus
Power Control Unit (BPCU) senses good power quality the AC CONNECTED
and PWR NOT IN USE LIGHTS (P30) and AVAIL LIGHT (P5) are illuminated.
The BPCU initiates opening and closing of the external power contactor,
ground handling relay, and ground service select and transfer relays.
It provides external power monitoring for fault isolation and contains BITE for
the complete electrical system. The ground handling bus is automatically
powered for good external power quality, and external power is given priority
over APU generator power. The ground service bus receives power
automatically when the right main AC bus is powered. When the right main
bus is not powered, pushing the GROUND SERVICE switch (P21 forward
attendants panel) allows the ground service bus to be powered either from
external power or APU generator. Pushing the EXT PWR switch (P5 overhead
panel) closes the external power contactor and the EXT PWR ON light
illuminates. External power has priority over the integrated drive generator
(IDG) and APU generator when manually selected. After both generator
circuit breakers close, the external power contactor is tripped open.
The BPCU protection circuitry monitors external power current, voltage and
frequency for fault isolation tripping of the external power contactor, ground
handling relay and ground service select and transfer relays. External power
contactor fault protection trips are reset by pushing the EXT PWR switch.
Ground handling and ground service system fault protection trips are reset by
pushing the GROUND SERVICE switch.
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Power Distribution.
Each power feeder includes a length of high temperature copper wire and a
length of light weight aluminium wire spliced together. Copalum splices are
used to connect the copper and aluminium wires together. The IDG power
feeder splices are located in the upper part of the nacelle strut. The APU
generator power feeder splices are located between the APU firewall and the
rear pressure bulkhead. The all copper external power feeder is one piece.
The IDG power feeders can only be disconnected at the IDG terminal block.
For the APU generator, power feeders are disconnected at either the firewall
or the generator terminal block.
The tie bus feeders interconnect the main power panel distribution centers
through the bus tie breakers. Connections are provided to the auxiliary power
breaker and the external power contactor. Tie bus feeders between BTB’s,
APB and EPC are connected in a ring-bus configuration.
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R
ELCU
T
L - AC BUS
UTIL
BUS
RLY.
LIDG
EXTERNAL
POWER
LGCB
L - XFR.
BUS RLY.
BPCU
GCU
L
LBTB
ALT.
INST. BUS
VOLT SENS.
DC TIE
RLY
HYD. GEN.
DC PWR. RLY.
APU
GEN
APB
ALT.
INST. BUS
VOLT SENS.
APU
GCU
GCU
R
RBTB
NORM.
28V AC BUS
RIDG
UTIL
BUS
RLY.
RGCB
28V AC BUS
R - AC BUS
ELCU
T
R. - 28V DC BUS
G
A
L
L
E
Y
O
F ON
F
W
L
GEN
CONT
BUS
OFF
L BUS
ISLN
W
AUTO
BUS TIE
OFF
AUTO
W
R
OFF
ON
W
DRIVE
W
W
DRIVE
GEN DRIVE DISC
L
R
OFF
ON
L
UTIL BUS
W
O
ON W
F ON
F
AVAIL
W
O
F
F
W
O
F ON
F
W
R
GEN
CONT
BUS
OFF
R BUS
ISLN
AUTO
BUS TIE
BAT
STBY POWER
APU GEN EXT PWR
MAIN BAT APU BAT
DISCH
DISCH
OFF
ON W
BAT
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Electrical Power
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GND.
HND.
RLY.
AC GND. HND. BUS
28V AC GND.
SVC. BUS
LOAD
SHED.
RLY.
GND.
SVC.
SELECT.
RLY.
AC GND. SVC. BUS
GND.
SVC.
XFR.
RLY.
R
DC GND. HND. BUS
APU BATT.
CHGR. RLY.
GND. SVC. EXT. BUS
MAIN BATT.
CHGR. RLY.
TO MAIN
BATT.
CHGR.
APU
BATT
CHGR
APU BATT. BUS
POWER DISTRIBUTION PANEL (ON P5)
APU CRANCK
CTCTR
R - UTIL BUS
R - XFR. BUS
HMG
R - XFR.
BUS RLY.
AC
DC
TO MAIN APU
BAT. TIE RCCB
TO APU
STARTER
MOTOR
POWER DISTRIBUTION
EPC
NORM.
INST. XFR.
BUS RLY.
CAPT FLT INST. XFR. BUS
C - BUS
XFR. RLY.
C - 115V AC BUS
F/O FLT INST. XFR. BUS
L - XFR. BUS
INV.
STAT
AC STBY.
PWR. RLY.
AC STBY BUS
C. - 28V DC BUS
C - BUS
XFR. RLY.
STBY. PWR.
RLY.
L - UTIL BUS
28V AC BUS
G
A
L
L
E
Y
28V AC BUS
L. - 28V DC BUS
FROM
APU
MAIN APU BAT.
BAT. TIE RCCB
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FROM AC
GND. SERV.
BUS
MAIN
BATT
CHGR
HOT BATT. BUS
MAIN
BATT. RLY.
MAIN BATT.
XFR. RLY.
BATT BUS
DC STBY BUS
Training manual
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S
H
C
I
G
I
N
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H
Y
C
P
E
O
T
C A U
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E
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POWER DISTRIBUTION - GENERAL
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1.2. Integrated Drive Generator System.
The generator outputs 115/200 volt, 3-phase, 400 Hz, ac power and is rated
at 90 KVA.
Each integrated drive generator is QAD ring attached to the accessory
gearbox. Constant generator speed is maintained by a mechanical speed
governor. The disconnect reset ring allows reconnection of the IDG input
spline mechanical connection after a disconnect. Two electrical connectors
provide IDG to GCU interface for control, protection and monitoring. A
terminal block is used for power feeder connections.
The IDG is cooled by an external oil cooling system composed of fuel/oil
and air/oil heat exchanger assemblies connected in series. The fuel/oil heat
exchangers use engine fuel to cool IDG oil. An air/oil heat exchanger receives
fan air through a pneumatic and electrically controlled cooling air shutoff
valve. A generator drive disconnect switch, when pushed, disconnects the IDG
input shaft from the engine accessory gearbox if the associated engine fuel
control switch is not in cutoff.
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INTEGRATED DRIVE GENERATOR SYSTEM
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1.3. IDG Cooling and Control.
1.3.1. GE CF6.
IDG Fuel/Oil Heat Exchanger.
This unit provides primary cooling for the integrated drive generator oil during
normal flight operations.
Location.
The heat exchanger is attached to the accessory gearbox lower right
side.
IDG Air/Oil Heat Exchanger.
The air/oil heat exchanger cools IDG oil when the fuel/oil heat exchanger has
insufficient fuel flow. A cooling air shutoff valve controls fan air flow to the
air/oil heat exchanger.
Location.
The air oil heat exchanger and cooling air shutoff valve are on the
engine compressor case at approximately 4 o’clock.
The air/oil heat exchanger is a tube and fin-type heat exchanger.
Heated oil flows from the inlet port through tubes to the outlet port.
An air supply duct on the engine fan case directs fan air through the
cooling air shutoff valve. The fan air passes over the heat exchanger
fins.
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IDG FUEL / OIL EXCHANGER
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1.3.2. PW 4000.
Purpose.
The IDG Air/Oil Heat Exchanger cools the IDG oil when the Fuel/Oil
Cooler has insufficient capability.
Airflow through the heat exchanger is controlled by the IDG Air/Oil
Heat Exchanger Valve.
The HPC Secondary Flow Control/IDG Air Oil Heat Exchanger Valve
Override Solenoid controls Ps3 pneumatic pressure to the Override Fuel
Pressure Switch.
Location.
The IDG Air/Oil Heat Exchanger and Valve are mounted in the aft side
of the intermediate case at the 4 o’clock position.
The HPC Secondary Flow Control/IDG Air/Oil Heat Exchanger Valve
Override Solenoid and the Override Fuel Pressure Switch are mounted
on the aft side of the intermediate case at the 1 o’clock position.
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IDG AIR / OIL COOLING
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1.4. IDG Temperature Monitoring.
1.4.1. GE CF6.
IDG temperature is monitored by two temperature sensors located
inside the IDG. After processing the GCU sends IDG rise and oil out
temperature to EICAS for display on the ELEC/HYD page.
Operation.
EICAS supplies a dc reference voltage to the GCU’s trough resistor
R10111. The voltage and current of this ref circuit vary with IDG
temperature (1 mA = 180 °C). This changing voltage represents the
IDG temp and is monitored by the EICAS computers.
The K1 timer module located in the P61 panel signals the GCU to
transmit either oil out or rise temp. The same signal is used to inform
EICAS which temperature is being transmitted by the GCU.
If the K1 timer should fail in the ground (rise temp) or open position
(outlet temp) for longer than 5 seconds EICAS will blank the failed
temperature indication for both IDG’s.
Indication.
IDG oil out and rise temp are displayed on the ELEC/HYD page.
The GCU alternately transmits oil out and oil rise temperature sensor in
one of the following ways :
- Both temp sensors failed. Transmit 180 °C for oil out and rise
temp.
- Oil in or oil out temp sensor failed. Set rise temp to 8 °C if
engine is running or 0 °C if engine is not running.
- Oil out temp sensor failed. Oil out indication will be oil in + 8 °C
with engine running and oil in temp with engine not running.
- Oil in temp sense failed. The GCU uses oil out - 8 °C for oil in.
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1.4.2. PW4000.
Operation.
The generator control unit monitors the IDG inlet and outlet oil
temperature sensors located in the IDG.
The sensors are temperature bulbs whose resistance varies with oil
temperature.
Each sensor is read by the microprocessor through an analog-to-digital
converter. The signals are converted to temperature units in °C.
The generator control unit provides IDG oil temperature signals to both
EICAS computers for display on the EICAS ELEC/HYD maintenance page.
A dc reference voltage is supplied by each EICAS computer.
The generator control unit controls the current flow based on IDG
outlet and rise temperature.
Current flow varies up to a maximum of 1 ma.
A voltage divider is used to send a voltage to each EICAS computer.
This voltage is compared with the dc reference voltage to compute
either IDG OUT or IDG RISE temperature.
The data is displayed from 0 to 180 °C.
The K1 TIMER module located in the P61 panel change’s the
information requested every 0.5 second (from open - to closed then
back to open) .
The closed circuit discrete represents a request for IDG RISE
temperature and the open condition a request for IDG OUT
temperature.
Real time updating occurs 200 msec after the IDG OUT temperature
discrete is sensed.
Each outlet temperature pulse normally resets and starts a 5 second
counter. If the discrete ceases for greater than 5 seconds, the, opposite
value of IDG OUT temperature or IDG RISE temperature for both IDG’s
goes blank. The remaining displayed value is continuously updated.
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Training manual
1.5. DC Power System.
The dc power system supplies loads requiring dc power. Both transformer
rectifier units (TRU) are located in the main equipment center.
The main battery, battery charger and static inverter are located in the main
equipment center. An APU battery and battery charger are located in the aft
equipment center.
The main battery/battery charger system provides dc power for the standby
and autoland systems. A separate APU battery/battery charger system
supplies power for APU starting. Both batteries are 40 amp-hour, 20 cell
nickel-cadmium, rated at 24 volt dc. In the charge mode, battery charging is
constant current and temperature compensated. A thermistor and thermal
switch, both integral to the battery, provide temperature sensing and
overtemperature protection signals for charger control and shut-down.
In the transformer rectifier unit mode, the battery charger supplies constant
voltage. The standby system static inverter supplies single phase AC power
for the ac standby bus. The BAT switch controls back-up dc input inverter
power and the STBY POWER rotary switch controls auto/manual standby
modes. Each TRU normally supplies its own dc load buses. An automatic
operating dc tie control unit allows a single TRU to supply both main dc
buses. A remote control circuit breaker (RCCB)
automatically closes during standby power system operation tying the main
and APU battery buses together.
1.6. System Control and Indication.
Manual or automatic source selection is provided during ground and inflight
operations from the electrical system and auxiliary electrical system control
panels located in the flight compartment. Electrical system monitoring is
displayed on EICAS.
DC POWER INDICATION
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TRANSFORMER RECTIFIER UNIT
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B767/24/101
Electrical Power
MAIN AND APU BATTERY CHARGING SYSTEM
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Training manual
1.7. AC Power System.
During normal operations, the ac system uses the electrical output of the two
IDG’s, with each IDG powering its associated channel. For ground operations,
external power or the APU generator can power either or both channels.
The APU generator can also be used in flight as a back-up source, should an
IDG fail. The APU generator, mounted to the APU gearbox, is cooled and
lubricated using APU oil. The electrical output of the APU generator is the
same as that of an IDG.
Each GCU (El and E2 racks) automatically controls and protects an individual
generating channel by monitoring source output from IDG or APU generator,
serial data link to and from the BPCU and control switch positions.
Main power breakers (P31, P32 and P34) control ac power flow and are all
(except EPC) interchangeable.
B767/24/101
Electrical Power
The hydraulic motor generator (HMG) system provides a back-up source of
electrical power after loss of all generators. An air-driven hydraulic pump
pressurizes the center hydraulic system to power the HMG. The HMG and
shutoff valve are located in the left wheel well. A generator control unit (P65)
performs control and protection functions. A momentary test switch (P61) is
used to perform system check-out. Ac bus transfer relays connect the
captain’s, left and right ac transfer buses to the hydraulic motor generator
AC output. A DC contactor connects the hydraulic motor generator dc
output to the hot battery bus.
Current transformer assemblies monitor current flow for open phase,
differential protection, load monitoring and overload protection.
Electrical load control units and utility bus relays (P31 and P32) connect
nonessential galley and utility bus loads to main ac buses.
A GEN CONT switch controls the associated field relay (GCR) and main power
breaker (GCB or APB). Latching the switch (ON) closes the GCR. Unlatching
the switch (OFF) opens the GCR. If the GEN CONT switch is unlatched, then
the GCR is opened and closed using GEN FIELD switch. With the GEN CONT
switch latched the main power breaker is automatically opened and closed by
the associated GCU. The BTB is automatically controlled by the associated
GCU if the corresponding BUS TIE switch is latched (AUTO). The GCU and
BPCU protective functions monitor system current, voltage, frequency and
input speed for open phase, overvoltage, undervoltage, shorted permanent
magnet generator, underfrequency, overfrequency, shorted rotating diode,
underspeed, differential current and load shedding faults.
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ELECTRICAL SYSTEM
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2. ELECTRICAL SYSTEM PANELS.
Normal operation of the electrical power system is performed at the electrical
system control panel and the auxiliary electrical system control panel.
Both momentary and alternate action pushbutton switches are used on the
electrical panels. The alternate action switches are normally in the latched
(ON) position. This allows automatic operation of the electrical system
breakers and relays under the control of the system’s computers.
Switch indicator lights are powered by the master dim and test system.
2.1. Electrical System Control Panel (P5).
The momentary external power switch controls the position of the external
power contactor. A white AVAIL light indicates power is of proper quality.
The white ON light illuminates when the external power contactor is closed.
The generator control switches provide a control signal which closes the
generator control relay (GCR), and, when proper power is available, enables
automatic closing of the generator circuit breaker (GCB). The flow bar and
ON legend indicate switch position. An amber OFF light illuminates when the
associated generator circuit breaker is open.
The ac bus tie switches allow manual or automatic control of the bus tie
breaker (BTB). When a switch is unlatched, the associated BTB is locked open,
isolating the associated main ac bus from the ac tie bus. In this case, the
AUTO indication is not visible and the amber ISLN light is illuminated.
Latching an ac bus tie switch (ON) enables automatic operation of the
associated bus tie breaker. In this case, the AUTO light normally illuminates
and the ISLN light is off. If the ISLN light illuminates when the bus tie switch is
latched, then a fault has tripped and locked the BTB open.
The alternate action utility bus switches provide manual control of the power
relays connecting utility and galley buses to the main ac buses.
The ON legend is seen when the switch is latched (ON). The amber OFF light
illuminates when the associated utility bus relay (UBR) is open.
Pushing the momentary generator drive disconnect switches causes a
mechanical disconnection between the integrated drive generator and the
engine when the associated engine fuel control switch is not off. An amber
DRIVE light on the switch illuminates for a mechanical failure of the IDG or
when the engine is not running.
The alternate action battery switch controls connection of the battery bus to
the left dc bus or the hot battery bus. The ON legend is seen when the switch
is latched (ON). An amber OFF light illuminates when the battery switch is
unlatched during normal ground and flight operations.
For the main and APU batteries, a dedicated battery discharge light
illuminates if the battery is discharging.
The standby power mode of operation is controlled by the standby power
selector switch. To turn the switch off, push the switch in, when going from
the AUTO to the OFF position. An amber standby power bus OFF light
illuminates when the ac or dc standby bus is unpowered.
An ac BUS OFF indicator light illuminates when the associated main ac bus is
de-energized.
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ELECTRICAL SYSTEM CONTROL PANEL
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2.2. Auxiliary Electrical System Control Panel.
The momentary generator field manual reset switch is pushed to open and
close the generator field control relay when the generator control switch is
unlatched. A white FIELD OFF light illuminates when the generator control
relay (GCR) is open.
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AUXILIARY ELECTRICAL CONTROL PANEL
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2.3. Ground Service/Misc Test Panel.
Ground Service Switch.
A single momentary switch allows the ground service bus to be powered
directly from the APU generator or external power. Pushing the ground
service switch connects or disconnects the APU generator or external power if
the right main ac bus is de-energized.
A light inside the switch illuminates to indicate that the ground service bus is
powered directly from external or APU generator power.
Hydraulic Motor Generator Test Switch.
A momentary toggle switch (EQUIP COOL/HYD GEN) on the right side P61
panel is provided for hydraulic motor generator system testing. When toggled
to the HYD GEN position, the test switch simulates loss of both main ac
buses, and provides a start-up signal to the hydraulic motor generator
system. Release of the test switch causes system shut-down and transfer of
loads back to normal bus sources.
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GROUND SERVICE / MISC. TEST PANEL
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3. AC EXTERNAL POWER SYSTEM.
3.1. System Description.
A ground power source can be connected at the airplane external power
receptacle to supply power to the 767 ac electrical power system. Power is
supplied to main load buses when the external power contactor (EPC) and
corresponding bus tie breakers (BTB’s) close. The external power source also
supplies power to the ground service and ground handling buses, using the
ground service select, ground service transfer, and ground handling relays.
Component Locations.
An external power receptacle (P30 panel) is located on the lower fuselage,
just aft of the nose gear. All other external power system components are
located in the main equipment center. There are two control switches.
An EXT PWR switch is located on the P5 overhead panel, and a ground
service switch is located on the P21 forward attendant’s panel.
The 115 volt ac ground handling bus is automatically powered on the ground
if external power is of acceptable quality. The BPCU controls the three
position ground handling relay and automatically gives external power
priority over the APU generator.
Ground service bus power is supplied to equipment which must be powered
in both air and ground modes. This bus receives power automatically from
the right main ac bus if that bus is powered. If the right main bus is not
powered, pressing the ground service switch allows supply of either external
power or APU generator power (whichever is first available) to the ground
service bus. If both external and APU generator power are available when the
ground service switch is pressed, external power is used.
If a fault exists in the external power circuit, BPCU trips the EPC to protect the
power source and loads.
Operation.
The Bus Power Control Unit (BPCU) controls the EPC. The EPC controls the
flow of external power to the ac tie bus. When external power of acceptable
quality (as determined by the BPCU) is first connected, the AC CONNECTED
and PWR NOT IN USE lights on the P30 panel come on. Also, the AVAIL light
on the EXT PWR switch comes on. Pressing the momentary EXT PWR switch
closes the EPC. When the EPC closes, the ON light on the EXT PWR switch
comes on.
External power always has priority over the IDG’s and APU generator when
manually selected. If both engines are started and the IDG’s are ready to
supply electrical power, then, automatically, the EPC and BTB’s are tripped
open and the GCB’s close. If both engines are operating, and external power
is supplying power to the main buses, cycling the generator control switches
(unlatch-latch) also causes the EPC and BTB’s to trip open and the GCB’s to
close.
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EXTERNAL POWER PANEL
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4. APU GENERATOR.
4.1. Physical Description.
The electromagnetic components of the auxiliary generator are the same as
those used in the IDG and are interchangeable except that the APU generator
is contained in its own magnesium cast housing and has a different input
spline and mounting flange. The generator weighs 61.9 pounds (27.63 kg)
dry weight.
Keyhole slots allow mounting of the generator to the auxiliary power unit
accessory gearbox. An aluminium seal plate is installed between the
generator mounting flange and gearbox drive pad. The mounting flange
incorporates three locating pins to position the generator on the APU flange.
Elastomer compound inserts are installed in the seal plate “OIL-IN” and
“OILOUT” ports. The input shaft incorporates a shear section that shears at
4700 ± 300 in-lbs.
The APU generator is spray oil cooled and lubricated using APU engine oil.
Pressurization, scavenging and filtering of the oil is provided by the auxiliary
power unit. Generator case pressure, 5 psig above ambient, is introduced
from the APU gearbox through a rotating screw passageway in the input
shaft. APU generator oil is filtered by a 20/40 micron filter. The delta pressure
(popout) indicator activates at 20 psid. A mechanical lockout prevents
activation when oil temperature is below 115 °F (46 °C). When the filter delta
pressure reaches 35 psid and oil temperature above 115 °F (46 °C) an APU
shut-down is initiated by the DP switch.
A terminal block with four stainless steel studs provides the feeder
connections. A single electrical connector provides all other electrical
connections.
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APU GENERATOR EXTERNAL DETAILS
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5. HYDRAULIC MOTOR GENERATOR SYSTEM.
The hydraulic motor generator system provides a non-time limited back-up
source after loss of all generator electrical power.
5.1. System Description.
The hydraulic motor generator (HMG) is located in the left wheel well.
The generator is driven by a hydraulic motor supplied from the center
hydraulic system. An air-driven hydraulic pump (ADP), supplied by left or right
engine bleed air, can pressurize the center hydraulic system. A motor driven
hydraulic shutoff valve provides on/off control for the HMG. Automatic
activation of the hydraulic motor generator system occurs with loss of power
to both main ac buses. A flow limiter regulates hydraulic flow to the trailing
edge flaps and leading edge slats during HMG operation. Control and
protection functions are performed by the generator control unit located in
the P65 panel.
A momentary test switch (P61 panel) is provided for system check-out.
The HMG system operational status and electrical parameters are monitored
by EICAS.
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HYDRAULIC MOTOR GENERATOR SYSTEM
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Training manual
5.2. AC Power Indications.
Generator Load.
Each GCU provides a dc voltage output to both EICAS computers
proportional to the associated ac generator channel load. The GCU senses
generator load current from the generator current transformers.
Generator load is displayed on the EICAS ELEC/HYD maintenance page for
values between 0/0.05 to 1.50 (1.OO = 90KVA).
External Power Load.
The BPCU provides a dc voltage output to both EICAS computers
proportional to the external power load. The BPCU senses external load from
the ground power current transformer. The ac load for main ac, ground
service and ground handling buses is displayed for values between 0/0.1 to
1.50 (1.00 = 90KVA) on the EICAS ELEC/HYD maintenance page.
AC Voltage and Frequency.
For each main power source (IDG, APU generator, EXT PWR, and HYD
MOTOR GEN) the voltage and frequency are sensed from phase B. The
singlephase
output of the static inverter is sensed to display voltage and frequency.
All signals are supplied to both EICAS computers except the APU GENERATOR
(L computer only) and HYD MOTOR GEN (R computer only). Indications are
displayed on the EICAS ELEC/HYD maintenance page. AC voltage and
frequency are displayed between 0/100 to 130 volts ac and 0/380 to 420 Hz.
AC POWER INDICATION
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