Electrical

Table of Contents:

Normal Operations:
  • Establish External Power
  • Establish APU Power

Alternate Operations:
  • CSD/IDG Disconnect
  • CSD Does Not Disconnect
  • CSD/IDG Oil Light Illuminated
  • Gen Brg Failure Light Illuminated
  • Generator Field Off and/or Gen Open Light(s) Illuminated
  • Bus Tie Open Light Illuminated
  • Galley Power Trip Off Light Illuminated
  • Essential Bus Off Light Illuminated
  • Generator Breaker Will Not Close When Attempting to Parallel
  • APU or External Power Will Not Disconnect Automatically When Attempting To Connect An Engine Generator
  • APU or External Power Will Not Connect To Sync Bus
  • APU No Gen Cooling Light Illuminated
  • Failed TR Unit, DC Ammeter Reads Zero
  • KW Oscillation Between Paralleled Generators (Load Shuffling)
  • KW / KVAR Indications Unbalanced

Controls and Indicators:
  • Constant Speed Drive Controls
  • Generator Controls
  • AC Power Indicators
  • DC Power Controls and Indicators
  • Radio Master and Galley Power Controls
  • Main/APU Generator Fault Annunciator
  • External Power Controls (SP Airplanes)
  • APU Electrical Controls (SP Airplanes)
  • External Power Controls
  • APU Electrical Controls
  • Standby Power Controls

Schematics:
  • Electrical Power System
  • Electrical Power System - 2 APUS
  • Electrical Power System - SP Airplanes
  • Standby Power
  • CSD and Generator
  • Integrated Drive Generator

Supplementary Information:
  • AC Power System
  • DC Power System
  • Auxiliary Power System






Normal Operations

Establish External Power:

External Power AC CONN lights -         Illuminated
AC Meters -                                             Check
External Power 1 Breaker Switch -       CLOSE
Auxiliary Power Ammeter -                    Check
External Power 2 Breaker Switch -       Close
Auxiliary Power Ammeter -                    Check


Establish APU Power:

APU FIELD OFF Lights                             Both Extinguished
AC Meters                                                   Check
APU Generator 1 Breaker Switch            Close
Auxiliary Power Ammeter                          Check
APU Generator 2 Breaker Switch            Close
Auxiliary Power Ammeter                          Check


Alternate Operations

CSD/IDG Disconnect:
Note: CSD/IDG cab only be reset on the ground.
Caution: Do not activate CSD/IDG disconnect switch when engine speed is below minimum ground idle.  CSD/IDG may be damaged as a result of an incomplete disconnect.

CSD Does Not Disconnect
CSD/IDG Oil Light Illuminated
Gen Brg Failure Light Illuminated
Generator Field Off and/or Gen Open Light(s) Illuminated
Bus Tie Open Light Illuminated
Galley Power Trip Off Light Illuminated
Essential Bus Off Light Illuminated
Generator Breaker Will Not Close When Attempting to Parallel
APU or External Power Will Not Disconnect Automatically When Attempting To Connect An Engine Generator
APU or External Power Will Not Connect To Sync Bus
APU No Gen Cooling Light Illuminated
Failed TR Unit, DC Ammeter Reads Zero
KW Oscillation Between Paralleled Generators (Load Shuffling)

KW / KVAR Indications Unbalanced:
If difference between KW meter readings or KVAR meter readings for paralleled generators exceeds 10 KW or 20 KVAR operate the affected generator isolated.


Controls and Indicators

Constant Speed Drive Controls:


CSD/IDG Disconnect Switch:
GUARD DOWN - Normal operation
DISCONNECT - Mechanically disconnects CSD/IDG from engine.  Reset only on ground.
Generator breaker trips.

CSD/IDG Oil Temperature Indicator:
Normally reads temperature of oil leaving CSD/IDG (Oil Out).  With CSD/IDG oil temperature rise switch pressed, indicator reads oil temperature rise through CSD/IDG.

CSD Oil Pressure Light (Amber):
Illuminates when CSD oil pressure low.

CSD/IDG Oil Temperature Rise Switch:
When pressed, indicator reads CSD/IDG RISE temperature.









Generator Controls:


Split System Breaker (SSB) Switch:
TRIP - Opens circuit dividing electrical system into seperate two-generator parallel systems.  Trips automatically to isolate one half of sync bus from sync bus faults, and when two auxiliary generators power sync bus.  SSB may be tripped manually if desired.
CLOSE - Connects sync bus for generators 1 and 2 to the same bus for generators 3 and 4.

Split System Breaker Open Light (Green):
Illuminated - indicates split system breaker open.

Bus Tie Breaker Switch:
TRIP - Disconnects AC bus from sync bus.  Trips automatically due to electrical faults.  Recloses automatically after generator breaker trips.
CLOSE - Restores bus to sync bus and extingushes BUS TIE OPEN light.

Bus Tie Breaker Open Light (Amber):
Illuminated - AC bus disconnected from sync bus.

Generator Breaker Open Light (Amber):
Illuminated - Generator disconnects from its AC bus.

Generator Breaker Switch:
TRIP - Generator disconnected from its AC bus.  Trips due to CSD disconnect, engine shutdown, CSD disconnect, engine shutdown, CSD or electrical faults, APU or external power breaker closed.
CLOSE - Connects generator to its respective bus.  Trips external or APU power if connected to sync bus and initiates automatic paralleling.

Generator Field SwitchL
TRIP - Deactivates generator field and trips generator breaker.  Trips automatically due to electrical faults and when fire switch pulled.
CLOSE - Restores power to generator field and extinguishes FIELD OFF light.

Generator Field Off Light (Amber):
Illuminated - indicates generator field deactivated.

Generator Bearing Failure Light (Amber):
Illuminated - Indicates impending generator bearing failure.



AC Power Indicators:


KVAR Switch:
Press to read KVAR on all KW/KVAR meters.

Essential Power Switch:
Selects power source for the essential AC bus.  External or APU can supply essential AC power if connected to the sync bus when generator 4 bus tie breaker is closed and essential AC bus switch is selected to NORMAL.

Essential Bus Off Lights:
Illuminated - indicates the essential AC bus is not powered.

AC Voltmeter:
Indicates voltage output of the selected generator and PMG when test switch pressed.

Frequency Meter:
Indicates frequency (Hz) output of the selected generator and CSD RPM when generator test switch pressed.

Generator Test Switch -
Press in conjunction with selected engine driven or APU generator AC meter switch to read permanent magnet voltage (PMG) on the AC voltmeter and CSD rpm on the frequency meter.  If an APU generator is selected CSD rpm reads zero.

AC Meters Switches (Blue):
Press to select generator read out on AC voltage and frequency meters.
White ON light illuminates in depressed switch.










DC Power Controls and Indicators:



DC Voltmeter:
Indicates DC voltage at the selected source.

DC Ammeter:
Indicate DC current output of selected source.

DC Meters Switches (Blue):
Press to read voltage and amperage on DC meters.  White ON light illuminates in depressed switch.

Battery Switch:
ON - Battery serves as back up to supply battery bus.  DC Standby bus and static inverter in event of essential power failure.
OFF
- Battery isolated from all loads except hot battery bus
- Battery continues to receive charge
- APU auotmatically shuts down





DC Bus 1 Isolation Switch (As installed):
OPEN - DC Bus 1 isolated
CLOSE - DC Bus 1 paralleled with DC buses 2,3 and essential if other switches closed.

DC Essential Bus Isolation Switch:
OPEN - Essential DC bus isolated.
CLOSE - Essential DC bus paralleled with DC bus 3 and buses 2 and 1 if other isolation switches closed.

DC Bus Isolation Relay Open Light (Green):
Iluminates when corresponding isolation relay is open.



Radio Master and Galley Power Controls

Essential Radio Bus Switch:
ON - Connects essential radio busses to airplane AC and DC essential buses.
OFF - Remove power from essential radio bus.



Galley Power Bus Switches:
ON - Gally power bus connected to airplane bus.

Generator Mode Switch:
NORM - Automatically limits galley power to 80 KVA during 3 generator or less operation.
OVRD - Gally power limit increased to 120 KVA
REDUCED - Limits galley pwer to 80 KVA

3 Gen Mode Light (Amber):
ILLUMINATED:
- 3 main generators or less operating
- Main generator breaker(s) open
- APU or EXT PWR



Main/APU Generator Fault Annunciator


Annunciator Lights:
Provides readout or main and APU generator faults.
Fault circuitry delivers a signal to the annunciator module.
The associated annunciator light illuminates only while read switch pressed.


Annunciator Read Switch:
Press for annunciator reading.
If a fault signal is present at module, the appropriate light illuminates.
The light extinguishes when switch released.


Annuciator Reset Switch:
Press simitaneously with read switch.
If fault signal no longer present, the circuitry clears the fault read out.




External Power Controls (SP Airplanes)


APU Electrical Controls (SP Airplanes)




External Power Controls


External Power On Bus Light (Green):
Illuminated - external power breaker closed, power on sync bus.

External Power Connected Light (White):
Illuminated - External power connected to airplane.
Ground handling busses will be powered by external power.










APU Electrical Controls


APU Generator Field Switch:
TRIP - Field de-energized, generator is deactivated.  Trips automatically die to generator faults when APU FIRE switch is pulled or if other power source is connected to sync bus.
CLOSE - Field energized.  Ground handling buses (Lower Cargo handling) are powered by APU GEN 1 if external power 1 is not connected.  On cargo airplanes main deck cargo handling bus is powered by APU GEN 2 if external power 2 is not connected.




Note:  APU lights will not illuminate unless APU Master Switch is On.
Note: The Main Deck Cargo Handling Bus is powered from APU Generator 2 (or Ext Power 2) only.  The Lower Cargo Handling busses are powered from APU Generator 1 (or Ext Pwr 1) only.


Standby Power Controls:

Standby Power On Light (Green):
Illuminated - Indicates essential AC power lost and the static inverter has been turned on.

Ess Bus Off Light (Amber):
Illuminated when essential AC power lost.

Standby Power Switch:
NORMAL - normal position for flight.  Static inverter automatically powered in the event of essential AC or DC power failure.  If essential power fails, the main airplane battery powers the battery bus, standby DC bus and static inverter.  Static inverter in turn powers the standby AC bus.
OFF - Standby power system deactivated.
MANUAL ON - Ess AC and DC busses disconnected from Standby AC and DC busses.  Static Inverter turned on by battery bus and powers the standby AC bus.  Standby DC bus powered by the battery bus.


(For switch without "Manual On"):
Standby Power On Light (Green):
Illuminated - Indicates standby power switch ON

Standby Power Switch:
ON - Essential AC and DC busses disconnected from standby AC and DC busses.  Static inverter turned on by battery bus powered and powers the standby AC bus.  Standby DC bus powered by the battery bus.  (Battery must be switched on).
OFF - Standby power system powered from essential busses.



Schematics:
Electrical Power System
Electrical Power System - 2 APUS
Electrical Power System - SP Airplanes
Standby Power
CSD and Generator
Integrated Drive Generator


Supplementary Information

AC Power System:

Primary AC power is supplied by four engine driven generators, controlled and monitored from the control cabin.

Generators:
The generators are rated 60 KVA (57KW), 115V, 400Hz (Hertz cycles per second).
They are identical to and interchangeable with APU generators.

Constant Speed Drive:
Each engine driven generator connects to its engine through a CSD.  The CSD maintains a constant generator speed throughout the normal operating range of the engine.  This provides a constant generator frequency output.  Each CSD is a complete self-contained unit consisting of oil supply, cooler, instrumentation and disconnect.
The integral disconnect device provides complete mechanical isolation of the CSD and generator from the engine in the event of a malfunction.

Constant Speed Drive (CSD) / Integrated Drive Generators (IDG):
Each engine driven generator is connected to its engine through a CSD.  The generator and drive unit together are called IDG.
The CSD / IDG maintains a constant generator speed throughout the normal operating range of the engine.
This provides a constant generator frequency output.  Each CSD/IDG is a complete self-contained unit consisting of oil supply, cooler, instrumentation and disconnect.  The IDG uses drive oil for cooling.  The IDG oil system also lubricates the generator bearings.
A heat exchanger cools the oil using engine fan air.
The disconnect device provides complete mechanical isolation of IDG/CSD and generator from the engine in the event of a malfunction.

Controls:
Generators activate by closing the associated generator field switches.
Power from the main busses is obtained by closing the generator breaker switches, which connect generator output to the individual AC busses.
The main AC busses connect to the synchronous bus by bus tie breakers for parallel operation.
The synchronous (sync) bus is provided with a split system breaker which allows physical division of the generator system into two sync busses.
The generators can be paralleled in any combination, any generator or combination of generators can power the buses of a dead generator, or a bus or busses may be operated isolated.
System protection prevents generator connection to the sync bus until voltage and frequency are within limits and prevents the paralleling of unlike power sources.

KW / KVAR Indicators:
Combination KW/KVAR indicators indicate the real and reactive loads produced by the engine driven generators:
KW - The measure of real power delivered.  Balanced indicators among all generators indicates normal functioning of the load controllers and CSDs.  One higher than the others indicates the generator is contributing more than its equal share of the load and should be isolated to supply only its own bus loads.
KVAR - An indication of the amount of reactive load on the generator.  Balanced readings ensure voltage regulators are functioning properly.
The system is automatically protected from out of tolerance conditions.

Essential AC Bus:
Normally, the 115V AC Bus No. 4 powers the 115V AC essential bus.
It may also be powered from the other three generators by using the essential power selector switch. 
The essential AC bus will still receive power from selected generators 1, 2 or 3 with generator breakers open.
Generator breaker No. 4 must be closed to power the essential AC bus from main generator No. 4.

Generator Bearing Failure Detection Lights:
Illumination of a generator bearing failure light indicates excessive generator bearing clearance exists in the associated main airplane or APU generator.


DC Power System:

Primary DC power is supplied to the DC buses from the 115V AC buses through transformer-rectifier (T-R) units.  The batteries provide secondary DC power.

Transformer Rectifiers:
Six T-R units supply DC power to DC buses 1, 2, 3 and Essential DC bus, the DC Gound Handling Bus and the DC Main Deck Cargo Handling Bus.

DC Bus Isolation:
Isolation relays isolate a DC bus or busses as desired.
DC busses 1,2,3 and Essential may be operated in parallel.
Automatic isolation of busses 1 and 2 from bus 3 and Essential occurs when the Essential AC power switch is moved from the NORMAL position.
In this situation the No. 3 DC bus isolation relay opens (the switch does not move) and the associated OPEN light illuminates.

Battery Power:
Two 24V batteries supply DC power.
The airplane and APU batteries are identical and interchangeable.
Because of its location in an unpressurized area in the aft fuselage, the APU battery is provided with an electrically heated blanket to prevent freezing.

Battery Charger:
Independant battery chargers maintain the charge in the two batteries when the 115 V AC Ground Service bus is powered.
The battery chargers are capable of charging a completely discharged battery to a full charge in one hour.
Initial charge will produce a large positive deflection of the needle in the DC ammeter which will decrease as the battery approaches full charge.
After the battery reaches full charge, the charger maintains a reduced charging rate sufficient to sustain a fully charged battery.
Batteries are protected from overheating during charging.
A thermal switch disconnects the charger from the Ground Service bus when battery overheat is sensed.
A battery failure can result in electrical smoke or fumes in the cockpit, low battery voltage and high amperage.
Failure of a battery cell may not create enough heat to trigger the thermal disconnect switch.
Pulling the Battery circuit breaker isolates the battery.
The battery charger powers the hot battery bus and the battery voltage indication will be normal.

Standby Busses:
Standby AC and DC busses are normally supplied by essential AC and DC buses.
If essential AC bus is inpowered, essential DC bus powers standby AC bus through the static inverter when the standby power switch is in either NORMAL or MANUAL ON position.
If essential DC bus is unpowered, the main airplane battery powers the standby DC bus directly and the standby AC bus through the static inverter when the standby power switch is in either the NORMAL or MANUAL ON position.

Galley Power Busses:
Gally busses are powered from the main airplane AC busses.
The galley feeder circuit protection system trips off galleys and illuminates appropriate galley TRIP OFF lights when:
- Current demand from an APU generator or external power source exceeds a safe value.
- There is an electrical fault in the feeder circuit.
- The galley feeder current exceeds a safe value.
The protective system is reset by cycling the appropriate galley power switches.
During APU starter engagement with APU start selector switch in TRU position, power to aft galley (bus 3) is transferred to the APU start T-R unit.
The No. 3 galley feeder circuit protection system then protects APU start feeders.
A fault is indicated by steady illumination of No. 3 galley power TRIP OFF light.

Radio and Flight Instrument Busses:
Essential radios and flight instruments are powered from essential AC and DC busses and No. 2 radios from No. 2 AC and DC busses.
Flight instruments are tied directly to the bus and are not switchable.
Radios are powered when radio master switches are on and AC/DC power is available from the respective bus.
The power source for essential radio and flight instruments is determined by the position of the essential power selector switch.


Auxiliary Power System:

The auxiliary power system consists of the APU and external power units.

External Power:
Two external power receptacles are located in the lower nose section on the right side of the fuselage.
Connecting external power to the sync bus trips the APU or airplane generator breakers if those units are powering the sync bus at the time.
Paralleling of two external power generators is prevented by the split system breaker.

External Power T-R:
A T-R unit is provided to convert AC from the 115V AC ground handling bus to power the 28V DC ground handling bus.

APU Power:
One APU driving two AC generators provides auxiliary power for operation of electrical and pneumatic systems when the airplane engines are not running.
They are rated at 90KVA due to greater cooling supply.
The paralleling of two APU generators is prevented by the split system breaker.
If external power is connected to the sync bus when APU generator power is applied, the externa power breakers will trip; however, external power will retain priority over the ground handling relay and will power the ground handling buses.
Note:  If the airplane is to be powered by only one external power unit or one APU generator, use number one in both cases.  Niether number two external power unit nor APU generator number two can power the ground handling buses.


Limitations - Electrical system:

AC: 115  +/- 5V. 400 +/- 5 Hertz. 

DC Batt & TR: 25-32V.

APU Batt: 25-36V.  

APU Ext: 250 Amps

Gen Isolated:

54KW (81KW 5mins). 3-4 Gen Paralleled: 51KW. 2 Gen Para: Total 81KW. 

Load Spread 10 KW / 20 KVAR.

TR Loads:

Cont: 75 Amps, 30mins: 93 Amps, 5mins: 113 Amps, No Air Flow: 54 Amps. 

CSD Max Oil Temp: 145C.





Standby Power:  Systems powered =  "HAINES1 "

HSI Captain's

ADI Captain's

Ignition

N1

EGT

Standby Gyro

VHF 1








Rear of cockpit - spare bulb cabinet














Overhead Top Circuit Breaker Panel











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