McDonnell Douglas DC 10 40 Electrical

CHAPTER 6

E L E C T R I C A L S Y S T E M S

Page

TABLE OF CONTENTS 06-00-01/02

DESCRIPTION

General 06-10-01

Description 06-10-01

Controls and Indicators 06-10-02

COMPONENTS

Circuit Breaker Panel Locations 06-20-01/02

Forward and Aft Overhead Circuit Breaker Panels 06-20-03/04

Flight Engineer's Overhead Circuit Breaker Panel 06-20-05/06

Upper Main Circuit Breaker Panel 06-20-06A/06B

Lower Main Circuit Breaker Panel 06-20-11

Miscellaneous Circuit Breaker Panels 06-20-12

CONTROLS AND INDICATORS 06-30-01

FUNCTIONAL SCHEMATICS

Electrical System 06-40-01/02

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E L E C T R I C A L S Y S T E M S

GENERAL

The ac and dc electrical systems arenormally powered by three engine-driven generators. They may also bepowered by an auxiliary power unit(APU)-driven generator or throughtwo external power receptacles (mainand galley). The main externalpower receptacle provides both acand dc power. The galley externalpower receptacle provides only acpower and to obtain full galleypower, APU generator power, enginegenerator power or main externalpower must be on. Portions of thesystems may be powered by a batteryand other portions by an air-drivengenerator (ADG). Distribution andcontrol is effected through controlpanels, annunciators, indicators,switches, buses, and circuit breakers.

: If a circuit breaker trips,a cooling period of about 90seconds should be allowedbefore resetting. A trippedcircuit breaker should neverbe reset more than once.

Operational simplicity and reliabi-lity are provided by protectivecircuitry with automatic correctiveaction included. The electricalgenerating system is ac, withnecessary dc power provided bytransformer/rectifier units or thebattery.

DESCRIPTION

AC ELECTRICAL SYSTEM

AC Generating System

During ground operations, 3 phase,115/200 VAC, 400 Hz power is suppliedby two external power sources, theAPU-driven generator, or by one or

more of the three engine-drivengenerators. In flight, normal poweris furnished by the three engine-driven generators. The generatorswill function either paralleled,unparalleled, or isolated. Frequencycontrol of each engine-drivengenerator is provided by an asso-ciated engine-driven constant speeddrive (CSD) unit. CSD disconnectcan be accomplished at any time (notrecommended when engine is belowidle rpm), but reengagement ispossible only on the ground afterthe engine has come to a completestop. Each generator is capable ofsupplying sufficient power foroperation of all essential electricalsystems.

The APU-driven generator provideselectrical power for ground opera-tions and also serves as a supple-mental power source when required incertain flight phases. The APU-driven generator is identical to thethree engine-driven generators. TheAPU generator does not have a CSD.The APU is governed to drive thegenerator at the correct speed. TheAPU generator cannot be paralleledwith any engine generator or themain external power source.A battery/static inverter combinationcan provide approximately 30 minutesof left emergency ac and dc buspower for the Captain's flightinstruments and essential communica-tion and navigation equipment whennormal sources are inoperative.Emergency ac power for an auxiliaryhydraulic pump or the Copilot'sinstruments on the right emergencyac and dc buses can be supplied bydeploying the ADG and selecting thedesired mode of the ADG controlswitch.

AC Distribution System

Three independent ac channelsprovide power to associated generator

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buses and main ac buses. Parallelingof the channels is accomplishedthrough the ac tie bus. This designpermits assumption of electricalloads by any functioning generator(s).

A fourth, independent ac channelpermits distribution of APU generatorpower to the generator and mainbuses for ground or inflight opera-tions. The two emergency ac busescan be energized by powering gener-ator buses 1 and 3 from any of theengine-driven generators, theAPU-driven generator or the mainexternal power source. An emergencyac source is available to the leftemergency ac bus through the battery/inverter combination. The ADG maybe used to power the right emergencyac bus.

The generator buses and the acground service bus supply most ofthe centrally located and/or high-current loads (hydraulic pumps, mostfuel pumps, ac buses and galleypower). Power for lower current,non-centrally located loads andessential loads is supplied throughthe three main ac buses, cabin acbuses, remote ground service buses,and the two ac emergency buses.Radio and instrument buses supplytheir respective component loads.

The ac ground service bus alsoprovides power to those componentsessential to ground servicingoperations. Energizing the totalnormal distribution system, when thetotal system is not required, isthus avoided. However, poweroriginating at the main externalpower receptacle, the APU-drivengenerator, or one or more of thethree engine-driven generators canbe directed to each of the main acbuses, if required by operationalneeds.

Protective circuitry is provided toautomatically isolate faults.Additionally when no other source isavailable and just one engine-drivengenerator is operating, all busesare automatically connected to thatsource.

DC ELECTRICAL SYSTEM

DC Generating System

Four transformer/rectifiers (T/R's)are the primary source of dc power.The battery and/or the ADG (throughT/R 3) may be used as emergency dcpower sources.

A battery charger keeps the batteryfully charged when the ac groundservice bus is powered, the batterybus is powered by a T/R, and thebattery switch is in BAT. Sensorsin the battery provide protectionand control for the charger.

DC Distribution System

Similar to the ac system, threecounterpart dc channels, originatingin T/R's 1, 2A, and 3, (powered bythe APU generator, the main externalpower source, or an engine generatorvia generator buses 1, 2, and theright emergency ac bus), energizetheir associated dc buses. A fourthchannel, normally originating in T/R2B (powered from the ac groundservice bus by either the APU, themain external power source, or acgenerator bus 2) energizes the dcground service bus. On airplaneswith SB 24-90 incorporated orproduction equivalent, T/R 2A can bemanually selected as an alternatepower source for the dc groundservice bus. Normally, the batterybus is powered from T/R's 2A and 2B.Emergency dc power is available tothe right emergency dc bus from the

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Aug 1/83

ADG through T/R 3. Emergency dcpower is available to the leftemergency dc bus and the battery busfrom the battery. Unlike the acsystem, the dc buses are electricallyisolated. Two or more dc buses canbe operated in parallel, if required,via the dc tie bus by closing theappropriate dc tie switches. Thebattery direct bus is powered at alltimes, regardless of the batteryswitch position..

CONTROLS AND INDICATORS

Controls and indictors required tooperate and monitor the electricalsystems are on the Flight Engineer'sUpper Panel No. 1 and on the Pilot'sOverhead Panel and Glareshield.Illustrations of these major panelsare in Chapter 1. Individual con-trols, circuit breakers, and indica-tors are illustrated and described inanother section of this chapter.

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CIRCUIT BREAKER PANEL LOCATIONS Flight Compartment

FLIGHT ENGINEER'S OVERHEADCIRCUIT BREAKER PANEL

ELECTRICAL SYSTEMRESET PANEL

AFT OVERHEAD CIRCUITBREAKER PANEL

FORWARD OVERHEADCIRCUIT BREAKER PANEL

UPPER MAIN CIRCUITBREAKER PANEL

LOWER MAIN CIRCUITBREAKER PANEL

OVERHEAD INTEGRALLIGHTING CIRCUITBREAKER PANELFLIGHT ENGINEER'SLIGHTING CIRCUITBREAKER PANEL

COPILOT'S CONSOLECIRCUIT BREAKER PANEL CAPTAIN'S CONSOLE CIRCUIT

BREAKER PANEL

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FORWARD AND AFT OVERHEAD CIRCUIT BREAKER PANEL

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FLIGHT ENGINEER'S OVERHEAD CIRCUIT BREAKER PANEL

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UPPER MAIN CIRCUIT BREAKER PANEL (Sheet 3)

LOWER MAIN CIRCUIT BREAKER PANEL

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ELECTRICAL SYSTEM - Controls and Indicators

GEN Switch (1, 2, 3)ON Arms circuit to close associated generator relay(GR) and connects generator to generator bus.OFF Opens associated GR and disconnects

generator from generator bus.RESET This momentary position will close generator

control relay (GCR) if the trip was caused byautomatic operation of protection circuits or byoperating fire handle. RESET is not used in con-junction with GEN FAIL light.

GEN OFF Light (1, 2, 3)Comes on when generator is disconnected from generatorbus. Indicates generator relay (GR) is open. The ELEC cuelight and MASTER CAUTION lights also come on.

GEN FAIL Light (1,2,3)Comes on to indicate impending or actual generatorfailure, or spurious signal. To reset, a GEN FAIL RESETbutton located on Upper Main CB Panel is pushed. If signalwas spurious, GEN FAIL light will go off when reset buttonis pushed.

CSD TEMP Gage (1, 2, 3)Indicates CSD outlet oil temperature on outer scale. In-dicates temperature rise (outlet temperature minus inlettemperature) on inner scale when CSD TEMP PUSH FORRISE button is pushed.

CSD OIL PRESS LO Light (1, 2, 3)Comes on when CSD oil pressure is below allowableoperating limit. The ELEC cue and MASTER CAUTIONlights also come on.

CSD Disconnect button (1, 2, 3)When pushed, disengages CSD. Disconnect is notrecommended when engine is below idle rpm. Once dis-connected, CSD cannot be reset in flight or with the enginerunning on the ground.

CSD TEMP PUSH FOR RISE ButtonWhen pushed, temperature rise (outlet temperature minusinlet temperature) is displayed on inner scale of CSDtemperature gages.

FLIGHT ENGINEER'S UPPER PANEL NO. 1

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AC BUS TIE ISOL Light (1, 2, 3) (Amber)Comes on when associated bus tie relay isopen.

AC BUS TIE ISOL Light (1, 2, 3) (Blue)Comes on when DUAL LAND mode isoperative and the associated bus tie relay isopen.

AC BUS OFF Light (1, 2, 3)Comes on when the associated AC bus isdeenergized. The ELEC cue and MASTERCAUTION lights also come on.

AC BUS TIE Switch (1, 2, 3)NORM Permits paralleled, unparalleled, or

isolated operation under automaticcontrol. Must be in NORM toprov ide e x t e r n a l power toassociated bus.

ISOL Insures isolation of the associatedgenerator bus.

EMER AC BUS OFF Light (L and R)Comes on when the associated emergency acbus is deenergized. The EMER BUS OFF sum-mary light (on pilot's overhead panel) and theMASTER WARNING lights also come on.

AC LOAD Meter (3)Indicates the load on the generator as com-pared to its rated load. Scale of .5 meansgenerator is operating at 50% of rated loadcapacity.


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ELECTRICAL SYSTEM - Controls & Indicators

DC X TIE SwitchOPEN - Switch is normally open to iso-

late the transformer/rectifiersby opening the dc x-tie RCCB.

CLOSE - Connects a deenergized dc busto an operative T/R through aselected, energized segment ofthe dc tie bus.

DC X TIE CLOSED LightComes on when the dc x-tie RCCB isclosed.

DC TIE Switch (1,3)OPEN - Switch is normally open to iso-

late the transformer/rectifiersby opening a dc tie relay.

CLOSE - Connects a deenergized dc busto an operative T/R through aselected, energized segment ofthe dc tie bus.

DC TIE CLOSED Light (1,3)Comes on when the associated dc tie relayis closed.

DC BUS OFF Light (1,2,3)Comes on when the associated dc bus is de-energized. The ELEC cue and MASTERCAUTION lights also come on.

EMER DC BUS OFF Light (L and R)Comes on when the associated emergencydc bus is deenergized. The EMER BUS OFFsummary light (on pilot's overhead panel)and the MASTER WARNING lights alsocome on.

DC LOAD Meter (4)Indicates transformer/rectifier output re-lative to its rating. Scale reading of .5 indi-cates unit is operating at 50% of rated out-put.


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DUAL LAND SELECTED LightComes on when DUAL LAND FGCS mode hasbeen selected. Indicates the main electricaldistribution system has been commanded tooperate in a manner appropriate to this typeof automatic landing.

DUAL LAND PWR ON LightComes on when DUAL LAND mode has beenselected and the electrical system configura-tion meets the requirements for this type ofautomatic landing.

BAT BUS OFF LightComes on when the battery bus is deenergiz-ed and the battery switch is in BAT position.Will come on momentarily when the BATswitch is moved to BAT and T/R output is noton battery bus.

BAT SwitchSwitch is shown in the on and locked (BAT)position. To turn OFF, the switch knob must berotated 90 counterclockwise (the symbolicline will now be vertical), pulled out to unlatchand moved downward to OFF.BAT Connects the battery to the battery

bus when the battery bus is notpowered from a normal source.Connects the battery to the batterycharger when the battery bus ispowered by a T/R and the ac groundservice bus is energized and the EMERPWR switch is OFF.

OFF Disconnects the battery from thebattery bus and the battery charger.External power can still be applied tothe main electrical system or the acground service bus.EXT PWR Switch

The magnetically-held EXT PWR position con-nects external power to the ac tie bus if theexternal power available light is on.

EXT PWR AVAIL Light (3)Comes on when external power of acceptablequality is connected to the main externalpower receptacle.

EXT PWR IN USE Light (2)F/E light comes on if external power availablelight is on and the external power switch is inthe EXT PWR position. The external power inuse light on the cabin ground service panelcomes on when the ground service relay(GSR) is closed to the external power by useof the associated switch.

(ONE ON CABIN GROUND SERVICE PANEL)

PARALLEL GENS ButtonWhen pushed, arms the automatic parallelingsystem. Subsequently, as individualgenerators attain the prescribed conditionsfor paralleling the auto parallel system willclose the corresponding BTR and connect theassociated generator bus to the ac tie bus.

Any set of conditions which would open a BTRwill disarm the automatic paralleling system.As a result, the system must be re-armed ifparalleling is desired. Paralleling cannot be ac-complished with external power on the ac tiebus, if any ac bus tie isolation switch is inISOL, if the APU generator is feeding a bus, orif any BTR trip signal is present.


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DC VOLT/AMP MeterDisplays selected dc bus 1, 2, or 3 voltages. InAPU GEN & START position, meter displaysAPU starter voltage and current. In the BAT &L EMER AC position of the VOLT/AMP/FREQselector, displays battery voltage and current.Charge readings on the ammeter indicate thatthe battery is being charged (the batteryswitch must be in BAT and the emergencypower switch must be in OFF). The dischargeside displays the load being drawn from thebattery. With the emergency power switch inON, the ammeter needle should indicatewithin the white discharge band. During APUstart, meter displays current (divided by 10)being drawn from the battery or the APU startTR depending upon the position of the APUSTART SEL switch.

GALLEY BUS Switch (1, 2, 3)ON Connects the galley bus to either

the associated ac generator bus orto galley external power.

OFF Disconnects the galley bus fromboth sources.

RESET-This momentary position willreinstate galley power if (a)automatic load shedding caused thepower to trip initially or, (b) thecause of the galley bus overload hasbeen corrected.

GLY EXT PWR SwitchGLYEXT PWR Energizes the galley buses if dc

power and galley external poweris available and the galley busswitches are ON. Switch ismagnetically held in the GLYEXT PWR position provided thatgalley external power isavailable.

OFF Removes galley external powerfrom the galley buses even withgalley external power con-nected.

GALLEY PWR OFF Light (3)Comes on if the galley is automatically dis-connected from the associated galley bus. Ifgalley power is disconnected by use of thegalley bus switch, the light will not come on.Three lights indicate a generator overload con-dition. One light indicates a disconnectedpower condition.

GALLEY EXT PWR IN USE LightComes on if GALLEY EXT PWR AVAIL light ison, the galley external power switch is in theGLY EXT PWR position, one or more galley busswitches are ON, and dc power is available.

GALLEY EXT PWR AVAIL Light (2)Comes on whenever ac external power ofacceptable quality is connected to the exter-nal galley receptacle.

(ONE ON MAIN EXT PWR PANEL)


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ELEC SYS RESET Switch (1,2,3)The switch is spring loaded to the center position. Aguard and a safety wire prevent inadvertent liftingof the switch to the BUS FAULT position. The mo-mentary BUS FAULT position will provide restora-tion of power to the faulted generator bus or the actie bus by releasing the lockout mechanisms of theassociated BTR and APR if the fault has beencleared. The momentary GEN RLY/BUS TIE RLYLOCKOUT position will clear a lockout of the asso-ciated GR and/or BTR relays. Movement toward thelatter position is not restrained by either guard orsafety wire.

GEN FAIL RESET ButtonA momentary pushbutton which will reset (turn off)the generator failure light if it is on due to a spurioussignal.

(UPPER MAIN CB PANEL)

AC VOLT MeterDisplays voltage of the ac power source as selectedby the VOLT/AMP/ FREQ selector. Normal and allow-able operating ranges are marked on the meter.

FREQ MeterDisplays frequency (Hz) of the ac power source selec-ted by the position of the VOLT/AMP/ FREQ selector.Normal and allowable operating ranges are markedon the meter.

VOLT/AMP/FREQ SelectorSelects power source to be displayed on amperes are displayed. If the emergencythe ac voltmeter, frequency meter and dc power switch is ON, the voltage and fre-volt/ammeter. When placed in either the quency of the inverter are displayed. In the1, 2, or 3 position, ac generator bus volt- APU GEN & START position, APU starterage, frequency, and debus voltage are dis- current and voltage, plus APU generatorplayed. In the BAT & L EMER AC position, ac voltage and frequency are displayed. Allac voltage and frequency of the left emer- other positions display only ac voltage andgency ac bus, plus battery voltage and frequency of the selected source.


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APU AC LOAD MeterIndicates the load on the generator as com-pared to its rated load. Reading of .5 meansthat APU generator is operating at 50% ofrated load.

APU GEN RESET SwitchIn APU GEN position, the APU generator con-trol (field) relay (GCR) is normally closed. Ifthe GCR is tripped by a protective circuit or bymanual operation of the APU fire controlswitch, the GCR can be closed by utilizing themomentary RESET position (provided the faulthas been cleared and the APU fire controlswitch is at NORM).

APU GEN OFF LightComes on during APU start (before generatoris up to speed) or whenever APU generatoroutput does not meet specified electrical re-quirements and the APU is up to speed. TheELEC cue and MASTER CAUTION lights willalso come on except during start sequence.Whenever the APU PWR AVAIL light is on, theAPU GEN OFF light will be off.

APU GEN FAIL LightComes on to indicate actual or impendingAPU generator failure or spurious signal. Toreset, a generator failure reset button, locatedon the Upper Mam CB Panel, may be pushed.If signal was spurious, generator failure lightwill go off.

APU PWR AVAIL Light (2)Comes on whenever APU generator isproviding power of correct phase rotation,voltage, and frequency.


APU GEN BUS Switch (1, 2, 3)ON Closes the associated auxiliary power

relay (APR) and puts the APU on thebus if the bus is not already poweredby the associated engine-drivengenerator. The APU has priority overexternal power.

OFF Disconnects APU from the generatorbus.

APU PWR IN USE Light (4)Comes on when APU PWR AVAIL light is ON,the APU GEN BUS switch is ON. and the elec-trical system mode has specified an APUpriority (APR is closed). The APU PWR IN USElight on the cabin ground service panel comeson when the APU generator supplies theground service bus thru the ground servicerelay (GSR).



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ADG Release Handle (Aft pedestal)Pulling aft and up breaks safety wire and deploysADG to produce three-phase power for 115 volts, 400Hz. ADG output (regulated by a constant-speedpropeller) is available at all airspeeds. Range loss due todeployment is about one percent. ADG electrical orhydraulic output is controlled by ADG switch. Oncedeployed, ADG cannot be stowed until on the ground.

ELEC Cue LightComes on whenever one or more of the following lightscome on: CSD OIL PRESS LO, GEN OFF, APU GEN OFF(except during normal start), AC BUS OFF, and DC BUSOFF. MASTER CAUTION lights also come on.

EMER BUS OFF Summary LightComes on whenever one or more of following lightscome on: L EMER AC BUS OFF, R EMER AC BUS OFF, LEMER DC BUS OFF, and R EMER DC BUS OFF.MASTER WARNING lights also come on.

EMER PWR SwitchOFF - Permits left emergency ac and dc buses to

receive power from main distribution systemand battery to be charged (if battery switch is inBAT).

ON - Left emergency ac and dc buses are transferredto inverter and battery respectively. ON turns onEMER PWR IN USE lights and disconnectsbattery charger from battery.

(ONE ON F/E UPPER PANEL NO. 1)

EMER PWR IN USE Light (2)Comes on when emergency power switch is moved toON. Indicates that essential equipment is connected toemergency power source.

ADG SwitchR EMERELEC - With ADG deployed ADG bus powers right

emergency ac bus and, through associatedT/R 3, right emergency dc bus.

HYD - Normal inflight position. With ADG deployed,connects ADG bus to auxiliary hydraulic pump 1.

OVERHEAD PANEL

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DC GND SERVICE BUS OFF LightComes on when dc ground servicebus is deenergized.

(FLIGHT ENGINEER'S UPPER PANEL NO. 2)

DC GND SERVICE BUS PWR SwitchNormally in the NORM (switch guardclosed) position.ALTN Connects dc ground ser-

vice bus to alternatepower source (T/R 2A).DC GND SERVICE BUSOFF light should go off.

NORM Connects dc ground ser-vice bus to normal powersource (T/R 2B).

FLIGHT ENGINEER'S EQUIPMENT PANEL

Effective on airplanes with DC Ground Service Bus AlternatePower Source (SB 24-90 incorporated or Production Equivalent).JL

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ELECTRICAL SYSTEM

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ELECTRICAL SYSTEM

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ELECTRICAL SYSTEM

Effective for aircraft with DC Ground Service BusAlternate Power Source.

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ELECTRICAL SYSTEM

in 1/96 06-40-07/08

McDonnell Douglas DC 10 40 Electrical

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