ELECTRICAL POWER - DESCRIPTION AND OPERATION

** ON A/C NOT FOR ALL

1. General

Electrical Power - General Schematic ** ON A/C NOT FOR ALL

A. Generation
Two Integrated Drive Generators (IDG) normally supply the aircraft electrical power in flight ; each engine drives one generator.
The APU drives a third, auxiliary, generator (APU GEN) which can replace either main generator (GEN 1 or GEN 2).
The generators supply the distribution network with alternating current.
Two Transformer Rectifiers (TR) supply, in normal configuration, the distribution network with direct current. In the event of major failure, a constant-speed hydraulic motor drives an emergency generator (CSM/G) to supply the systems required for aircraft control.
On the ground, an electrical Ground Power Unit (GPU) can supply the aircraft. The APU GEN can also be an independant power source.

B. General Arrangement of the Distribution Network
In normal flight configuration, each IDG supplies its own distribution network via its Line Contactor (GLC). The two IDGs are never electrically coupled.
The distribution network 1 consists of:

the Alternating Current Bus 1 (AC BUS 1),
the Alternating Current Essential Bus (AC ESS BUS),
the Alternating Current Sheddable Essential Bus (AC SHED ESS BUS).

The distribution network 2 corresponds to the Alternating Current Bus 2 (AC BUS 2).
The TR 1 powered from the AC BUS 1 supplies through its contactor:

the Direct Current Bus 1 (DC BUS 1),
the Direct Current Battery Bus (DC BAT BUS),
the Direct Current Essential Bus (DC ESS BUS),
the Direct Current Sheddable Essential Bus (DC SHED ESS BUS).

Two batteries are associated with the DC BAT BUS.
The TR 2 powered from the AC BUS 2 supplies the Direct Current Bus 2 (DC BUS 2) through its contactor.
In case of loss of the TR 1 or the TR 2, a third Essential Transformer Rectifier (ESS TR) powered from the AC BUS 1, supplies through its contactor:

the DC ESS BUS,
the DC SHED ESS BUS.

In certain failure configurations, the AC ESS BUS and the AC SHED ESS BUS plus, via the ESS TR, the DC ESS BUS and the DC SHED ESS BUS can be supplied by:

the AC BUS 2 if the AC BUS 1 is lost,
the CSM/G more especially in emergency configuration or smoke emergency configuration.

Two sheddable AC and DC busbars are powered respectively by the GLC 2 and the TR 2 and controlled by two contactors. These AC busbars are automatically shedded in the single generator configuration and the DC busbars in the single generator and single TR configurations.

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2. Component Location

A. Main Component Location

Electrical Power - Component Location ** ON A/C NOT FOR ALL

Control and Indicating - Component Location ** ON A/C NOT FOR ALL

Electrical Power - Component Location ** ON A/C NOT FOR ALL

Control and Indicating - Component Location ** ON A/C NOT FOR ALL

FIN	FUNCTIONAL DESIGNATION	PANEL	ZONE	ATA REF
** ON A/C ALL
1PE	TR-ESS		125	24-34-51
3XB	STAT INV		126	24-28-51
1XE	CONTROL UNIT-CSM/G		125	24-24-34
8XE	CSM/G		148	24-24-51
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1XG	GPCU	92VU	122	24-41-34
** ON A/C NOT FOR ALL
1XG	GPCU	92VU	121	24-41-34
** ON A/C ALL
20XG	RCPT-EXT PWR	121AL	120	24-41-51
** ON A/C NOT FOR ALL
1XS	GCU-APU	91VU	121	24-23-34
** ON A/C NOT FOR ALL
8XS	GEN-APU		310	24-23-51
** ON A/C NOT FOR ALL
8XS	GEN-APU		316	24-23-51
** ON A/C ALL
1XU1	GCU-1	91VU	121	24-22-34
1XU2	GCU-2	91VU	121	24-22-34
** ON A/C NOT FOR ALL
22XU1	EGIU-1	95VU	121	24-22-33
22XU2	EGIU-2	96VU	122	24-22-33
** ON A/C ALL
4000XU	IDG		435	24-21-51
** ON A/C NOT FOR ALL
24XG	GAPCU	92VU	122	24-41-34

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3. System Description

A. AC Generation and Distribution

AC Generation and Distribution - Schematic ** ON A/C NOT FOR ALL

(1) Generation

(a) Main generator and APU GEN drive:

Each main generator is driven by an engine HP compressor via an accessory gearbox and an integrated hydromechanical speed regulator which transforms the engine variable speed into constant speed for the generator.
In the event of mechanical failure, the IDG pushbutton switch protected by a guard and located on the ELEC panel on the overhead panel, serves to disconnect the IDG.
The disconnection mechanism can be reset on the ground only with the engine shut down.
The APU directly drives the APU GEN at constant speed. This maintains the generator frequency constant.

(b) Main Generator, APU GEN and Generator Control Unit (GCU)
Each generator is controlled, via a GCU, by a GEN pushbutton switch located on the ELEC panel on the overhead panel.
The leading particulars of the generator are:

nominal power: 90 KVA at the POR,
voltage: 115 V/200 V, three-phase, 400 Hz.

The main functions of the GCU are:

to regulate the generator voltage by the field current,
to protect the network and the generator by control of the associated GLC and the generator field current,
to provide BITE information to the Ground Power Control Unit (GPCU),
to control the warnings associated with the corresponding channel.

Each GCU includes a BITE and self monitoring system which:

analyzes most of the faults that affect the channel,
memorizes the corresponding data in a non-volatile memory.

In addition the lower ECAM display unit receives the electrical parameters and warnings dealing with the channel concerned.
This data transmission is effected via the Electrical Generation Interface Unit (EGIU).

(c) Electrical Generation Interface Unit (EGIU)
The main function of the EGIU is to process the parameters from the GCU and associated generator. The EGIU then transmits the information to the cockpit (ECAM) via the System Data Acquisition Concentrators (SDACs).
Two EGIUs are installed on the aircraft.
One EGIU is associated with the GCU1 and the GPCU.
This EGIU receives parameters in analog and discrete form:

GEN1 on channel 1 and,
external power on channel 2.

Each channel sends its own parameters to SDAC1 and SDAC2 through two isolated ARINC 429 data links.
The second EGIU is connected in the same manner to generator 2 and to the APU generator.

(d) CSM/G drive
In emergency conditions, a hydraulic motor speed-controlled by a servo-valve speed regulator drives the CSM/G. The regulator uses the oil flow from the Blue Hydraulic system to maintain the CSM/G at a constant speed.
In normal conditions, an electric pump supplies the Blue hydraulic system. In emergency conditions, the Ram Air Turbine (RAT) supplies the Blue system.

(e) CSM/G and CSM/G control unit
Loss of the AC BUS 1 and AC BUS 2 automatically controls the RAT and the CSM/G.
The MAN ON guarded pushbutton switch located on the EMER ELEC PWR panel on the cockpit overhead panel serves to manually control the RAT and the CSM/G. This control is redundant with the automatic RAT deployment logic.
The CSM/G control unit enables full control of the CSM/G.
The leading particulars are :

Nominal Power : 5KVA at POR
Voltage : 115/200VAC, three-phase, 400 Hz.

The main functions of the control unit are :

to control the servo-valve excitation for speed regulation
to control the generator voltage by regulation of the field current
to protect the network and the generator by control of the associated GLC and the generator field current
to limit the power delivered at low aircraft speed by limitation of the field current (with respect to the RAT characteristics).

The EMER GEN TEST guarded pushbutton switch on the EMER ELEC PWR panel allows to test the CSM/G on the ground, with the Blue electric pump running.

(f) Static inverter
The static inverter of 350 VA nominal power transforms the direct current voltage from the BAT BUS into a single phase, 115V 400Hz, alternating current.
The static inverter is automatically activated in the event of loss of the AC BUS 1 and AC BUS 2.
For maintenance purposes, the static inverter delivers FAULT indication to the centralized fault display system (CFDS) through the two battery charge limiters (BCL), (Ref. Para. 3. A. (2)).

(2) Generation

(a) Main Generator, APU GEN, Generator Control Unit (GCU) and Ground and Auxiliary Power Control Unit (GAPCU).
Each generator is controlled, via a GCU and via the GAPCU for the APU generator, by a GEN pushbutton switch located on the ELEC panel on the overhead panel.
The leading particulars of the generator are:

nominal power: 90 KVA at the POR,
voltage: 115 V/200 V, three-phase, 400 Hz.

The main functions of the GCU and GAPCU are:

to regulate the generator voltage by the field current,
to protect the network and the generator by control of the associated GLC and the generator field current,
to provide BITE information to the Centralized Fault Display System (CFDS),
to control the warnings associated with the corresponding channel.

Each GCU and the GAPCU include a BITE and self monitoring system which:

analyzes most of the faults that affect the channel,
memorizes the corresponding data in a non-volatile memory.

In addition the lower ECAM display unit receives the electrical parameters and warnings dealing with the channel concerned.

(b) CSM/G drive
In emergency conditions, a hydraulic motor speed-controlled by a servo-valve speed regulator drives the CSM/G. The regulator uses the oil flow from the Blue Hydraulic system to maintain the CSM/G at a constant speed.
In normal conditions, an electric pump supplies the Blue hydraulic system. In emergency conditions, the Ram Air Turbine (RAT) supplies the Blue system.

(c) CSM/G and CSM/G control unit
Loss of the AC BUS 1 and AC BUS 2 automatically controls the RAT and the CSM/G.
The MAN ON guarded pushbutton switch located on the EMER ELEC PWR panel on the cockpit overhead panel serves to manually control the RAT and the CSM/G. This control is redundant with the automatic RAT deployment.
The CSM/G control unit enables full control of the CSM/G.
The leading particulars of the CSM/G are:

Nominal Power: 5 KVA at POR
Voltage: 115/200 VAC, three-phase, 400 Hz.

The main functions of the control unit are:

to control the servo-valve excitation for speed regulation,
to regulate the generator voltage by the field current,
to protect the network and the generator by control of the associated GLC and the generator field current.

The EMER GEN TEST guarded pushbutton switch on the EMER ELEC PWR panel allows to test the CSM/G on the ground, with the Blue electric pump running.

(d) Static inverter
The static inverter, with a 1000 VA nominal power, transforms the direct current from the battery 1 into a single phase, 115 V 400 Hz, alternating current.
The static inverter is automatically activated if AC BUS 1 and AC BUS 2 are lost and the CSM/G is unavailable.
For maintenance purposes, the static inverter delivers FAULT indication to the Centralized Fault Display System (CFDS) through the two Battery Charge Limiters (BCL).

(3) Generation

(a) Main Generator, APU GEN, Generator Control Unit (GCU) and Ground and Auxiliary Power Control Unit (GAPCU)
Each generator is controlled, through the GCU and the GAPCU for the APU generator, with a GEN pushbutton switch installed on the ELEC panel on the overhead panel.
The primary properties of the generator are:

Nominal power: 90 kVA at the Point Of Regulation (POR)
Voltage: three-phase 115/200VAC, 400 Hz.

The primary functions of the GCU and GAPCU are:

Control of the generator voltage through the field current
Protection of the network and the generator through the control of the related GLC and the generator field current
Supply of BITE information to the Centralized Fault Display System (CFDS)
Control of the warnings related to the applicable channel.

Each GCU and the GAPCU have a BITE and self-monitoring system that:

Analyzes most channel faults
Memorizes the related data in a non-volatile memory.

Also, the lower ECAM display-unit receives the electrical parameters and warnings for the related channel.

(b) Constant Speed Motor/Generator (CSM/G) drive
In emergency conditions, a hydraulic motor, speed-controlled by a servo-valve speed regulator, operates the CSM/G. The regulator uses the oil flow from the Blue hydraulic system to keep the CSM/G at a constant speed.
In normal conditions, an electric pump supplies the Blue hydraulic system. In emergency conditions, the Ram Air Turbine (RAT) supplies the Blue hydraulic system.

(c) CSM/G and CSM/G control unit
In emergency conditions, the loss of busbars AC BUS 1 and AC BUS 2 starts the automatic control of the RAT and CSM/G.
The guarded MAN ON pushbutton switch, on the EMER ELEC PWR panel of the cockpit overhead panel, is used to manually control the RAT and the CSM/G. This control is redundant with the automatic RAT deployment.
The CSM/G control unit controls the CSM/G.
The primary properties of the CSM/G are:

Nominal power: 5.4 kVA at the POR
Voltage: three-phase 115/200VAC, 400 Hz.

The primary functions of the control unit are:

Control of the servo-valve excitation for speed regulation
Control of the generator voltage through the field current
Protection of the network and the generator through the control of the related GLC and generator field current.

The guarded EMER GEN TEST pushbutton-switch on the EMER ELEC PWR panel is used to do a test of the CSM/G on the ground, with the Blue electric pump in operation.

(d) Static inverter
The static inverter, has a nominal power of 1000 VA. It changes the direct current from battery 1 into single-phase 115VAC/400 Hz.
The static inverter is automatically activated if busbars AC BUS 1 and AC BUS 2 are lost and the CSM/G is not available.
For the maintenance, the static inverter supplies FAULT indications to the CFDS through the two Battery Charge Limiters (BCLs).

(4) Transfer Circuit
The transfer circuit enables supply of either AC electrical network or both from one of the four power sources (GEN 1, GEN 2, APU GEN, EXT PWR) via the Bus Transfer Contactors (BTC). BTC control is entirely automatic and depends on the availability of these sources and the correct condition of each network. The BTC 1 closes, if no interlock condition exists on the GCU 1:

when the GEN 1 is not available, in order to supply the network 1 from another power source (GEN 2 APU GEN or EXT PWR),
to supply the network 2 from the GEN 1, if the GEN 2, APU GEN and EXT PWR are not available.

The BTC 2 control is symmetrical to BTC 1.
The GCU 1 or GCU 2 enables closure of the BTC 1 or BTC 2 if no undervoltage condition and no "GLC welded" failure occurred (Ref. AMM D/O 24-22-00-00).
The networks 1 and 2 are supplied in priority order:

by the corresponding generator,
by the ground power unit,
by the APU GEN,
or by the other generator.

NOTE: Locking of the two BTCs and isolation of the two channels is possible by action on the BUS TIE pushbutton switch; this control is located on the ELEC panel on the cockpit overhead panel.

(5) Transfer Circuit
The transfer circuit enables supply of either AC electrical network or both from one of the four power sources (GEN 1, GEN 2, APU GEN, EXT PWR) via the Bus Transfer Contactors (BTC). BTC control is entirely automatic and depends on the availability of these sources and the correct condition of each network. The BTC 1 closes, if no interlock condition exists on the GCU 1:

when the GEN 1 is not available, in order to supply the network 1 from another power source (GEN 2 APU GEN or EXT PWR),
to supply the network 2 from the GEN 1, if the GEN 2, APU GEN and EXT PWR are not available.

The BTC 2 control is symmetrical to BTC 1.
The GCU 1 or GCU 2 enables closure of the BTC 1 or BTC 2 if no overcurrent condition and no "GLC welded" failure occurred (Ref. AMM D/O 24-22-00-00).
The networks 1 and 2 are supplied in priority order:

by the corresponding generator,
by the ground power unit,
by the APU GEN,
or by the other generator.

NOTE: Locking of the two BTCs and isolation of the two channels is possible by action on the BUS TIE pushbutton switch; this control is located on the ELEC panel on the cockpit overhead panel.

(6) Distribution
The alternating current distribution network comprises three independent parts.
The network 1 mainly comprises the AC BUS 1, the AC ESS BUS and the AC SHED ESS BUS which are three-phase, 115 V/400 Hz busses.
The AC BUS 1 supplies the essential busses in series.
The AC BUS 1 and the AC ESS BUS also deliver 26 V/400 Hz power supply through their 115/26 V transformer.
In the event of AC BUS 1 loss, AC ESS BUS and the AC SHED ESS BUS can be manually restored by the transfer of power supply directly from the AC BUS 2. It is possible to perform the transfer by action on the AC ESS FEED pushbutton switch on the ELEC panel, after illumination of the FAULT legend.
In the event of AC BUS 1 and AC BUS 2 loss (emergency configuration), the AC ESS BUS and AC SHED ESS BUS are restored on the CSM/G when the RAT hydraulic power is available.
During RAT deployment or when the following two conditions are both met:

main landing gear compressed,
and A/C speed below 100 Knots,

AC ESS BUS and AC STAT INV BUS are supplied by battery 1 via the static inverter.
The network 2 includes the AC BUS 2 which is a three-phase, 115 VAC/400 Hz bus.
It also delivers 26 VAC/400 Hz power supply through a 115/26 VAC transformer.

NOTE: To carry out ground service operations (Ref. Para. C.), the external power receptacle provides independent and direct supply to a part of the network 2.

B. DC Generation and Distribution

DC Generation and Distribution - Schematic

(1) DC Power Sources
The power sources of direct current are:

three identical transformer rectifiers and two identical batteries.

In normal configuration, the two normal TRs (TR 1 and TR 2) and possibly the batteries supply direct current.
In the event of loss of one or both TR, part of the DC network is transferred to the ESS TR.

(a) TR
Each TR transforms the three-phase alternating current into direct current (28VDC).

1 TR1 and TR2
Upon energization, the two normal TRs operate and supply the DC network via a contactor controlled by the internal TR logic.
In case of failure, the TR sends a FAULT signal to the CFDS for maintenance purposes.

2 Essential TR
Upon energization, the essential TR operates and supplies the DC network via a contactor. To reset the TR push the TR RST pushbutton switch 15PU located on the relay box 103VU.In addition,the TR sends its electrical parameters to the lower ECAM display unit. In addition, the TR sends its electrical parameters to the lower ECAM display unit.

(b) Batteries
Each of the two batteries has a nominal 23 AH capacity and a 24 VDC voltage. The main functions of the batteries are:

to start the APU in flight and on the ground,
to supply the essential network in some configurations.

A BCL controls each battery contactor when the BAT pushbutton switch is in the AUTO configuration.
In addition, each BCL includes a BITE and a self monitoring system which analyzes internal and peripherical fault information. Initiation of the test is possible via the CFDS or at each power up on ground.
Each BCL delivers electrical parameters and warnings concerning each battery to the lower ECAM display unit.

(2) Distribution
The direct current distribution network is divided into two parts.
The network 1 comprises the DC BUS 1, the DC BAT BUS, the DC ESS BUS and the DC SHED ESS BUS. The TR 1 supplies the network 1.
The network 2 comprises the DC BUS 2. The TR 2 supplies the network 2.
In the event of TR 1 loss, the TR 2 automatically restores supply to the DC BUS 1 and the DC BAT BUS. The DC ESS BUS and the DC SHED ESS BUS are automatically transferred to the ESS TR.
The AC BUS 1 supplies the ESS TR.
The TR 2 loss leads to the symmetrical recovery of the DC BUS 2 from the TR 1 and the same transfer for the DC ESS BUS and the DC SHED ESS BUS.
In the event of TR 1 and TR 2 loss (DC BUS 1 and 2 loss), the DC ESS BUS and the DC SHED ESS BUS are supplied from the ESS TR.
In case of loss of AC BUS 1 and AC BUS 2 (emergency configuration), DC ESS BUS and DC SHED ESS BUS are recovered by the CSM/G (via the ESS TR) when the RAT hydraulic generation is available.
During RAT deployment or when the following two conditions are both met:

main landing gear compressed,
and A/C speed below 100 Knots,

DC ESS BUS only is supplied by battery 2.

NOTE: The external power receptacle directly energizes the TR 2 which can independently supply a part of the DC normal network. (Ground service configuration).

C. Power Supply Via the External Power Receptacle

AC Generation and Distribution - Schematic ** ON A/C NOT FOR ALL

(1) AC External Power Control Supply
An external power receptacle located in front of the nose landing gear well enables power supply of the aircraft network. This is performed by means of the three-phase, 400 Hz, 115/200 V ground power unit.
External power supply is controlled from the ELEC panel on the cockpit overhead panel and via the GPCU.
The GPCU includes a BITE and a self monitoring system which analyzes most of the faults which may affect the channel. The system memorizes the corresponding information in a non-volatile memory.
This memory also memorizes the fault information from each main GCU.
Finally, the GPCU delivers all fault information to the CFDS.
The test is initialized:

either on the ground by the CFDS,
or automatically at each power-up.

Each main GCU or APU GEN GCU then receives the test request.
In addition, the GPCU delivers electrical parameters relative to its channel to the EGIU 1, channel 2.

(2) AC External Power Control Supply
An external power receptacle located in front of the nose landing gear well enables power supply of the aircraft network. This is performed by means of the three-phase, 400 Hz, 115/200 V ground power unit.
External power supply is controlled from the ELEC panel on the cockpit overhead panel and via the GAPCU.
The GAPCU includes a BITE and a self monitoring system which analyzes most of the faults which may affect the channel. The system memorizes the corresponding information in a non-volatile memory.
This memory also memorizes the fault information from each main GCU.
Finally, the GAPCU delivers all fault information to the CFDS.
The test is initialized:

either on the ground by the CFDS,
or automatically at each power-up.

In addition, the GPCU delivers electrical parameters relative to its channel to the EGIU 1, channel 2.

(3) Ground Service Bus Control

Control and Indicating - Component Location ** ON A/C NOT FOR ALL

It is possible to supply a part of the aircraft electrical network as follows, directly from the external power receptacle, to carry out ground service operations :

supply of part of the AC network (AC SVCE busses),
supply of part of the DC network (DC SVCE busses), without energization of the whole aircraft electrical network.

The MAINT BUS switch located on the panel 2000VU controls the supply of the ground service network.

** ON A/C NOT FOR ALL

4. Controls and Indications Related to Electrical Generation and Distribution

Control and Indicating - Component Location ** ON A/C NOT FOR ALL

Controls and indications related to electrical generation and distribution are on:

the ELEC control panels,
the ECAM display units,
the forward entryway circuit breaker panel (2000VU),
the CFDS.

A. MAINT BUS Switch

Control and Indicating - Component Location ** ON A/C NOT FOR ALL

This switch is located on the panel 2000VU. It controls power supply of the AC and DC ground/flight network.
ON: This network is supplied in priority as follows:

by the aircraft network if it is energized,
or by the electrical ground power unit, via the external power receptacle.

OFF: This network is supplied by the main electrical network.

B. Central Warning System

Lower ECAM Display Unit - ELEC Page

The block diagram of the electrical generation appears on the lower ECAM display unit (Ref. AMM D/O 24-27-00-00).

C. Centralized Fault Display System (CFDS)
Line maintenance of the electronic systems is based on the use of the CFDS.
The purpose of the CFDS is to give to maintenance technicians a central maintenance aid. The CFDS enables intervention at system or subsystem level from the Multipurpose Control and Display Units (MCDUs) located in the cockpit.
From the MCDUs it is possible:

to read the maintenance information,
to initiate various tests.

The electrical components connected to the CFDS are:

the GPCU,
the BCLs,
the emergency GCU,
the TRs.

The GPCU and BCLs can memorize fault codes and communicate with the CFDIU via ARINC 429 buses.
The emergency GCU and the three TRs are connected to the CFDIU by a discrete link: it is thus possible to know only the status of these systems (OK or faulty) during SYSTEM REPORT/TEST sequence.

NOTE: The GCU1, the GCU2 and the APU GCU are continuously monitored by the GPCU.
The GPCU can then transmit to the CFDIU all the failure messages corresponding to the failure codes recorded by these GCUs and the GPCU.

Line maintenance of the electronic systems is based on the use of the CFDS.
The purpose of the CFDS is to give to maintenance technicians a central maintenance aid. The CFDS enables intervention at system or subsystem level from the Multipurpose Control and Display Units (MCDUs) located in the cockpit.
From the MCDUs it is possible:

to read the maintenance information,
to initiate various tests.

The electrical components connected to the CFDS are:

the GAPCU,
the BCLs,
the emergency GCU,
the TRs.

The GAPCU and BCLs can memorize fault codes and communicate with the CFDIU via ARINC 429 buses.
The emergency GCU and the three TRs are connected to the CFDIU by a discrete link: it is thus possible to know only the status of these systems (OK or faulty) during SYSTEM REPORT/TEST sequence.

[Rev.10 from 2021] 2026.04.01 04:51:44 UTC