INTEGRATED DRIVE GENERATOR SYSTEM (IDG, GCU) - DESCRIPTION AND OPERATION

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1. General

Diagram ** ON A/C NOT FOR ALL

Each engine (HP rotor) controls its related Integrated Drive Generator (IDG) through the accessory gearbox.
The drive speed changes in relation to the engine rating.
The IDG supplies 115/200 VAC, 3-phase, 400 Hz power to the engine and aircraft, at the Point of Regulation (POR).
The IDG has two parts:

The drive with the Constant Speed Drive (CSD) and,
The generator.

The hydromechanical CSD with its servo-valve operate the AC generator at constant speed.

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2. Component Location

A. IDG System Control

IDG System Control - Component Location ** ON A/C NOT FOR ALL

Generator System ** ON A/C NOT FOR ALL

FIN	FUNCTIONAL DESIGNATION	PANEL	ZONE	ATA REF
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5XT	P/BSW-ELEC/IDG 1	35VU	210	24-21-00
6XT	P/BSW-ELEC/IDG 2	35VU	210	24-21-00
4000XU1	IDG-ENG 1		435	24-21-00
4000XU2	IDG-ENG 2		445	24-21-00
1XM1	ADAPTER-QUICK ATTACH/DETACH (QAD), ENG 1 IDG		440	24-20-00
1XM2	ADAPTER-QUICK ATTACH/DETACH (QAD), ENG 2 IDG		440	24-20-00
5001XM1	IDG1 FUEL/OIL HEAT EXCHANGER		453	24-21-42
5001XM2	IDG2 FUEL/OIL HEAT EXCHANGER		463	24-21-42
5002XM1	IDG1 OIL/OIL HEAT EXCHANGER		453	24-21-42
5002XM2	IDG2 OIL/OIL HEAT EXCHANGER		463	24-21-42
9XT	SENSOR-DIFF PRESS, IDG FUEL/OIL HEAT		400	24-21-00

(1) The IDG is installed on the rear left side of the engine main gearbox.

(2) The IDG Quick-Attach-Detach (QAD) adapter is installed on the IDG mounting pad on the rear left side of the main gearbox.

(3) The IDG power-cable disconnect-block is attached to the IDG housing at the ten o'clock position.

(4) The IDG power cables are connected, at one end, to the lower IDG power-cable disconnect-block attached to the IDG. The other end of the IDG power cables is connected to the upper IDG power-cable disconnect-block installed on the left pylon above the diffuser case.

(5) The IDG fuel/oil heat-exchanger is installed at the 9 o'clock position on the High Pressure Turbine (HPT) case.

(6) The IDG fuel/oil heat-exchanger pressure-sensor is installed below the IDG fuel/exchanger.

(7) The IDG oil/oil heat-exchanger is at the 9 o'clock position on the diffuser case.

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3. System Description

A. IDG and Generator Control Unit (GCU)

(1) In flight, the IDG supplies AC power (115 VAC/400 Hz) to the aircraft with its two units:

The CSD unit
The generator.

The engine-driven CSD unit changes the input speed (XX - XX rpm) from the main gearbox into a constant rotational speed of 24000 rpm.
The constant 24000 rpm speed from the CSD unit is transmitted to the generator which supplies AC power (115 VAC/400 Hz) to the aircraft.

(2) The GCU, installed in the maintenance equipment center, is used to control the voltage and frequency. It is also used to prevent the electric-power generation channel from the overcurrent. The GCU receives an input speed signal from the IDG speed sensor.

(a) Each GCU controls its related IDG:

GCU1 controls IDG1.
GCU2 controls IDG2.

(b) The primary functions of the IDG regulation and protection are:

The regulation of the generator voltage at the POR
The regulation of the generator speed
The monitoring and protection of the system.

(3) The IDG oil-cooling system lubricates the IDG and decreases its temperature. The system controls the IDG oil temperature with a heat movement between the IDG oil, the engine oil, and the engine fuel. The IDG oil-cooling system operates independently from the engine oil system.

(a) The IDG oil-cooling system is a passive system. It has two sections:

An oil/oil heat-exchanger
A fuel/oil heat-exchanger.

The oil flows out of the IDG to the core of the oil/oil heat exchanger where the heat from the IDG oil is transmitted to the engine oil. This usually occurs in hot conditions when the engine is at idle and the generator oil system is hotter than the engine oil system.

(4) In normal conditions, the heat is transmitted to the IDG oil from the engine oil. Then, the oil flows downstream to the IDG fuel/oil cooler to decrease the temperature of the IDG.
An IDG fuel/oil-cooler bypass-valve keeps the IDG oil temperature to a minimum.
To keep the IDG-oil maximum temperature, the IDG oil flows continuously through the fuel/oil heat exchanger.

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4. Power Supply

A. Circuit Breaker Table

PANEL	DESIGNATION	FIN	LOCATION
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122VU	ELEC/IDG1/DISC	1XT	T24
122VU	ELEC/IDG2/DISC	2XT	T25

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5. Interface

A. Generator Control Unit

(1) Input data

Each GCU receives the signals that follow from its related IDG:

Oil inlet temperature
Oil outlet temperature
Low oil pressure
Clogged filter indication
PMG 3-phase output voltage
CT 3-phase signal.

(2) Output data

Each GCU supplies the output analog data that follow to the System Data Analog Converter (SDACs), through the an ARINC 429 link:

IDG oil-output temperature
IDG oil-inlet temperature
AC load at the POR
AC frequency (phase A)
AC voltage (phase A) at the POR.

It also supplies the SDACs with the discrete information that follows through an ARINC 429 link:

Overload warning
Generator fault
IDG disconnect status
IDG-disconnect pushbutton position
IDG oil-outlet overheat
IDG-oil low pressure
GEN pushbutton-switch position
Clogged filter information
Low oil-level indication
IDG oil-outlet temperature-advisory.

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6. Component Description

A. IDG

IDG ** ON A/C NOT FOR ALL

Oil Cooling System of the IDG ** ON A/C NOT FOR ALL

Connectors, Port and Accessory Locations of the IDG ** ON A/C NOT FOR ALL

Internal Equipment of the Oil System ** ON A/C NOT FOR ALL

Internal Electrical Schematic of the IDG ** ON A/C NOT FOR ALL

(1) The IDG has the components that follow:

(a) Electrical circuit

Terminal block with a terminal block cover
Electrical connectors A, B and C.

(b) Maintenance components

Oil replenishing circuit
Oil drainage circuit
Oil level sight-glass
Oil scavenge filter-element
Oil charge filter-element
Vent valve
IDG reset ring.

Clogging indicator of the oil scavenge filter on the IDG oil-out line.

(d) Cooling system

Oil-in port
Oil-out port.

(2) The IDG has a CSD unit and a generator installed in a magnesium-cast housing.

(a) The speed conversion components are the gear differential and the hydraulic trim unit. The engine gearbox supplies the variable-speed shaft power to the IDG input shaft, which is directly connected to the carrier shaft of the differential.

(3) The IDG CSD unit has a disconnect mechanism to disengage the input shaft attached to the main gearbox. The disconnection is necessary to prevent internal mechanical damage if a failure of the IDG oil-cooling system occurs.

(4) IDG servo valve

(a) Generator speed control

A system with a servo valve in the IDG and an electronic control circuit in the GCU control the generator speed.
This system sets the position of the wobbler of the variable displacement hydraulic-unit.

(b) Electronic control circuit

The electronic control circuit monitors the generator PMG frequency and compares it with a reference source.
If there is an error signal, the control circuit causes the servo valve to increase or decrease the control piston pressure as necessary to set the generator frequency back to 400 Hz.

(5) The IDG has the components that follow:

(a) Internal components connected to connector A

The PMG stator
Three current transformers
Disconnect solenoid
The charge pressure switch.

(b) Internal components connected to connector B

The main exciter
The oil-in and oil-out temperature bulbs
The oil level sensor
The clogged filter indicator.

The servo valve.

(6) The IDG drive splines are lubricated by the engine oil-cooling system, which supplies a stream of oil to the center of the shaft. Oil from the shaft goes through the splines and is released into the gearbox cavity through radial holes in the shaft.

(7) IDG cooling and lubrication system

The oil goes into the IDG at the opposite side of the drive end through the DPI filter and then goes to:
The differential gear
The input seal
The charge pump
The generator stator and rotor.
The oil supplied to the differential gear also cools the PMG stator by spraying and lubricates the disconnect spline. The input housing has rectangular grooves around the main generator stator core in which oil flows to cool the stator and keep a low IDG surface temperature.
The charge pump draws in the oil flow at its suction port and increases its pressure.
The oil that goes into the rotor cools the components that follow:
The exciter and main generator rotors
The exciter and main generator windings
The diodes.

Then, this oil goes directly to the deaerator or to the IDG sump where it is scavenged and pumped to the deaerator.
The oil is deaerated and before it goes to the supply pump. There it runs through the scavenge filter into the external system lines for cooling.

(8) IDG sensors and protective components

(a) IDG oil filter Differential Pressure Indicator (DPI)

The scavenge filter has an oil filter DPI. The indicator shows when it is necessary to replace the oil filter elements.
The sensing device for the oil filter DPI is automatically inhibited during cold oil-running conditions. This prevents unwanted operation because of a high oil viscosity.
It is necessary to replace the two filters elements when the DPI is extended.

(b) IDG automatic and manual thermal disconnect-mechanism

1 The manual disconnect mechanism has a solenoid, a spring-loaded disconnect plunger, a cam shaft and a reset ring. The crew pushes the IDG pushbutton switch when the IDG FAULT legend comes on. When activated, the IDG cannot be connected again in flight.

2 At an IDG oil temperature of 199 deg.C (390.2 deg.F), an automatic thermal disconnect-mechanism disconnects the IDG.

The switch is usually closed when the IDG is stop and open when the IDG operates correctly.
The charge switch operates when the engine is at the normal operating speed. When the IDG charge pressure decreases to a minimum safe value, it transmits a signal to the GCU. The IDG FAULT legend comes on the ELEC panel. At the same time, the IDG LOW OIL PR caution message is shown on the upper Electronic Centralized Aircraft Monitoring (ECAM) Display Unit (DU).

(d) Clogged-filter indicator

The clogged filter indicator is in the IDG scavenge oil system. If the scavenge filter is clogged, the indicator will send a ground signal to the GCU.

The GCU transmits a status signal to the ECAM system. The ECAM generates an IDG MINOR FAULT warning with a related IDG CLOGGED FILTER message through the Centralized Maintenance System (CMS).

(e) Remote Oil Level Sensor (ROLS)

The ROLS uses a thermal dispersion method to monitor the IDG oil level and find if a sensor is wet or dry. If a sensor is dry, an "ELEC IDG 1 (2) OIL LO LVL" ECAM warning is shown on the upper ECAM DU with a related "LOW OIL LEVEL/IDG1 (2) (E1 (2)-4000XU)" message through the CMS.

(f) IDG oil-out and oil-in temperature sensor

The oil-out and oil-in temperature sensors of the IDG are sensed by the GCU to do the ECAM oil-out temperature and delta (oil-out minus oil-in) temperature reporting. The oil temperature sensors are thermistor components and have a nominal resistance of 100 +10 ohms -10 ohms at ambient IDG case temperature.

(9) IDG servicing

(a) IDG oil pressure filling

A quick-filling coupling is installed on the transmission casing for pressure filling. The oil pumped into the IDG, through the pressure fill port, flows through the filter and then through the external oil circuit and into the IDG case.

The air that is in the circuit is pushed out by the oil and released through the open overfill-drain port.
When the oil level in the IDG sump become stable at the top of the open overfill standpipe, the level in the IDG system is correct.

NOTE: Motoring is not necessary for oil level check or oil replenishment.

(b) Vertical oil-level sight-glass
Different colors (red, yellow, green), related to the oil level, show when the oil servicing of the IDG is necessary.

(c) IDG reset ring
A mechanical reset ring is installed on the IDG. The handle is used to connect the drive again while the engine is stopped and stationary on the ground.

(10) The IDG is an Line Replaceable Unit (LRU).

B. IDG Fuel/Oil Heat-Exchanger

IDG Fuel/Oil Heat-Exchanger ** ON A/C NOT FOR ALL

(1) The IDG fuel/oil heat-exchanger controls the supply oil temperature to the IDG. It is installed downstream of the IDG oil/oil heat-exchanger.

(2) The IDG fuel/oil heat exchanger transfers heat from the IDG oil to the engine fuel. The cooled IDG oil is sent to lubricate and cool the IDG.

(3) The IDG fuel/oil heat-exchanger has internal tubes through which the engine fuel flows. These tubes go through the IDG oil core which has baffles to increase the surface area for heat transfer.

(4) The IDG fuel/oil heat-exchanger includes an oil bypass valve that helps to keep the IDG-oil minimum temperature:
The oil from the IDG that is not cooled is mixed with the cooled oil from the IDG fuel/oil heat-exchanger.

(5) The oil bypass valve is a viscosity control valve that operates independently from the Electronic Engine Control (EEC) (passive operation).

(6) At engine start-up, when the IDG oil temperature is low, the valve is in the full bypass position.

(7) At moderate temperatures, the valve controls the oil flow. In this position, the valve mixes the oil from the IDG that is not cooled and the cooled oil from the fuel/oil heat-exchanger. Then it sends the oil back to the IDG.

(8) At the high limit of the IDG-oil temperature range, the valve is in non-bypass (full cooling) position and 100 percent of the IDG oil flows through the fuel/oil heat-exchanger.

(9) The IDG fuel/oil heat-exchanger is a LRU.

C. IDG Power Cables

IDG Power Cables ** ON A/C NOT FOR ALL

(1) Four IDG power cables supply IDG-generated 115VAC/400 Hz power to operate the aircraft electrical systems.

(2) The IDG power cables are connected independently (not as a bundle) to terminal blocks at each end. Line blocks and clamps hold the cables in position along the left side of the engine core.

(3) The IDG power cables are LRUs.

D. IDG Power-Cables Disconnect-Blocks

IDG Power-Cables Disconnect-Blocks (Upper) ** ON A/C NOT FOR ALL

IDG Power-Cables Disconnect-Blocks (Lower) ** ON A/C NOT FOR ALL

(1) The IDG power-cables disconnect-blocks make it possible to remove and replace the IDG power cables independently. They also make quick removal of the IDG easier.

(2) The IDG power-cables disconnect-blocks have four threaded studs with nuts for cable connections. The are insulated fins between the studs.

(3) The IDG power-cables disconnect-block are LRUs.

E. IDG QAD Adapter

IDG QAD Adapter ** ON A/C NOT FOR ALL

(1) The IDG QAD adapter is used for quick replacement of the IDG.

(2) The IDG QAD adapter-kit,includes a gasket for the main gearbox mounting-pad , and has the components that follow:

(a) QAD ring - mates with the IDG input flange.

(b) QAD ring lugs - mate with the IDG input-flange lugs. The IDG is correctly installed when the white open-position marks on the IDG and QAD ring align.
In this position, the locator pin on the IDG is aligned with the locator hole in the QAD ring.

(c) Tension bolt - tightened to engage the IDG flange lugs into the QAD ring until the ring turns into the locked position.

(3) The IDG QAD adapter is an LRU.

F. IDG Fuel/Oil Heat-Exchanger Pressure-Sensor

IDG Fuel/Oil Heat-Exchanger Pressure-Sensor ** ON A/C NOT FOR ALL

(1) The IDG fuel/oil heat-exchanger pressure-sensor monitors the pressure change that occurs when the fuel/oil heat-exchanger becomes clogged. This occurs specially when there is contamination of the fuel or the fuel freezes.

(2) The IDG fuel/oil heat-exchanger pressure-sensor will send a signal to the upper ECAM DU when there is an unusual pressure change.

(3) The IDG fuel/oil heat-exchanger pressure-sensor is an LRU.

G. IDG Oil/Oil Heat-Exchanger

IDG Oil/Oil Heat-Exchanger ** ON A/C NOT FOR ALL

(1) The IDG oil/oil heat-exchanger controls the supply oil temperature to the IDG. It is installed upstream of the IDG fuel/oil heat-exchanger.

(2) The heat is transferred to and from the engine oil to the IDG oil in relation to the operating conditions. In most conditions, the heat is transferred from the engine oil to the IDG.

(3) The IDG oil/oil heat-exchanger uses a bypass valve.

(4) The IDG oil/oil heat-exchanger is an LRU.

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7. Operation/Control and Indicating

IDG Oil/Oil Heat-Exchanger ** ON A/C NOT FOR ALL

A. Monitoring of the Oil System Operation

IDG System - Generator Drive Control and Indicating ** ON A/C NOT FOR ALL

Speed Regulation Loop ** ON A/C NOT FOR ALL

(1) Oil temperature sensors monitor oil-in and oil-out temperatures for overheat detection.
A pressure switch operates when the charge oil pressure decreases.
In these two conditions, a warning is sent to the upper ECAM DU and the FAULT legend of the related pushbutton switch comes on.

(2) The oil-out temperature is shown on the ECAM electrical page.

NOTE: At a set oil temperature value, an advisory mode is shown on the lower ECAM DU.

B. Disconnection of the IDG

IDG1 Oil Low Pressure - Upper and Lower ECAM Display Unit ** ON A/C NOT FOR ALL

IDG 1 Oil Overheat - Upper and Lower ECAM Display Unit ** ON A/C NOT FOR ALL

IDG 1 Oil Overheat Advisory - Upper and Lower ECAM Display Unit ** ON A/C NOT FOR ALL

(1) On the ELEC section, the amber FAULT legend of the IDG 1(2) pushbutton switch comes on and the master warning system starts if:

There is an oil overheat (when the temperature of the oil that comes out of the IDG is high).
The oil pressure decreases but not because of the drive underspeed.

When the operator opens the safety guard and pushes the IDG 1(2) pushbutton switch on the ELEC section of overhead panel 35VU, the operator energizes the disconnected solenoid. Thus, the input shaft of the IDG becomes disengaged.

The FAULT legend of the IDG 1(2) pushbutton switch cannot be on during the engine shutdown (underspeed).
The FAULT legend of the IDG 1(2) pushbutton switch goes off when the IDG disconnection occurs (speed less than 2000 rpm).

If the IDG operates for more than 50 hours in the disconnected mode without a reset, the operator must replace it and send the removed IDG for a shop inspection. This is because there is a risk of damage to the ball bearing assembly on the input shaft and to the aircraft engine. After the IDG disconnection, the operator must not connect it again.

(2) The operator must not disconnect the IDG when the engine is stopped.
The operator cannot connect the IDG in flight. The connection of the system is then possible only on the ground with engines stopped. To connect the IDG in flight, the operator must move the pawl with the IDG reset ring.

C. Connection of the IDG

(1) Mechanical reset handle
The mechanical reset handle is used to connect the drive while the engine is stopped on the ground.

D. Oil Filter

(1) A local visual pop-out indicator shows when the oil filter is clogged. The indicator is installed opposite the drive end of the IDG.

[Rev.10 from 2021] 2026.03.31 23:19:33 UTC