GENERAL
There are two identical engine driven generators called Integrated Drive
Generators (IDGs). They are used as the main power source to supply
the A/C electrical network.
The IDG
basically contains, in a common housing, a generator and a
Constant Speed Drive (CSD). The CSD gives a constant input speed to
the generator, which is required for a constant output frequency.
Each generator supplies 115V 400Hz AC to its own bus:
– generator 1 supplies AC bus 1,
– generator 2 supplies AC bus 2.
This supply is known as split operation, which means that the AC power
sources are never connected in parallel.
Each AC bus supplies a Transformer Rectifier (TR):
– AC bus 1 supplies TR 1,
– AC bus 2 supplies TR 2.
The TRs convert 115V AC into 28V DC to supply their associated DC
buses, DC 1 and DC 2.
DC bus 1 then supplies the DC BATtery bus.
The DC BAT bus can charge the batteries or receive power from the
batteries as a backup supply, if no other power sources are available.
The electrical system also includes two ESSential (ESS) Buses. One is
the AC ESS bus fed by AC bus 1 and the other is the DC ESS bus fed
by DC bus 1. These buses are used to supply the most critical A/C
systems.
This is the basic electrical system. We will now introduce some other
components which also supply the system.
The APU generator can also supply the entire electrical network.
On the ground, the aircraft electrical network can be supplied by an
external power source.
Any one of the power sources can supply the entire electrical network.
As no parallel connection is allowed on this A/C (split operation), we
have to give priorities to the different power sources in supplying the bus
bars.
AC 1 and AC 2 buses are supplied in priority by their own side generator,
then the external power, then the APU generator and then by the opposite
generator.
There are two identical engine driven generators called Integrated Drive
Generators (IDGs). They are used as the main power source to supply
the A/C electrical network.
The IDG
basically contains, in a common housing, a generator and a
Constant Speed Drive (CSD). The CSD gives a constant input speed to
the generator, which is required for a constant output frequency.
Each generator supplies 115V 400Hz AC to its own bus:
– generator 1 supplies AC bus 1,
– generator 2 supplies AC bus 2.
This supply is known as split operation, which means that the AC power
sources are never connected in parallel.
Each AC bus supplies a Transformer Rectifier (TR):
– AC bus 1 supplies TR 1,
– AC bus 2 supplies TR 2.
The TRs convert 115V AC into 28V DC to supply their associated DC
buses, DC 1 and DC 2.
DC bus 1 then supplies the DC BATtery bus.
The DC BAT bus can charge the batteries or receive power from the
batteries as a backup supply, if no other power sources are available.
The electrical system also includes two ESSential (ESS) Buses. One is
the AC ESS bus fed by AC bus 1 and the other is the DC ESS bus fed
by DC bus 1. These buses are used to supply the most critical A/C
systems.
This is the basic electrical system. We will now introduce some other
components which also supply the system.
The APU generator can also supply the entire electrical network.
On the ground, the aircraft electrical network can be supplied by an
external power source.
Any one of the power sources can supply the entire electrical network.
As no parallel connection is allowed on this A/C (split operation), we
have to give priorities to the different power sources in supplying the bus
bars.
AC 1 and AC 2 buses are supplied in priority by their own side generator,
then the external power, then the APU generator and then by the opposite
generator.
SERVICING
CHECK OF THE OIL LEVEL AND FILTER DPI
Each engine (HP rotor) drives its related Integrated Drive Generator
(IDG) through the accessory gearbox.
The drive speed varies according to the engine rating. The IDG internal
gearing, converts the variable gearbox frequency to a stable 400 Hz.
The IDG supplies a 115 V AC, 3-phase, and 400 Hz AC. At some
point, servicing will be required of the IDG. In this module you will
see a video that will demonstrate the correct servicing procedures of
the IDG.
Check the oil level and the filter Differential Pressure Indicator (DPI)
each 150 Flight Hours (FH) or each times the engine cowls are opened.
Depending on when the time schedule occurs there might be a reason,
during transit checks, that you must check the oil level and the filter
DPI each 150 FH or each time the engine cowls are opened.
On each engine, use the sight glass that is in the vertical position to
do the check of the oil level. If it is below the green band or above
the yellow band, do the oil servicing.
Clogged filter indication is provided by a visual pop out indicator (the
DPI) mounted on the IDG. This indicator is installed opposite the
drive end of the IDG.
OPERATIONAL TEST OF THE IDG DISCONNECT AND
RECONNECT FUNCTION
The IDG will be disconnected in case of:
– oil overheat (high oil out temperature),
– oil pressure drop when not caused by drive under speed.
The amber FAULT legend of the ELECtrical/IDG1 or 2 P/BSW comes
on, the master warning system is triggered.
In this case, the IDG must be disconnected manually. For this, the
PUSH-TO-DISConnect IDG1 (2) safety guarded P/BSW, installed
on the panel 35 VU, must be pushed.
CAUTION: ENGAGE THE IDG DISCONNECT MECHANISM
WITH THE DISCONNECT RESET RING BEFORE
YOU START THE ENGINE. IF NOT, YOU WILL
CAUSE DAMAGE TO THE GEAR TEETH, AT
ENGINE START.
YOU CAN DAMAGE THE DISCONNECT SOLENOID
BECAUSE OF OVERHEATING IF: YOU PUSH THE
IDG DISCONNECT P/BSW FOR MORE THAN 3
SECONDS. THERE MUST BE AT LEAST 60
SECONDS BETWEEN 2 OPERATIONS OF THE
SWITCH.
On the ELEC control panel, push the IDG 1 (2) P/BSW.
On the IDG 1 (2), slowly pull out the disconnect reset ring to the full
limit of travel. If you feel a click while you hold the disconnect reset
ring, this shows that the disconnect function operates correctly. Let
the disconnect reset ring go slowly back to the initial position.
NOTE: The IDG disconnection is irreversible in flight. Reconnection
of the system is then possible only on the ground with
engines shut down.
CHECK OF THE OIL LEVEL AND FILTER DPI
Each engine (HP rotor) drives its related Integrated Drive Generator
(IDG) through the accessory gearbox.
The drive speed varies according to the engine rating. The IDG internal
gearing, converts the variable gearbox frequency to a stable 400 Hz.
The IDG supplies a 115 V AC, 3-phase, and 400 Hz AC. At some
point, servicing will be required of the IDG. In this module you will
see a video that will demonstrate the correct servicing procedures of
the IDG.
Check the oil level and the filter Differential Pressure Indicator (DPI)
each 150 Flight Hours (FH) or each times the engine cowls are opened.
Depending on when the time schedule occurs there might be a reason,
during transit checks, that you must check the oil level and the filter
DPI each 150 FH or each time the engine cowls are opened.
On each engine, use the sight glass that is in the vertical position to
do the check of the oil level. If it is below the green band or above
the yellow band, do the oil servicing.
Clogged filter indication is provided by a visual pop out indicator (the
DPI) mounted on the IDG. This indicator is installed opposite the
drive end of the IDG.
OPERATIONAL TEST OF THE IDG DISCONNECT AND
RECONNECT FUNCTION
The IDG will be disconnected in case of:
– oil overheat (high oil out temperature),
– oil pressure drop when not caused by drive under speed.
The amber FAULT legend of the ELECtrical/IDG1 or 2 P/BSW comes
on, the master warning system is triggered.
In this case, the IDG must be disconnected manually. For this, the
PUSH-TO-DISConnect IDG1 (2) safety guarded P/BSW, installed
on the panel 35 VU, must be pushed.
CAUTION: ENGAGE THE IDG DISCONNECT MECHANISM
WITH THE DISCONNECT RESET RING BEFORE
YOU START THE ENGINE. IF NOT, YOU WILL
CAUSE DAMAGE TO THE GEAR TEETH, AT
ENGINE START.
YOU CAN DAMAGE THE DISCONNECT SOLENOID
BECAUSE OF OVERHEATING IF: YOU PUSH THE
IDG DISCONNECT P/BSW FOR MORE THAN 3
SECONDS. THERE MUST BE AT LEAST 60
SECONDS BETWEEN 2 OPERATIONS OF THE
SWITCH.
On the ELEC control panel, push the IDG 1 (2) P/BSW.
On the IDG 1 (2), slowly pull out the disconnect reset ring to the full
limit of travel. If you feel a click while you hold the disconnect reset
ring, this shows that the disconnect function operates correctly. Let
the disconnect reset ring go slowly back to the initial position.
NOTE: The IDG disconnection is irreversible in flight. Reconnection
of the system is then possible only on the ground with
engines shut down.
FILLING OF THE IDG WITH OIL OR ADDITION OF
OIL
Make the thrust reverser unserviceable,
Depressurize the IDG case,
CAUTION: USE ONLY APPROVED TYPES/BRANDS OF
LUBRICANTS. DO NOT MIX TYPES/BRANDS OF
LUBRICANTS.
Fill the IDG with filtered oils at a maximum pressure of 35 PSI (2.4131
bar),
Inspect the oil level before and after the related engine start. Inspect
the oil level after it becomes stable (5 minutes after running),
If the oil level is at or near the top of the green band, oil servicing is
not necessary. If the oil level is below the green band or above the
yellow band, servicing is necessary.
OIL
CAUTION: USE ONLY NEW CANS OF OIL WHEN YOU FILL
THE IDG WITH OIL OR ADD OIL TO THE IDG. THE
CONTAMINATION IN THE OIL RAPID
DETERIORATION OF THE OIL AND WILL
DECREASE THE LIFE OF THE IDG.Make the thrust reverser unserviceable,
Depressurize the IDG case,
CAUTION: USE ONLY APPROVED TYPES/BRANDS OF
LUBRICANTS. DO NOT MIX TYPES/BRANDS OF
LUBRICANTS.
Fill the IDG with filtered oils at a maximum pressure of 35 PSI (2.4131
bar),
Inspect the oil level before and after the related engine start. Inspect
the oil level after it becomes stable (5 minutes after running),
If the oil level is at or near the top of the green band, oil servicing is
not necessary. If the oil level is below the green band or above the
yellow band, servicing is necessary.
MAINTENANCE TIPS
It must be mentioned here that the most typical reason for IDG failures
are due to over servicing. You must pay particular attention to the level
of the oil in the sight glass.
When servicing, leave the drain hose attached until only a couple of drops
come out.
It must be mentioned here that the most typical reason for IDG failures
are due to over servicing. You must pay particular attention to the level
of the oil in the sight glass.
When servicing, leave the drain hose attached until only a couple of drops
come out.
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