MAIN AC GENERATION ENGINE GENERATORS
The aircraft electrical system is supplied by two engine driven GENerators regulated in speed by integrated drives.
GEN 1 is driven by engine 1. GEN 2 is driven by engine 2.
Engine generators characteristics are:
- 115/200 volts, three phase,
- 400 Hz,
- 90 kVA.
APU GENERATOR
A third AC generator driven by the APU can replace one or both main engine generators throughout the flight envelope.
APU GEN characteristics are:
- 115/200 volts, three phase,
- 400 Hz,
- 90 kVA.
EXTERNAL POWER
A ground EXTernal PoWeR connector enables all bus bars to be supplied.
External power characteristics are:
- 115/200 volts, three phase,
- 400 Hz,
- 90 kVA minimum.
EMERGENCY GENERATOR
An AC EMERgency GEN is driven by the Ram Air Turbine (RAT) hydraulic circuit. It automatically provides emergency power in case of failure of all main aircraft generators. Emergency generator characteristics are:
The aircraft electrical system is supplied by two engine driven GENerators regulated in speed by integrated drives.
GEN 1 is driven by engine 1. GEN 2 is driven by engine 2.
Engine generators characteristics are:
- 115/200 volts, three phase,
- 400 Hz,
- 90 kVA.
APU GENERATOR
A third AC generator driven by the APU can replace one or both main engine generators throughout the flight envelope.
APU GEN characteristics are:
- 115/200 volts, three phase,
- 400 Hz,
- 90 kVA.
EXTERNAL POWER
A ground EXTernal PoWeR connector enables all bus bars to be supplied.
External power characteristics are:
- 115/200 volts, three phase,
- 400 Hz,
- 90 kVA minimum.
EMERGENCY GENERATOR
An AC EMERgency GEN is driven by the Ram Air Turbine (RAT) hydraulic circuit. It automatically provides emergency power in case of failure of all main aircraft generators. Emergency generator characteristics are:
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Front matter, or preliminaries, is the first section of a book and is usually the smallest section in terms of the number of pages. Each page is counted, but no folio or page number is expressed or printed, on either display pages or blank pages.
INTERFACES
The GCU interfaces with:
- The engine fire pushbutton switch. When pushed in, the generator is de-energized.
- Both SDACs for the ECAM monitoring.
- The CFDIU through the GAPCU (BITE type 1 data to CFDIU)
- The FADEC which gives the engine speed information.
OPERATION
In normal operation all internal relays of the GCU are energized. Through the energized contacts of the PRR, the de-energized contact of the BTC and the energized contacts of the AUX relay, the Generator Line Contactor (GLC) is then energized. The de-energized state of the BTC makes sure that there is no supply to the BUS before the Generator takes over the supply.
GEN FAULT
If the GEN pushbutton is in the "on" position and the PRR of the GCU is not energized, the fault light on the GEN pushbutton comes on by a ground due to the pushbutton position. The PRR is de-energized, among other reasons, when the voltage and frequency are not in tolerance. If the engine is not started, there is no regulation possible for both voltage and frequency. Therefore, the FAULT lighting is normal when the engine is not running.
GEN 1 LINE OFF
If the GEN 1 LINE pushbutton is released, the OFF legend comes on and the supply voltage to the AUX relay is interrupted. Since the contacts of the AUX relay now are in the de-energized position, the supply voltage to the GLC relay is interrupted. However, the Generator is still regulated and functioning normally to allow direct supply from the Generator to the electrically driven fuel pumps in both wings.
The GCU interfaces with:
- The engine fire pushbutton switch. When pushed in, the generator is de-energized.
- Both SDACs for the ECAM monitoring.
- The CFDIU through the GAPCU (BITE type 1 data to CFDIU)
- The FADEC which gives the engine speed information.
OPERATION
In normal operation all internal relays of the GCU are energized. Through the energized contacts of the PRR, the de-energized contact of the BTC and the energized contacts of the AUX relay, the Generator Line Contactor (GLC) is then energized. The de-energized state of the BTC makes sure that there is no supply to the BUS before the Generator takes over the supply.
GEN FAULT
If the GEN pushbutton is in the "on" position and the PRR of the GCU is not energized, the fault light on the GEN pushbutton comes on by a ground due to the pushbutton position. The PRR is de-energized, among other reasons, when the voltage and frequency are not in tolerance. If the engine is not started, there is no regulation possible for both voltage and frequency. Therefore, the FAULT lighting is normal when the engine is not running.
GEN 1 LINE OFF
If the GEN 1 LINE pushbutton is released, the OFF legend comes on and the supply voltage to the AUX relay is interrupted. Since the contacts of the AUX relay now are in the de-energized position, the supply voltage to the GLC relay is interrupted. However, the Generator is still regulated and functioning normally to allow direct supply from the Generator to the electrically driven fuel pumps in both wings.
GENERAL
The Generator Control Unit (GCU) 1 and 2 are identical and interchangeable. Pin programming provides the GCU with the following information:
- the aircraft type,
- the GCU position,
- the current limit for voltage regulation,
- the load limit.
The main functions of the GCU are:
- regulation of the generator voltage,
- regulation of the generator frequency,
- regulation of the generator speed (ServoValve (SV) control),
- control and protection of the network and the generator,
- interface with System Data Acquisition Concentrator (SDACs) for the ECAM,
- interface with Full Authority Digital Engine Control (FADEC) for engine speed,
- interface with Centralized Fault Display System (CFDS) via the Ground and Auxiliary Power Control Unit (GAPCU).
VOLTAGE REGULATION
The voltage regulation is achieved by regulating the current through the exciter field. The voltage is kept at a nominal value (115V AC) at the Point Of Regulation (POR). The POR is located at the end of the generator feeder upstream of the Generator Line Contactor (GLC). The output from the Permanent Magnet Generator (PMG) is connected via the Generator Control Relay (GCR) to the excitation and regulation control module for frequency monitoring use.
FREQUENCY REGULATION
The Integrated Drive Generator (IDG) frequency is regulated by a servovalve in the IDG and the servovalve control circuit in the GCU (via the SV relay).
The PMG frequency is compared with a GCU internal reference frequency. The difference generates a control current to drive the servovalve to produce the right output frequency.
CONTROL AND PROTECTION
The GCU control and protection functions are mainly performed by 3 internal relays:
- the GCR controls the generator excitation,
- the Power Ready Relay (PRR) controls the GLC,
- the SV relay controls the IDG speed.
If a protection function is triggered, the GCR, the PRR and, in some cases the SV relay, are de-energized.
UNDERSPEED
Engine speed information provided by FADEC is used to sense the IDG input speed. When engine speed falls below the underspeed threshold the PRR trips and the excitation is biased off due to underfrequency. In case of an absent FADEC speed signal to the GCU, a back-up signal is provided by the engine master switch to inform the GCU logic that the engine will shut down.
Note: in case of detected underspeed (e.g. engine shut down) no reset action via the GEN P/BSW is required.
OVERVOLTAGE
The GCU performs an overvoltage protection function. If the highest individual phase at POR reaches 130 ± 1.5 volts, the PRR and the GCR are tripped.
The higher the voltage, the faster the relays trip.
OVERFREQUENCY
The GCU performs an overfrequency protection function. If the frequency is above 435 ± 1Hz, for at least 4 seconds, the GCU trips the PRR and the GCR. If the frequency is above 452 Hz, for at least 160 milliseconds, the GCU trips the PRR, the GCR and also the SV relay.
OVERLOAD / OVERCURRENT
The IDG Current Transformers (CTs) provide current sensing information to the GCU. This information is used to determine generator load for overload, overcurrent, phase imbalance (delta) and also Differential Current Protection. In case of overload, the GCU sends signals to the SDAC for an ECAM message and to the FAULT light on the GALY &
CAB P/BSW.
If an IDG fails, the Bus Tie Contactors (BTCs) close and some galleys loads are automatically shed.
GCUs monitor BTC status and determine if overcurrent protection (BTC lockout) should be inhibited. If the galleys are not automatically shed the BTC lockout is inhibited, to allow the GALY & CAB P/BSW to be selected OFF.
