ATA 24 – ELECTRICAL POWER

  • A320 a/c is basically AC operated.
  • Electrical Power System
    • 115/200V 3 Phase 400Hz constant-frequency AC system
    • 28V DC system
  • 115 V – Phase Voltage (b/w phase and neutral)
  • 200 V – Line Voltage (b/w phase and phase)

AC GENERATION

  • MAIN GENERATORS
    • 115/200 volts, 3 Phase, 400 Hz, 90 KVA
    • GEN 1 (IDG 1) – ENG 1
    • GEN 2 (IDG 2) – ENG 2
    • Each IDG is controlled and monitored by its GCU.
    • GEN 1 – GCU 1
    • GEN 2 – GCU 2
  • APU GENERATOR & EXTERNAL POWER
    • 115/200 volts, 3 Phase, 400 Hz, 90 KVA
    • APU GEN – APU
    • EXT PWR – GPU
    • APU Generator can replace one or both main engine generators throughout the flight envelope.
    • A Ground and Auxiliary Power Control Unit (GAPCU) controls both the APU generator and the EXT PWR.
  • EMERGENCY GENERATOR
    • 115/200 volts, 3 Phase, 400 Hz, 5 KVA (NEO – 5.4 KVA)
    • EMER GEN (CSM/G) – RAT Hydraulic Circuit
  • STATIC INVERTER
    • 115 volts, 1 Phase, 400 Hz, 1 KVA
    • STAT INV – DC Power from Battery1
    • When the aircraft speed is above 50 kt, the inverter is automatically activated, if nothing but the batteries are supplying electrical power to the aircraft, regardless of the BAT 1 and BAT 2 pushbutton positions.
    • When the aircraft speed is below 50 kt, the inverter is activated, if nothing but the batteries are supplying electrical power to the aircraft, and the BAT 1 and BAT 2 pushbuttons are both on at auto.

AC DISTRIBUTION

  • AC BUS 1 – Supplied by ENG 1 GEN.
  • AC BUS 2 – Supplied by ENG 2 GEN.
  • AC ESS BUS – Normally supplied by AC BUS 1 or by AC BUS 2 if AC BUS 1 fails.
  • AC ESS SHED BUS – Supplied by AC ESS BUS.
  • AC STAT INV BUS – STAT INV connected to Battery 1 supplies the AC STAT INV BUS.
  • 26V AC BUS – Supplied by 115/26V AUTO TRANSFORMER.

AC POWER TRANSFER

  • The AC transfer circuit enables AC BUS to be supplied by any generator or external power, via the Bus Tie Contactors (BTCs).
  • BTC1 – 
  • BTC2 – 

DC GENERATION

  • TRANSFORMER RECTIFIERS (TRs) – UP TO 200 A OF DC
    • TR1 – AC BUS 1 (GEN1)
    • TR2 – AC BUS 2 (GEN2)
    • ESSENTIAL TR – EMER GEN
  • BATTERIES
    • Normal capacity of 23 AH (NEO – 28 AH) with a nominal voltage of 24V.
    • Permanently connected to the two hot buses.
    • Each battery has an associated Battery Charge Limiter (BCL).
    • The BCL monitors battery charging and controls its battery contactor.
      • BAT 1 – BCL 1
      • BAT 2 – BCL 2
    • COMPLETE DISCHARGE PROTECTION – On ground, when the battery voltage is lower than 23V DC for 15 s, the BCL supply contactor opens automatically.

DC DISTRIBUTION

  • DC BUS 1 – Supplied by TR1
  • DC BUS 2 – Supplied by TR2
  • DC BAT BUS – Supplied by DC BUS 1 or by DC BUS 2 if DC BUS 1 fails. Batteries can also supply DC BAT BUS.
  • DC ESS BUS – Supplied by DC BAT BUS. In emergency, it is supplied either by battery 2 or by essential TR.
  • DC ESS SHED BUS – Supplied by the DC ESS BUS.
  • HOT BUS 1 – Permanently supplied by Battery 1.
  • HOT BUS 2 – Permanently supplied by Battery 2.

GROUND SERVICE

  • GROUND/FLIGHT BUSES
    • AC GND/FLT BUS
    • DC GND/FLT BUS
  • Normally supplied by the aircraft network, or directly by the external power unit, upstream of the External Power Contactor (EPC), without energizing the whole aircraft network.
  • On ground, when only ground services are required, external power can supply the AC and DC GND/FLT BUSES directly without supplying the entire aircraft network. Personnel select this configuration with the MAINT BUS switch in the forward entrance area.
  • DC GND/FLT BUS through TR2

BUSBAR SYSTEM

  • Split Busbar System – Two supplies cannot be connected together.
  • That’s why – Priority Logics.

PRIORITY LOGICS

  • 1 – Onside generator (IDG)
  • 2 – External power
  • 3 – APU GEN
  • 4 – Offside generator (IDG)

NORMAL FLIGHT CONFIGURATION

  • IDG 1 > AC BUS 1 > TR 1 > DC BUS 1 > DC BAT BUS < BAT 1 > HOT BUS 1 & BAT 2 > HOT BUS 2.
    • AC BUS 1 > AC ESS > AC ESS SHED
    • DC BAT BUS > DC ESS > DC ESS SHED
  • IDG 2 > AC BUS 2 > TR 2 > DC BUS 2
    • AC BUS 2 > AC GRND FLT
    • DC BUS 2 > DC GRND FLT

EMERGENCY CONFIGURATION

  • RAT deployment conditions –
    • AC BUS 1 & AC BUS 2 – FAIL
    • Speed > 100 KTS
    • L/G not compressed – A/C in flight
  • EMER GEN > AC ESS > AC ESS SHED
  • EMER GEN > ESS TR > DC ESS > DC ESS SHED

NORMAL TO EMERGENCY

  • During time gap – before emergency gen connection. Till the time – 
  • BAT 1 > STAT INV > AC STAT INV
    • BAT 1 > HOT BUS 1
  • BAT 2 > DC ESS
    • BAT 2 > HOT BUS 2
  • When speed < 100 kts - EMER GEN deactivated.
    • 50 to 100 kts – DC BAT BUS recovered.
    • Below 50 kts – AC ESS BUS disconnected.
    • < 100 kts conditions – usually after landing.

BUS BAR IDENTIFICATION

  • XP – AC
  • PP – DC

IDG

  • Integrated Drive Generator consists of a – mounted side by side in a single housing.
    • Constant Speed Drive (CSD) and
    • AC Generator
  • CSD components convert a variable input speed to a constant output speed. 
  • CSD portion of the IDG is a hydromechanical device that adds to or subtracts from the variable input speed of the engine gearbox.
  • IDG is cooled and lubricated by the oil circulation system.
  • Oil is cooled by an external mounted IDG oil cooler.
  • IDG oil outlet temp. – display on SD.
  • IDG over voltage – 130 +/- 1.5 v
  • IDG over frequency – 435 +/- 1 Hz
  • IDG – PMG > 16 pole
    • GCU supply
    • Exciter field of generator for voltage regulation

If IDG HIGH OIL TEMP / LOW OIL PRESSURE

  • Indication –
    • Master caution
    • Single chime
    • ELEC IDG 1 (2) OIL OVHT / ELEC IDG 1 (2) LO PR
    • IDG p/b – Fault light
  • Action –
    • IDG must be disconnected by P/B manually.
    • Push IDG disconnection p/b for max of 3 sec.
    • Don’t press for more than 3 sec. because the IDG thermal disconnect solenoid is high current solenoid. It can burn/damage the solenoid.
    • Disconnection is only possible when the engine is running above underspeed.
    • Disconnection – Rod > push > hit > disconnect. Push by thermal disconnect solenoid.
    • Connection – Pull the reset ring.

GEN P/B

  • Used to connect or disconnect the generator output to or from the Bus Bar, and
  • To reset the GCU.
  • GEN 1, APU GEN, GEN 2 – P/B
  • P/B controls the GEN LINE CONTACTORS (GLCs) – 3 for each GEN.
  • GLC connects the generator to its own bus bar.

IDG P/B

  • IDG1, IDG2 – P/B
  • IDG P/BSW is used for manual disconnection of IDG from the engine gearbox.
  • With the engine stopped, the IDG cannot be manually disconnected.
  • IDG disconnection is achieved by a solenoid activated clutch.
  • IDG P/B FAULT legend comes on if the IDG oil pressure is less than 140 psi or if the IDG oil outlet temperature is above 185°C. In both conditions, the IDG must immediately be disconnected. When the IDG P/B is pushed, the FAULT legend goes out.

IDG THERMAL DISCONNECT

  • If the temperature reaches 200°C, a solder fuse melts and automatically releases the disconnect mechanism to open the IDG disconnect clutch. (To protect the IDG). A warning message is sent to the ECAM system and a BITE MESSAGE (THERMAL DISCONNECT) is sent to the CFDS.
  • After a thermal disconnection, the IDG must be replaced.

OPERATIONAL TEST OF THE IDG DISCONNECT AND RECONNECT FUNCTION

  • 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.
  • The IDG disconnection is irreversible in flight.
  • Reconnection of the system is then possible only on the ground with engines shut down.

IDG SERVICE TIPS

  • Fill the IDG with oils at a maximum pressure of 35 PSI.
  • When servicing, leave the drain hose attached until only a couple of drops come out.  >> avoid overservicing.

GEN 1 LINE P/B

  • In SMOKE configuration – Red SMOKE Light ON. (Avionics Smoke)
  • On activation of this p/b opens GLCs.
  • Fuel pumps are connected upstream of the GEN 1 GLC.
  • Generator stays energized to supply directly the fuel pumps 1 LH and 1 RH side.

APU GEN

  • APU generator is cooled and lubricated by the APU oil.
  • In case of oil temperature above 185°C, ECB commands > To shutdown the APU.
  • APU speed is not variable that’s why there is no CSD. Speed is almost constant. Speed control by FCU.

EXT POWER

  • External power has priority over the APU generator. The engine generators have priority over external power.
  • ON light stays on, even when the engine generators supply the aircraft.
  • Environmental Precautions – Avoid use of the APU if APU BLEED air is not necessary.

EXT PWR RECEPTACLE

  • 3 phase – 3 pin – A , B , C
  • 1 neutral – 1 pin – N
  • 2 small pin – E , F
    • DC supply to GAPCU – for control and protection, and validity of connection.
    • Reason for small – A,B,C pin properly connected then only E , F allow to supply the power.

SHORT CIRCUIT PROTECTION – PTC (for EXT power only)

  • Positive Temp. Coefficient Sensor
  • Red PTC trip LED on GAPCU

EMR GEN

  • Hydraulic motor is pressurized by the blue hydraulic system through an integrated solenoid valve. The hydraulic motor speed is regulated by a servo valve.
  • If both AC BUS 1 and AC BUS 2 are lost and the aircraft speed is above 100 kt, the Ram Air Turbine (RAT) extends automatically.
  • If AC BUS 1 and 2 are lost and the RAT does not extend, FAULT light comes on red on the EMERgency ELECtrical PoWeR panel (this is only indication not a p/b, that fault light is controlled by BCL). The RAT must be manually extended to power the emergency generator. This is done by pressing the guarded MANual ON P/BSW on the EMER ELEC PWR panel.
  • RAT MAN ON P/BSW on the blue hydraulic panel enables the extension of the RAT for hydraulic power supply only.
  • Activation of the red guarded “MAN ON” p/b on the ground or in flight will extend the RAT even on COLD AIRCRAFT.

RAT SOLENOID

  • Two – Solenoid 1 & Solenoid 2
  • Hot Bus supply – only – RAT MAN p/b (hyd panel) & Solenoid 1
    • p/b can deploy the RAT even if a/c is in cold condition.
  • RAT p/b on elec panel – not connected to Hot Bus.
  • Solenoid 1 – for auto deploy
  • Solenoid 2 – for manual deploy

CFDIU INTERFACE

  • GAPCU has an interface with CFDIU
  • GCU 1 / GCU 2 > GAPCU > CFDIU
  • CSM/G GCU – directly to CFDIU

CIRCUIT BREAKERS

The aircraft has two types of C/Bs:

  • Monitored (Green): When out for more than 1 min, the C/B TRIPPED warning is triggered on the ECAM.
  • Non-monitored (Black).
  • Wing Tip Brake (WTB) C/Bs have red caps on them to prevent them from being reset.
  • C/B TRIPPED warning on the ECAM indicates the location of the affected C/B.

COMPUTERS

  • GCU
  • GAPCU
AviationHunt Team

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