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)
- 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 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 –
- TRANSFORMER RECTIFIERS (TRs) – UP TO 200 A OF DC
- TR1 – AC BUS 1 (GEN1)
- TR2 – AC BUS 2 (GEN2)
- ESSENTIAL TR – EMER GEN
- 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 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/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
- Split Busbar System – Two supplies cannot be connected together.
- That’s why – 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
- 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
- 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.
- 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.
- 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 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.
- 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
- 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.
- 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
- GAPCU has an interface with CFDIU
- GCU 1 / GCU 2 > GAPCU > CFDIU
- CSM/G GCU – directly to CFDIU
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.