ELECTRICAL Flashcards
IDG (Integrated Drive Generators)
• Primary AC power source
• One on each engine
• AUTO - system logic controls contactor
• OFF - opens contactor
* DISC - mechanically disconnects the CSD (Constant Speed Drive) from the IDG
• Flight crew cannot reconnect the IDG (maintenance function only)
* Amber light when accompanied by an EICAS oil message indicates IDG disconnect is required.
AC POWER
• 2 IDGs (Integrated Drive Generators) - 115VAC, 400Hz, 40KVA
• 1 APU Generator - 115VAC, 400Hz, 40KVA
• 1 AC GPU (Ground Power Unit) - 115VAC, 400Hz, 40KVA
• 1 RAT (Ram Air Turbine) - 115VAC, 400Hz, 15KVA
• 1 Inverter - 250V
• 1 IDG can power both AC buses:
On ground
In flight
• APU can power both AC buses
On ground
In flight up to FL330
• GPU can power both AC buses
APU (Auxiliary Power Unit)
• Secondary AC power source
• BATT 1 and 2 or BATT 1 and the DC GPU are required for APU start
• BATT 1 is used to control the APU’s FADEC
BATT 2 is isolated from the network during APU start to exclusively power the APU START BUS
- 22.5 VDC minimum must be noted during the Safety &Power On Checklist to consider APU start
- 18.0 VDC minimum required to close the battery contactor
- Minimum BATT 2 temperature for start is -20°C
AC GPU (Ground Power Unit)
• Secondary AC power source
• Can be turned ON via three different buttons
One located on the AC GPU panel (only powers the ground service bus)
One located opposite the FWD lavatory (only powering the ground service bus)
One located in the cockpit on the overhead panel
* CAS message, MASTER CAUTION, and aural warning will occur should the
parking brake be released and the GPU is still connected to the aircraft
• AVAIL - GPU is properly connected and power requirements are satisfied
• IN USE - powering AC system
Normal AC Electrical Priority
- Onside (IDG)
- Inside (APU)
- Outside (GPU)
- Cross-Side (Other IDG)
Inverter
Powers the AC STANDBY BUS when normal AC power is not available so that “A” igniters always have a source of power.
RAT (Ram Air Turbine)
• Emergency AC power source
• No altitude or airspeed restriction for deployment
* Automatically deploys if both AC buses lose power during (electrical emergency) to supply the ESS buses
• Manual deployment is available if necessary
During deployment (approximately 8 seconds) the aircraft’s batteries provide power
• A minimum of 130 knots airspeed is required
• Below 130 knots
RAT will provide power only to AC ESS
BATTS will provide power to DC ESS and AC STANDBY
As airspeed decreases, load shedding occurs until AC ESS is no longer powered.
DC POWER
- 3 TRUs (Transformer Rectifier Units) - 28VDC, 300A
- 2 Batteries - 24VDC, 27AH
- 1 DC GPU - 28VDC
- 3TRUs (Transformer Rectifier Units) 28VDC, 300A
* Primary DC power source
* Converts 115VAC into 28VDC
* Each works in isolation from the other
Batteries
• Secondary DC power source
• 2 NiCad batteries
• Back-up for DC ESS
• Charged via any AC power source through the TRUs
• 18.0 volts minimum required to close the battery contactor
• Will provide 10 minutes of power during an electrical emergency
* Charged by an AC source
* Min T for APU start -20°C
DC GPU
- Can replace BATT 2 during APU start
* Can only be turned on by a ground ramp button
ELECTRICAL POWER DISTRIBUTION
ICC (Integrated Control Center)
• 4 (Installed in various Electrical Bays)
• Line-replaceable (Plug-n-Play like a computer’s motherboard)
SPDAs (Secondary Power Distribution Assemblies)
• An electrical load management unit
• Receives power from ICCs
• Distributes power according to system logic
In simple terms...the ICCs collect and confirm the power is safe and then
sends it to the SPDA, which distributes it.
What will cause the amber IDG light on the overhead panel to illuminate?
♣ High oil temperature
♣ Low oil pressure
What battery is used for the APU start?
♣ BATT 2 powers the APU Start bus
♣ BATT 1 powers the FADEC & EICAS for monitoring
Can the flight crew reset the ICC and SPDA remote electronics CB’s?
♣ ICC CB’s can only be reset by maintenance on the ground
♣ SPDA CB’s can be reset via the MCDU
