AVIONICS-AS-PPT-2-ELECTRICAL-GENERATING-EMERGENCY-POWER-DISTRIBUTION-SYSTEMS-1

Aircraft Avionics And Autopilot Systems (AVIONICS- AS)

Aircraft Electrical Generating System

  • Overview of electrical power systems in aircraft, including operation and control.

  • Importance of electrical power for control, operation, and indication of systems during flight and on the ground.

Electrical Power Sources

  • Categories of Electrical Power Sources:

    • Primary Power Sources:

      • Main generators

      • Inverters

      • Transformers

    • Secondary Power Sources:

      • Electronic power supplies

      • Emergency/backup power sources (e.g., emergency generators, batteries, external power supplies).

System Description

  • Electrical power types:

    • Battery (DC)

    • Generators (AC)

    • Ground Support Equipment (GPU) (AC or DC).

  • Electrical power distribution standards: 115 volts AC and 28 volts DC.

General Component Locations

  • Electrical power distribution:

    • Two engine-driven generators supply AC during flight.

    • Auxiliary power unit (APU) provides all necessary power when the aircraft is on the ground.

    • External power can be supplied via an AC receptacle.

    • DC power sourcing:

      • From batteries or converted AC power.

AC Generator System

  • AC generators provide the necessary AC electrical power:

    • Output: 115/208V, 3-phase AC power at a constant frequency of 400 Hz.

    • Generators driven by engines/APU to maintain constant speeds.

Auxiliary Power Unit (APU)

  • The APU allows autonomy for the aircraft without ground support.

  • Powers onboard lighting, galley equipment, and cockpit avionics.

  • APU also drives environmental packs for heating and cooling.

AC Generator System (continued)

  • Network System:

    • Comprised of three 3-phase, 400 Hz AC generators.

    • Isolated generators located on engines and the APU.

    • Utilizes transformers for voltage regulation to 28 volts AC for instrument requirements.

Generator Control Unit (GCU)

  • Functions:

    • Regulates output and limits to ensure proper voltage.

    • Provides excitation power control and adjustment mechanisms.

    • Offers fault protection against abnormal system states (overvoltage, under-voltage, etc.).

Emergency Power Generation

  • Ram Air Turbine (RAT):

    • Extends in loss of AC power for emergency electrical backup.

    • Utilizes airspeed to generate power for critical systems.

Batteries

  • Emergency power source for electrical systems.

  • Common types: lead-acid (red) and nickel-cadmium (blue) batteries.

  • Chargers maintain battery charge during normal operations.

Electrical Distribution System

  • Power Distribution:

    • AC power routed through three main load buses.

    • Monitors for short circuits and over-current.

    • Each bus connects to generator outputs.

DC Generation System

  • DC Power Conversion:

    • 3-phase power converted to 28V DC via TR units.

    • Essential for control circuits and components.

    • Standby DC power provided by a Nickel-Cadmium storage battery.

Static Inverter**

  • Converts 28V DC to 115V AC for devices requiring AC power.

Electronic Equipment Compartment

  • Location: aft of the nose wheel well, housing critical components for monitoring and control.

DC Indications

  • Instruments:

    • DC Ammeter and Voltmeter on overhead panel for monitoring.