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3 Major Systems
- DC Electrical
- AC Electrical
- STBY Power System
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DC Electrical
- Tied in parallel
- Share and balance electrical loads
- 3 Sources
- -- A/C battery
- -- GPU
- -- Left/Right hand Load bus
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DC Power Source Components:
Starter Generators
- 28Vdc, 400amp engine driven generators
- Mounted on front of engine driven accessory gear box
- Provide starting torque to engines until 35-40% N2 then switch to generators
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DC Power Source Components:
Generator Control Units (GCU)
- Monitor generators and switch them from starters to generators
- Provide Fault Protection
- Reverse Current Protection
- Load Sharing
- Over voltage protection
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DC Power Source Components:
Battery
- Located in aft fuselage
- 24Vdc lead acid
- Approximately 30 minute life span
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DC Power Source Components:
Battery Feeder Protection Unit
- Detects ground faults that may occur in battery and external power feeder and ground lines
- If fault occurs-
- -- Illuminates red BATT FDR FAIL
- -- Deenergizes the battery relay and battery tie-in relays which illuminate BATT CUT OFF and EMER BUS FDR FAIL
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DC Power Source Components:
External Power Receptacle
- 28 –28.5Vdc
- 1,000 – 1,500amps
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DC power distribution system
- -- Primary power distribution from Main Buses to Load Buses
- -- The Battery charge bus acts as a connection bus for all DC power
- -- L/R BUS FDR FAIL annunciator means third feeder line between Main and Load bus is active. Will shut off if third line c/b trips
- -- Feeder lines between Main and Load buses are have two c/b on each of them one 100amp RCCB and 1 ½ amp c/b
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Secondary Power distribution
- (9 buses)
- L/R load bus
- L/R nonessential bus
- L/R overhead bus
- L/R radio master bus
- Standby bus
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AC Power Supply
- 2 inverters
- -- Supply 115Vac and 26Vac single phase electrical power at an apparent power rating on 250voltamperes each
- -- Located in the nose of the aircraft
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AC Power Distribution Controls
- -- Inverter selector switch is located in the main circuit breaker panel
- -- AUTO means the number one inverter supplies power to primary buses and number 2 provides power to secondary buses
- -- NO. 1 position forces the number one inverter to supply power to primary buses and number 2 to secondary buses
- -- This bypasses the number one inverter fault sensing circuits, but not the number 2 fault sensing circuits
- -- NO. 2 position forces the number 2 inverter to power the primary buses and the number 1 to power the secondary buses
- -- In this case all fault sensing circuits are bypassed
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AC BUS SHED indicator illuminates when:
- Number 1 inverters is not supplying 115Vac
- Number 2 inverter is on
- Number 2 inverter power relay is deenergized
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DC Standby battery
- 24Vdc lead acid
- Located in nose electronics compartment
- STBY PWR ARM means the standby battery is connected to the standby bus
- STBY PWR ON means the standby battery is the only source powering the standby bus
- If STBY PWR is not armed it will not automatically be powered with lost of all electrical power
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DC Standby AHRS battery
- 24Vdc lead acid
- Located in avionics rack
- Provides power to either or both AHRS computers if the Left and/or Right Load buss power fails
- Power is provided for up to 10 or approximately 11 minutes depending on where you look in the dash one
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Emergency Power
- Normally receives power from generators through battery
- If EMER BUS FDR FAIL illuminates power is supplies through LH load bus
- With battery in EMER power is from the battery only
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Standby Power Bus
- (CRUISSE)
- Co-pilot lights
- RTU #1
- UHF radio
- ITT (left)
- Standby attitude indicator
- Standby altimeter
- EFC for engine start
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Emergency Power Bus
- (SLEEVES)Standby bus
- Landing Gear lights
- Engine Ignition & control
- Emergency pitch trim
- VHF Nav 1
- Engine Fire Detect/Fuselage Smoke Detector
- Selected LH instrument
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AC Instruments
- 26 VAC Primary Shed
- --Flap Position --R/L Oil Pressure
- 115 VAC Primary --GPWS
- 26 VAC Primary-- Pitch Trim Position Indicator
- 26 VAC Secondary-- GRE
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Generator Control Units
- Provide Fault Protection
- Reverse Current Protection
- Load Sharing
- Over voltage protection
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