Electrical Flashcards
EPGDS?
Electrical power generation and distribution system
What makes up the DC system?
3 batteries
2 Engine driven starter generators
2 TRUs
1 APU
DC external power
What are the batteries?
3 Nickel Cadium (Nicad) batteries
40 amp hour
24 volts DC
Main, Aux, Standby
What are the generators rated too?
400 Amps max
How many volts are the generators?
28.5 V DC
What are the TRUs max amp?
300
28 V DC
What is the APU max amps?
400
AC electrical system includes?
2 engine driven generators mounted in the prop reduction gearbox
AC external power receptacle
What do the AC gen’s produce?
115 V threes phase variable frequency AC power
EPCU?
Electrical power control unit reconfigures the system if there is a power source failure or bus fault
Can the AC gens power the whole electrical system
Yes
Where are the main and aux batteries?
Aircraft nose compartment left side
Are the main and aux battery used to assist engine starting even when external DC power is connected?
Yes
Where is the standby battery?
Left nose compartment upper (in the compartment above the other two batteries)
Can the standby battery power the L DC MAIN BUS?
No one way power so it only gets charged
Purpose of standby battery? (2 things)
Supply power to essential bus during an electrical emergency mode.
It also provides protection by absorbing voltage and current spikes
How long Backup electrical power in flight provided by the batteries?
Approx 60mins
What is the hot battery bus powered by?
Standby battery
Battery Bus powers?
• CLOCKS ONE & TWO
• BATTERY MASTER SWITCH
• BATTERY POWER FOR REFUELING
• FIRE BOTTLES DISCHARGE SQUIBS
• FUEL & HYDRAULICS SHUTOFF VALVES
• ENGINE FUEL METERING UNITS
• CARGO COMPARTMENTS FIRE SYSTEMS
• APU FIRE BOTTLE SQUIB-MANUAL DISCHARGE
• FLIGHT DECK DOME LIGHTS & BOARDING LIGHTS
• EMERGENCY POWER-PASSENGER ADDRESS SYSTEM
Switched battery power bus is powered by?
Either main batt, aux batt or left ess bus
What does the switched battery power bus supply power to?
Electronic integrated standby instrument (EISI)
#1 VHF receiver and standby control head
Storm lights and CCT breaker lights
Back lighting for compass
Turning battery master on does what?
Connects the 3 batteries to the essential buses
What batteries connect to the R ess bus?
Main and standby
What does the aux battery connect to?
Left essential bus which also powers the switched battery bus
The EPCU is powered by?
Essential buses
MAIN BATT switch on does?
Ties the main battery to the Right Main DC Bus and the switch batter power bus. Two way flow from main battery to right main dc bus
AUX BATT switch on?
Connects aux batt to Left Main DC bus and switch batter power bus.
Two way power flow between aux bat and left main dc bus
STBY BATT on?
Connects standby batt to the Left Main DC Bus. One way only to change to standby battery
If there is a bus fault or during emergency electrical ops what prevents the batteries being connected to the Main DC buses?
EPCU logic
Battery caution lights illuminated when?
When the battery are switched off or if there is an electrical fault and it has been automatically disconnect from its respective bus
How to monitor battery loads?
Electrical systems pages on either MFD (ENG SYS button)
What lights will you get if there is a batter overheat?
Warning light
STBY BAT HOT
AUX BAT HOT
MAIN BAT HOT
Battery overheat temp?
> 71 degrees = warning lights
<63 degrees = warning lights extinguish
What are the 6 DC buses that are powered by external DC power on the ground?
2 Ess buses
2 main buses
2 secondary buses
If the ground power malfunctions (over or under voltage) what happens?
> 31 volts or <22 volts. The EPCU auto disconnects the external power source. After the malfunction is rectified then the DC external power switch need to be cycled which will also reset the EPCU protection logic
What do the Gen 1 and Gen 2 switches do?
Control the engine driven DC started generators
What position are Main to secondary bus ties prior to AC generators online?
They are closed to allow the secondary buses to be powered because the ac gens come online
Secondary buses powered by?
AC generators through the TRUs. To get the AC gens online the condition levers must be forward of 850 RPM
DC start Gen mounted?
Right side of the engines accessory gearbox and are air cooled