Electric Flashcards
The DC electrical system is supplied by:
3 NiCad batteries (24v DC)
2 Engine driven DC Starter-Generators (28.5v DC)
2 Transformer Rectifier Units (28v DC)
1 Auxiliary Power Unit (28v DC)
Name the 7 DC busses.
Battery
Left and Right Essential
Left and Right Main
Left and Right Secondary
The AC electrical system is supplied by:
2 engine driven AC generators that provide 115 volt, three-phase, variable AC power
Automatic reconfiguring of the electrical system is controlled by the…
Electrical Power Control Unit (EPCU).
Where are the batteries located?
Main and Aux - Lower Left section of nose compartment
Standby - Upper Left section of nose compartment
Volts and amp hours of batteries
Main and Aux - 24v, 40 amp hour
Standby - 24v 17 amp hours
Batteries that assist engine start
Main and Aux
How long will batteries supply emergency power?
Approximately 45 minutes
Which battery is connected to the “hot” battery bus
Standby battery
BATTERY MASTER switch
Closes 3 contactors directly connecting all three batteries to the Essential DC buses
How is the EPCU powered?
Indirectly from essential busses, Primarily from standby battery
MAIN/AUX/STBY BATT switch
Directly connects respective battery to its main bus
What busses is the main battery connected to?
Right main DC bus (2 way flow), Right Essential Bus
What busses is the aux battery connected to?
Left Main DC bus (2 way flow), Left Essential Bus
What busses is the standby battery connected to?
Left Main DC bus (1 way flow for charging), Right Essential Bus
Battery temperature range
Amber - 50C to 65C
Red - greater than 65C
What bus is external DC power is received by?
Left Main DC Bus
When will the EPCU automatically disconnect from the external power source?
External DC voltage exceeds 31 volts or drops below 22 volts
What are the DC starter-generators driven by?
Engine Accessory Gearbox
How are the DC starter-generators cooled?
Air cooled
How are the DC starter-generators monitored and controlled?
Respective Generator Control Unit (GCU)
At what point does the GCU convert the DC starter-generator from starter mode to generator mode?
Nh of 50% during start
What are the volts and amps of the DC starter-generators.
28.5 volts, 400 amps
How are the TRUs cooled?
Air cooled
What do the TRUs do?
Convert 115 volt 300 amp variable frequency AC power into 28 volt DC power
How can you manually control the TRUs?
Respective circuit breaker located on the 115 volt variable AC circuit breaker panel
What is the APU start-generator rated at?
28 volts, 400 amps
When does automatic load shedding occur?
Loss of more than two DC power sources
What is EPCU emergency mode?
Loss of both DC generators and one TRU
What happens during EPCU emergency mode?
EPCU automatically disconnects the batteries from the main busses leaving them only able to supply power to essential busses (approximately 45 minutes)
Can the engines be restarted in the air in EPCU emergency mode?
Yes, EPCU will allow batteries to be momentarily reconnected to main busses
What happens when the EPCU detects a bus fault?
Automatically takes offline all the DC components associated with the faulty bus via isolation
How are the AC generators cooled?
Oil cooled
How are the AC generators driven?
Propeller Reduction Gearbox
How are the AC generators rated?
115 volt, three phase, variable frequency AC power
What components are powered by AC power?
- deicing/anti-icing heaters
- standby hydraulic pump (#1 system)
- TRUs
- # 1 and #2 aux fuel pumps
- galley loads
Where are circuit breaker panels located?
- four flight compartment panels
- DC contactor box in nose compartment
- AC contactor box in left and right wheel well
- two wardrobe circuit panels
- galleys
1 or #2 DC GEN HOT caution light
DC generator temperature is more than 166C
1 or #2 AC GEN HOT caution light
AC generator temperature is more than 166C
1 or #2 DC GEN caution light
DC generator not connected to its bus due to a source fault condition, the DC toggle switch is set to OFF, or the external DC power is energizing the main feeder busses
1 or #2 AC GEN caution light
AC generator not connected to its bus due to a source fault condition, the AC toggle switch is set to OFF, or the external AC power is energizing the main feeder busses
STBY/MAIN/AUX BATTERY caution light
battery is not connected to its main feeder bus for charging
L or R TRU HOT caution light
TRU temperature is more than 71C
L or R TRU caution light
AC secondary feeder bus not energized by its related TRU because of a source fault condition or the AC generator toggle switches are set to OFF
DC BUS caution light
EPCU has reconfigured the main 28 VDC generation system because of a source or fault condition
L or R AC BUS caution light
AC generator not connected to its bus due to a right bus fault condition or the AC generator contractor is open while the generator is operating and the AC generator toggle switch is set to ON
STBY/AUX/MAIN BAT HOT warning light
battery temperature is greater than 71C
