Electrical Flashcards
Conditions for auto transfer
PWR selector on BATT
One MAIN GEN ON
MAIN GEN contactors open
Indication of auto transfer
“6 pack” lights on the electrical panel
Observer light illuminates
What checklist to use in auto transfer
MAIN GEN failure
What charges the main battery in auto transfer
AUX GEN >70Np
Can APU be started in auto transfer
No because central bus is isolated. Must take out of auto transfer before APU start
TRNSFER FAIL light will indicate
AUX Bus failed to transfer to EDC’s. Electrical system is powered by battery only
How is backup battery being charged
EDC 2
Backup battery powers standby gyro when
EDC 1 drops below 19v
How long can backup battery support standby gyro
30 min
What must be on for inverters to work
Radio masters
If you lose 115vac on inverter 1 what happens to the inverter, if 26vac
Inverter 2 will pick up inverter 1 automatically in the event of 115vac, 26vac must be switched manually
GPU amps and volts required
24 volts, 1600amps min 1800 recommended
Can GPU voltage be read in the cockpit
No only amps
Can GPU charge the main battery
No
What is on the hot battery bus
- Auto transfer
- Clock/Chronograph
- Coutesy lights
- DC indication 1 & 2
- Fire extinguisher left and right
- Forward entry door
- Fuel shutoff valve left and right
- Hydraulic shutoff valve blue and green
If Emergency Transfer happens and APU is available can it be used to power systems
Yes, the system should be placed into normal mode prior to an air start of the APU
How do you prevent a reset to normal operation after emergency transfer
Emergency mode must be selected prior to turning off both generators
Is the battery connected to the hot battery bus
Yes during normal operations the power source that powers central DC bus, powers the hot battery bus and charges the battery
Is there any protection for overvoltage while on GPU
Yes, an overvoltage relay protects the central DC bus if external power exceeds 32VDC
When can APU gen provide electrical power to aircraft
95% RPM
When does the generator switches from starter to generator
50% Nh
How many volts are the inverters
28VDC converted to 115AC and 26AC
What generators is EDC busses connected to normally
Right generator
If one EDC fail how can you tell which on failed
Tq and T6 gauges
EDCI 1 # 1Engine
EDC 2 # 2Engine
When does AUX generator turn on
Np 70%
What is the EDC
The emergency DC, it contains all the essential equipment because it is always powered
What is the EDC
The emergency DC, it contains all the essential equipment because it is always powered
Functions of GCU
- Initiates starting cycle
- Cancels starting cycle at 50% Nh
- Regulates generator output
- Overvoltage protection
- Overcurrent protection
- Reverse current protection
- Generator field over exiting protection
- Load sharing
Functions of AUX GCU
- At 70% Np connects generator to AUX DC BUS and disconnects DC BUS 3 form DC BUS 2 and connects it to AUX DC BUS
- Voltage regulation
- Overvoltage protection
- Undervoltage protection
- Overcurrent protection
- Generator field over exiting protection
- Load sharing
- Underspeed protection when Np drops bellow 70%
Generator Specification
MAIN GEN = 28VDC 400A (600A during start)
AUS GEN = 28VDC 150A
APU = 28VDC 400A
Battery Specification
MAIN BATT = 24VDC 36A/H Nick-cad
BACKUP BATT = 24VDC 5A/H sealed led acid
The EMB 120 Electrical system supplies
28VDC and 26/115 AC
The EMB 120 has how many generators
5
The EMB120 has how many batteries
2
When using GPU can APU gen be used
No power source priority
During the engine start phase, the starter generator is powered from
Central DC bus
Can you start the engines in electrical transfer mode
No, no supply to Central DC BUS
The main generators are connected to the electrical system by
Main generator contactors
The EMB 120 has how many inverters
2
The No 1 and 2 inverters is powered through
DC Bus 1 inverter 2
DC Bus 2 inverter 1
With total generator failure the main battery will last
Approximately 30 minutes
APU generator is identical to
Main generator
Are the AUX generator identical to Main GEN
No
The APU generator may be used with the battery for engine start
True
The primary reason for Auto transfer
Both main generator failure
During normal operation AUX GEN power
DC bus 3 and RB DC 3
The back up battery will automatically supply electrical power to the standby attitude indicator when
EDC 1 drops below 19V
The aircraft batteries located
Left nose compartment
During engine start the primary purpose of the back up battery is
To prevent transients affecting certain instruments
In total electrical emergency the backup battery’s primary purpose is
To power the standby gyro only
