Electrics Flashcards
When the Battery Master is selected on, what bus(es) will be powered?
L/R ESS buses + battery bus
how many temp sensors are there per battery?
2
MAIN BATT HOT
Main battery internal temp over 65deg. Turn the charging to this battery off and monitor temp.
If it continues to rise then land immediately
What is the fixed AC system primarily used for?
Avionics and flight instruments
How many inverters need to be operational to power the system?
1
What selections are available for the aux inverter and where is the aux inverter connected to the system?
Primary, off, Secondary.
L MAIN bus
What lights are powered directly by the battery bus?
Dome lights and boarding lights
How many batteries does the aircraft have?
2 24v Nicad batteries in the nose
What buses will have power with the Batt master on and the main battery on and main tie connected?
L/R ESS and L/R MAIN buses
how do we get power to the L MAIN bus on the ground (no engines)?
Main bus tie
What voltage should we see on tthe DC monitor when external power is connected?
28V
Which buses will be powered with DC external power plugged in?
All DC buses
Will external power charge the batteries?
Yes if GPU voltage higher than battery voltage
Will the APU charge the batteries?
Yes if GPU voltage higher than battery voltage
Min voltage for engine start on batteries?
22V
At what voltage does over voltage protection lock out external power?
31.5V
Can external power and the engine DC gens be on line at the same time?
No, External power is sensed by the GCU which automatically turns off the DC gens
If a DC gen fails, will the opposite main bus be powered?
Yes through the main bus tie (bus tie logic)
How are DC gens cooled?
Air cooled
What are the DC gen load limits on the ground and in the air?
- 7 on the Ground
1. 0 in the air
If the Main buses are powered, are the essential buses automatically powered?
Yes, through diodes
Will the AC gens be online wil the props in feather?
No
What do the AC gens provide power to?
The L/R 115VAC buses
If an AC gen failed in flight, would the opposite AC bus be powered?
Yes through the bottom bus tie
Which buses power the TRU’s?
115VAC buses
What buses are directly powered by the TRU’s?
L/R secondary buses
What is the input and output of the TRUs?
In: 3 phase (87Amp per phase) 115V VAC
Out: 28V DC, 200Amp max each, (25-30V dependant on load)
How can a TRU be turned off?
Pull the CB
If one TRU fails, will both secondary buses be powered?
Yes through the secondary horizontal bus tie
If both TRU’s fail, will the SEC buses be powered?
Yes through both main buses (vertical ties)
What is DC logic?
The unit that controls closing of bus ties automatically following a set of perameters (Slaney’s mouse)
What is the priority for DC logic?
Horizontal ties
DC BUS
More than 400Amp draw detected on one of the main buses.
All Central ties inhibited from closing. If this caution persists for 7 seconds, main battery and gen are also disconnected automatically
What is the function of the DC bus reset switch?
To reset the DC BUS fault to check if the fault remains
Loss of both DC generators procedure requires turning off all battery switches. why? what is supplying the power for the DC system? What if one fails?
To prevent over heating the batteies as the TRU’s arent regulated
The TRU’s supply all the DC power,
If one fails, all cockpit power is lost (horizontal tie priority)
What are the TRU load limits?
1.0 in flight and on ground
AC gen limits?
0.33 on Ground (above 10deg) otherwise 1.0
At what voltage are the batteries considered flat?
20V
What is the amp/hr rating of the batteries? how long will we have battery power for in a complete electrical failure?
40A/hr. 30mins guarenteed (51mins really)
How many amps are being drawn from a DC gen at a load rating of 0.7?
210Amps
What are the 2 battery heat sensors connected to?
One to temp gauge, other to BATT HOT warning. both to master warning
What is connected to the Battery bus?
ENG +APU fire ext. activation circuits Fuel and hydraulic shutoff valves Refuel/Defuel shut off valves + refuel panel Dome lights and Boarding lights PA emergency power
What bus does the external power and APU power feed into?
R MAIN (GPU is also L MAIN)
What is the danger of turning on the GPU without the batteries on?
Power spike and damage to equipment
What will happen is the GPU is left plugged in but switched off?
The external power circuit stays connected, green light stays on but massive discharge from batteries (~1.2)
If you have a blown external power CB will starting be available?
Not on external power, the other CB will blow
In the cockpit what instruments are powered by the ESS bus?
CAPT instruments and screens,
Engine instruments,
LDG gear and Flap
NAV1/COM1 (note no FMS)
Where does power for F/O’s instruments come from?
R MAIN (also COM2/NAV2, Antiskid and an FMS)
What temp do the BATT HOT warnings come on at?
65deg
Where is the DC gen on the engine?
Accessory gbox
What does a flashing +ve sign mean on a DC gen readout?
That gen is producing more than 300Amps
What are the functions of the Generator control unit
Controls the start sequence to 63% NH
Regulates voltage to 28V
Fault sensing
1/2 DC GEN
DC gen not connected
1/2 DC GEN HOT
Gen overheat - QRH
What freq do the VAC and FAC buses operate at?
400hz FAC, 200-400 VAC
What inverter powers the CAPT nav gear?
Primary (L ESS)
PRI/SEC/AUX INV
Inverter failure
L/R 26VAC
Bus unpowered
Max amps from GPU?
1500
If the external power is a lower voltage than the batteries what will happen?
The batteries will discharge
What cools the AC gens?
Oil cooled
What are the 115VAC buses primarily used for?
heaters and pumps
1/2 AC GEN HOT
AC gen overheat - QRH
No auto disconnect
1/2 AC GEN
AC gen not producing power
Where are the TRU’s and CB’s located in the AC?
Nose
L/R TRU
TRU failure/not operating
L/R TRU HOT
overheating TRU, manual disconnect
How many ties can the mouse close at once?
2 (horizontal or vertical)
Is it possible to run the entire AC on one AC gen?
yes if both TRU’s operational
BBPU?
bus bar protection unit (disconnects main batt, dc gen and opens ties when DC BUS)