Electrical Flashcards
The AC system is comprised of:
Two IDG's One APU One Inverter One Ram Air Turbine - RAT One AC external power unit
The DC system is comprised of:
Two NiCd batteries
Three TRUs - Transformer Rectifier Units
One DC external power unit
On the AC Electric Panel, the IDG 1/2 switch in the OFF position does what?
Opens the IDG contactor isolating the IDG from the respective AC Bus
How long must one hold the IDG 1/2 in the DISC positon
Must be held in this position for one second to mechanically disconnect the IDG
What does the AC BUS TIES switch do in the 1 OPEN position?
Opens the Bus Tie Contactor - BTC 1 - segregating AC BUS 1 from AC BUS 2
BATTERY 2 supplies power to … ?
HOT BATT BUS 2
In the ON position, BATT 1 is connected to.. ?
the DC ESS BUS 1
BATTERY icons in GREEN
Battery voltages greater than 18 V
BATTERY icons in WHITE
Battery voltages less than 18 V
What is the meaning of IDG 1/2 OIL EICAS Msg?
IDG pressure drops below 140 psi
or
IDG oil temperature reaches 168 deg C
Do not hold the IDG 1/2 knob in the DISC position for longer than.. ?
3 seconds
The IDG will automatically disconnect when… ?
when manual disconnection is not performed with the oil temperature reaching 185.6 deg C
Pushing the AC GPU button connects…
The external power to the AC BUS TIE
The RAT - Ram Air Turbine produces… ?
15 kVa, 115 V AC, 400 Hz
The RAT is deployed whenever… ?
AC power sources are not powering AC buses
How long does it take for the RAT to supply power to the AC ESS BUS
8 seconds
What does the RAT power?
supplies power to the AC ESS BUS
If it takes 8 seconds for the RAT to power the AC ESS BUS, what is the design to prevent total loss of power?
The RAT powers the AC ESS BUS which powers the ESS TRU which powers DC ESS BUSES. To avoid total loss of power for the 8 seconds it takes to power, dedicated standby battery is used as backup power to the DC ESS BUSES and the STANDBY AC BUS
How are primary flight control tasks maintained in the event of loss of electrical power?
RAT drives the ACMP 3A
What is NBPT
No Break Power Transfer
What does the NBPT do?
The No Break Power Transfer allows the momentary paralleling between two AC power sources: The IDG’s, GPU and APU generator in any combination
On the DC Power Panel, what does the DC BUS TIES toggle switch do
Opens both essential tie contactors and a DC tie contactor
The RAT powers what?
AC ESS BUS when AC bus 1 and 2 are not powered
What is the minimum battery voltage
22.5 Volts without action
below that and the battery needs to be warmed up per the SOPM
21.0 limit below which maintenance needs to be called out.
Generators are rated to
40 KVA
the RAT generator is rated to…
15kVa
How long does it take the RAT to power the AC ESS BUS
8 seconds
When is the RAT deployed
When both AC Bus 1 and 2 are not powered
The LED light next to the IDG switches indicate what?
Which IDG needs to be disconnected due to a drop in oil pressure below 25 psi and / or a oil temperature reaches 168 deg C
Automatic IDG disconnect happens when the oil temperature reaches …
186 deg C
During APU start what happens?
BATT 2 is isolated from the network and used to power the APU START BUS exclusively