Operate Electrical System Flashcards
What are minimum voltage for Batt 1 and Batt 2 during the safety and power-up checklist?
-22.5 V
-between 21 and 22.5 perform recharging procedure
-below 21 call maintenance
Understand AC Power Priority (Onside, Inside, Outside, Cross-side)
Because there is a potential for 4 AC power sources during normal operations, the term “Power Priority” is used to discuss the order, or ranking, that AC Bus 1 and AC Bus 2 use when selecting a source of power.
Both AC Bus 1 and AC Bus 2 determine their own source independently.
Source priority for powering AC Bus 1 and AC Bus 2 is:
1. Respective IDG. (“Onside”)
2. APU generator. (“Inside”)
3. AC GPU. (“Outside”)
4. Opposite IDG. (“Cross-side”)
IDG= Integrated Driven Generator
What are two main components on the DC HOT BAT BUS 1 and 2 that we, as pilots, care about?
Engine 1 and 2 Fire Extinguishing and Panel Refuel
What type(s) of circuit breakers does the E175 have? How do I access them?
There are thermal and electronic circuit breakers
Some thermal CBs are located in the cockpit on cockpit sidewall panels, non-remote, visually checked by crew. Others, remote, are in the electronic bays (ICCs) and must be checked through the MCDU.
Electronic CBs are located in the electronics bays (SPDAs) and are considered remote CBs. These must be checked in the MCDU.
Briefly explain the purpose of the RAT
Supplies AC power in emergencies
The Ram Air Turbine (RAT) is an AC electrical device installed in the airplane nose section, which converts the kinetic energy of airflow across the turbine into AC power.
In case of total AC power loss in flight, the RAT should automatically deploy and provide AC power for systems essential to the safe operation of the aircraft
What EICAS message would indicate the RAT has NOT deployed during an electrical emergency?
Batt Discharge
What AC Busses are energized during an electrical emergency before the RAT deploys? After the RAT deploys?
STBY AC bus
* DC essential bus
AC essential bus
What items are on the AC STBY BUS?
Engine 1 Exciter 1A
Engine 2 Exciter 2A
What items are on the AC ESS BUS?
AC Fuel Pump 2A
ACMP 3A
SF-ACE 1 Flap CH 1 AC Feed
SF-ACE 2 Slat CH 2 AC Feed
What purpose does an Inverter serve?
The static inverter (AC/DC inverter) converts 28 V DC power from batteries to 115 V AC power to supply the STANDBY AC BUS when an AC power source is not available
What purposes does a Transformer Rectifier Unit (TRU) serve?
TRUs convert AC power into DC power.
Each TRU works in isolation. If one fails, the DC Busses will be powered by the remaining TRUs (as long as the DC BUS TIES toggle switch is selected to AUTO).
Three TRUs convert 115 VAC power into VDC.
TRU 1 provides DC power to DC Bus 1, DC ESS BUS 1, DC GND SVC BUS, HOT BATT BUS 1 and battery #1 charging.
TRU 2 provides DC power to DC BUS 2, DC ESS BUS 2, HOT BATT BUS 2 and battery #2 charging.
TRU ESS provides DC powr to DC ESS BUS 3.
What is the difference between OFF and DISC on either IDG Selector?
Auto: allows automatic operation of the electrical system
OFF: opens the IDG contactor isolating the IDG from the respective AC Bus to trip the IDG offline
DISC: Must be held in this position for one second to mechanically disconnect the IDG. Mechanically disconnect the IDG (must be held in this position for at least 1 but no more than 3 seconds). A reset by maintenance is required for a mechanical disconnect of an IDG.
What, operationally, is powered even while the batteries are off?
Hot Battery Buses are always powered, regardless of battery switch position. Fueling panel is on the hot bus which allows fueling and defueling even while the airplane is powered down.
What will cause the RAT to deploy automatically? What speed is needed to ensure the RAT continues to provide electrical power?
Whenever AC power sources are not powering the AC buses in flight, the RAT is automatically deployed and after 8 seconds, supplies power to the AC ESS BUS.
Minimum 150 KIAS to get the RAT spinning
Minimum 130 KIAS to keep RAT spinning
RAT stays attached to AC ESS BUS - even if we get normal AC power re-established
Flaps 3 landing
