Electrical Flashcards
What is the primary source of AC electrical power?
Two engine driven integrated drive generators (IDG).
What is the nominal electrical rating of the engine driven integrated drive generators (IDG)?
115 volt ac, 400 hz three-phase electrical power with a nominal rating of 40 kva to an altitude of 41,000 feet.
What is the function of the integrated drive mechanism?
The integrated drive is a hydromechanical device that is driven by the variable-speed engine accessory gearbox which uses an integral oil system to drive the generator at a constant speed.
What is the function of the oil within the integrated drive unit?
Oil is used within the IDG unit as a lubricant, for generator cooling and as a hydraulic fluid for the csd speed adaptation. The oil system is monitored for faults and indicated to the pilots by EICAS messages as well as electrical power control panel (EPCP) switchlights.
What does the amber “FAULT” illumination indicate in the IDG switchlight located on the Electrical Power Control Panel (EPCP)?
The IDG oil has overheated, or the oil pressure has dropped below predetermined limits.
What does an illuminated IDG “DISC” switchlight indicate to the pilots?
An electrical solenoid has been energized inside the IDG housing that caused the integrated drive gear (input shaft) to retract from the engine accessory gearbox. The IDG stops rotating after disconnect.
When can IDG be reset after being disconnected via the IDG switchlight located on the Electrical Power Control Panel (EPCP)?
The drive can only be reconnected on the ground after the engine is shut down.
What will occur if the IDG electrical disconnect feature fails?
Mechanical disconnect of the IDG will occur when the internal temperature exceeds a predetermined limit or by shearing of the IDG drive shaft when an overtorque condition is detected. It prevents damage to the accessory gearbox due to IDG failure.
Where can the output parameters of the IDG be monitored in the cockpit?
The output of the IDGs can be monitored via the EICAS AC synoptic page. Output indications are provided in a parameter block at the bottom of the display.
What is the primary function of the Auxiliary Power Unit (APU) generator?
To provide an electrical power to the aircraft buses during ground operations with the engines off. It can also be used to power the buses in flight should an engine generator fail.
What is the nominal electrical rating of the APU generator?
115 volt ac, 400 hz three-phase electrical power with a nominal rating of 40 kva to an altitude of 41,000 feet.
How is the APU AC generator constant rpm maintained?
The APU operates at a constant speed so there is no requirement for a constant speed drive (CSD) interface between the APU generator and the AC generator.
When is the APU generator capable of supplying electrical power?
After a minimum rotor speed of 99% for 2 seconds or longer.
What is the function of the external power system?
The external power system is used to connect AC electrical power from a ground source.
What is the location of the AC external power receptacle?
The forward right side of the aircraft below the external services panel and above the right nose gear door.
What is the location of the external services panel?
The forward right side of the aircraft nose above the AC external power receptacle.
How is the status of the AC external power monitored from the cockpit?
The status of the AC external power source is displayed on the EICAS AC electrical synoptic page and the AC AVAIL/IN USE switchlight located on the Electrical Power Control Panel (EPCP).
How is the status of the AC external power monitored from outside the aircraft?
The status of the AC external power source can be verified via the AC AVAIL/IN USE switchlight located on the external services panel.
What has priority, internal or external power?
Internal power
What is the electrical requirements of the AC external power?
Three-phase electrical power 115/200 volt 400 hz.
What does the green illuminated “AC AVAIL” button located on the Electrical Power Control Panel (EPCP) indicate in the cockpit & on the external services panel?
The external power is connected to the external receptacle and the power is acceptable (115/200v 400hz) to the aircraft.
What does the white “IN USE” illumination of the AC external power button located on the Electrical Power Control Panel (EPCP) signify?
The “IN USE” portion of the switchlight will illuminate after the pushbutton is depressed and the AC external power source is supplying the aircraft electrical system.