200 electrical system

Question 1

What is the voltage of the AC and DC system?

Answer 1

115 V AC and 28 V DC

Question 2

What are the sources of AC electrical power for the aircraft? (hint: there are five)

Answer 2

Primary sources are 
2 engine driven integrated Drive generators
1 APU generator
Air driven generator (ADG)
Ground power

Question 3

What provides power if there is a total loss of AC electrical power in-flight?

Answer 3

ADG is deployed on the forward right side of the fuselage

Question 4

What are the sources of DC electrical power? (hint: there are eight)

Answer 4

5 TRUs - transformer rectifier units
2 NiCad batteries
28 V external power

Question 5

How many circuit breaker panels are there and where they located?

Answer 5

There are six circuit breaker panels for on the flight deck, One in the aft equipment bay and one at the flight attendants station.

Question 6

What type of power do the IDGs supply?

Answer 6

115 V AC 400 Hz 3-phase electrical power.

Question 7

Does the IDG rpm very with engine RPM?

Answer 7

No, the generator must turn at a constant RPM to produce a steady 400 Hz the constant speed drive (CSD) unit accomplishes this task.

Question 8

How does the CSD accomplish a constant RPM?

Answer 8

The CSD is a hydromechanical unit and uses an integral oil system to drive the generator at a constant RPM. The CSD is driven by the engine assessory gearbox, which turns at a variable speed based on engine speed

Question 9

What does the FAULT light in the IDG switch light indicate?

Answer 9

HOT LOP
This light will illuminate with the IDG oil overheats or oil pressure drops below limits. This fault light will also illuminate and IDG caution message on the EICAS.

Question 10

What are the ways that the IDG can disconnect from the engine gearbox?

Answer 10

By pressing the associated IDG DISC switch
When CSD internal temperature raises to a certain temperature the IDG will disconnect.
In over torque condition of the CSD will cause the shearing of the IDG driveshaft.

Question 11

What monitors the generator system?

Answer 11

Each generator has a generator control unit GCU that controls and monitors the related generator system. The GCU provides protection and voltage regulation for the associated generator.

Question 12

What buses are powered when external AC power is connected and the green AVAIL switch light on the external services panel is pressed?

Answer 12

The utility and service buses will be powered.

Question 13

How many AC buses does the electrical system have?

Answer 13

6 buses they are:
BUS 1
–UTIL BUS 1
–ESS BUS

BUS2

• -UTIL BUS 2
• -SERV BUS

Question 14

What happens when AC bus 1 has a short and takes generator 1 off-line?

Answer 14

The auto transfer inhibit Will stop the transfer and a amber FAIL light in the AUTO XFER switch will illuminate. The FAIL means it has done its job.