Electrical Power AC/DC Systems

Flashcards covering key concepts related to AC and DC electrical power generation, distribution, and protection systems in an aircraft.

What are the main sources of AC power in an aircraft when the engines are running?

Integrated Drive Generators (IDGs)

What is the function of a Constant Speed Drive (CSD) within an IDG?

It converts variable engine speed into a constant generator speed.

How much AC power does each IDG generate?

40 kVA, 115 V, 400 Hz, 3-phase

What controls the IDG?

The Generator Control Unit (GCU)

Where is the IDG selector knob located and what are its normal operating positions?

Overhead control panel; 'AUTO' and 'OFF'

What happens when the IDG selector knob is held in the 'DISC' position for 1 second?

The IDG will mechanically disconnect and can only be reset by maintenance personnel on the ground.

What is the secondary AC power source on the ground and for abnormal operations in flight?

The Auxiliary Power Generator, mounted on the APU.

What provides emergency AC power for the EPGDS in case of sudden loss of AC power in flight?

The Ram Air Turbine (RAT)

Where is the Ram Air Turbine (RAT) installed?

In the right nose section.

How much AC power does the Ram Air Turbine (RAT) generate?

15 kVA, 115 V, 400 Hz, 3-phase

What EICAS warning message illuminates if auto deployment of the RAT fails?

'BATT DISCHARGING'

How can the RAT be deployed manually?

With the RAT lever on the center pedestal.

What converts DC to AC power when the EPGDS is only on battery?

One static inverter, located in the forward E-bay.

What is the input and output for the static inverter?

Input: 28V DC; Output: 115V AC 400Hz

What are the main DC power sources when an AC source powers the aircraft's AC buses?

Three Transformer Rectifier Units (TRUs)

Where are the TRUs located?

TRU1 in Left Integrated Control Center, TRU2 in Right Integrated Control Center, TRU essential in Emergency Integrated Control Center.

What is the input and output for TRUs?

Input: 115V AC, 400Hz; Output: 28V DC, 300Hz

What are the secondary DC power sources?

Two nickel-cadmium batteries (Batt 1 and Batt 2)

What is the primary function of Batt 1 and Batt 2?

To provide APU start and power DC essential loads in case of power loss until the RAT is working.

Where are Battery 1 and Battery 2 located?

Batt 1 in the forward E-bay, Batt 2 in the aft E-bay.

When will any available AC source charge both batteries?

During normal operations.

What is an ICC (Integrated Control Center)?

An electrical device that provides power distribution and protection for the airplane's electrical loads.

How many ICCs are installed and where are they located?

Four ICCs: Left & Right ICC in mid E-bay, Emergency ICC in forward E-bay, Auxiliary ICC in aft E-bay.

What components are incorporated into each ICC?

AC & DC buses, thermal circuit breakers (CB), and Line Replaceable Modules.

Can thermal circuit breakers in the ICC be reset in flight?

No, they are remote and can only be reset on the ground by maintenance personnel.

What is the function of the Secondary Power Distribution Assembly (SPDA)?

It is an electrical load management and power distribution device that distributes power from ICCs to several aircraft systems.

How many SPDAs are installed and where are they located?

Two SPDAs: one in the forward bay and one in the mid bay.

What type of circuit breakers does the SPDA primarily use?

Electronic remote circuit breakers.

How can electronic circuit breakers in the SPDA be monitored and reset?

Via the MCDU in the cockpit, with an EICAS advisory message 'REMOTE CB TRIP' if triggered.

What are the three levels of built-in tests for the electrical system units?

Continuous built-in test, Fault initiated test, and Initiated test.