Electrical system overview

Question 1

Electrical Power

Answer 1

Generates:

• Alternating current (AC)
• Direct Current (DC)
• Standby AC and DC Power

Question 2

Primary AC (Alternating Current)

Answer 2

• Primary AC electrical power is supplied by 2-engine-driven integrated generators
• IDG (Integrated Drive Generators)
• The IDGs are lubricated and cooled by a self-contained oil system

Question 3

IDGs (Integrated Drive Generators)

Answer 3

• The IDGs supply power directly to the AC transfer buses
• Each IDG is controlled by a generator circuit breaker
• GCB (Generated Circuit Breaker)

Question 4

AC Transfer busses (part 1)

Answer 4

• Transfer busses are connected by a tie bus and 2 bus tie breakers
• BTB (Bus Transfer Breakers)

Question 5

AC Transfer busses (part 2)

Answer 5

• The AC transfer busses supply power to the remaining AC busses and transformer rectifiers
• TR (Transfer Rectifiers)

Question 6

TR (Transfer Rectifiers)

Answer 6

-The Transfer Rectifiers (TR) are the primary source of power to the DC busses

Question 7

Battery part 1

Answer 7

• The main battery energizes the hot battery and the switched hot battery busses when AC power is not available
• The battery also supplies emergency power for the battery bus and the AC and DC standby busses

Question 8

Auxiliary battery

Answer 8

-The auxiliary battery is used only as emergency power source for the standby power system

Question 9

Battery chargers

Answer 9

• The battery charges maintain the batteries’ charge

- The main battery charger is also the normal source of power for the hot battery and switched hot battery busses

Question 10

APU (Auxiliary Power Unit)

Answer 10

-The APU operates a generator which can supply all necessary electrical loads inflight or on the ground

Question 11

External AC power

Answer 11

• External AC power can also be on the ground

- It is connected to the airplane through a receptacle on the lower right side of the fuselage

Question 12

Rule 1 of operating the 737 electrical system

Answer 12

-AC power source cannot be operated in parallel

• Only 1 source of AC power:
• IDG (Integrated Drive Generator)
• APU generator
• Ground power

Question 13

Rule 2 of operating the 737 electrical system

Answer 13

-If a second power source is connected to a transfer bus. The first source is automatically disconnected

Question 14

Electrical Control panel

Answer 14

• AC and DC metering panel
• The generator drive and standby power panel
• Ground power and bus switching panels

Question 15

Circuit Breakers

Answer 15

• The P6 panel is behind the F/O

- The P18 panel is behind the Captain