Electrical

Question 1

What are the sources of DC power?

Answer 1

• Main battery
• Main battery charger
• Three Transformer Rectifier (TR) Units

Question 2

What happens when an IDG is decoupled?

Answer 2

The splined IDG drive shaft will retract out of the gearbox for complete drive decoupling from engine rotation

Question 3

What causes the illumination of the DRIVE light?

Answer 3

• engine shutdown
• IDG mechanical failure
• IDG disconnected by activation of the DISCONNECT switch
• IDG auto-decouple due to high oil temperature

Question 4

When is the GRD POWER AVAILABLE light illuminated?

Answer 4

when the external power cord is connected to the aircraft and the power is checked to be within tolerances and available for connection

Question 5

What are the basic principles of operation of the 737 electrical system?

Answer 5

There are two principles to AC power distribution:
* There is no paralleling of AC power sources
* The source of power being connected to a transfer bus automatically disconnects an
existing source

Question 6

How is the AC standby bus normally powered?

Answer 6

By transfer bus 1

Question 7

What is indicated by a GEN OFF BUS light?

Answer 7

illuminate any time an IDG is not supplying power to the transfer bus

Question 8

Is it possible to power one AC transfer bus with external power and the other AC transfer
bus with APU power?

Answer 8

No