Electrical

Question 1

What causes STANDBY POWER light to illuminate?

Answer 1

AC standby bus unpowered

Question 2

Standby power system main components (7)

Answer 2

Battery
Static Inverter
AC standby bus 
DC standby bus, 
Battery bus, 
Hot battery bus 
Switched hot battery bus

Question 3

Standby Power Switch in AUTO / AC transfer buses powered

in flight or on ground

Answer 3

AC Standby Bus is powered by AC transfer bus 1

DC standby bus is powered by DC bus 1

Question 4

Standby Power Switch in AUTO / loss of all AC power

in flight or on ground

Answer 4

(in flight)
AC Standby bus is powered by battery via static inverter
DC standby bus is powered by battery bus

(on ground)
AC & DC Standby bus are both powered by the battery bus

Question 5

Standby Power Switch OFF

Answer 5

STBY POWER OFF light illuminates

AC Standby,static inverter, and DC standby bus are not powered

Question 6

Standby Power Switch to BAT

Answer 6

AC Standby bus is powered by battery via static inverter

DC standby bus is powered by battery bus

Question 7

Primary electric power is provided by?

Answer 7

2 engine driven generators and an APU which each supply 3 phase, 115v, 400hz, AC power.

Question 8

What supplies primary DC power

Answer 8

3 TRUs and a 24v battery supply 28v DC power

Question 9

Battery Power

Answer 9

24v nickel cadmium battery can supply standby power for 30 min. Voltage range is 22-30v

Question 10

Generator Drive Unit (GDU)

Answer 10

Provides constant frequency through normal operating range of the engine. Generator is coupled directly to the engine. Each GDU has self contained with its own oil, cooler, instrumentation and disconnect device.

Question 11

AC power system main components

Answer 11

Each AC system consists of a 
gen bus, 
main bus, 
transfer bus, 
left side also includes ground service bus.

Question 12

What supplies power to AC standby system?

Answer 12

AC transfer bus 1

Question 13

Bus transfer system

Answer 13

Gen buses supply heavy electrical loads
transfer buses carry essential electrical loads
main buses carry non essential loads

If a gen trips off, Gen bus and main bus will not be powered. Each transfer bus has a transfer relay which automatically selects opposite gen bus as its power source. (switch must be in auto)

Question 14

TRU’s

Answer 14

Convert 115vac to 28 vdc.

TRU1 and 2 powered by DC bus 1 and 2

TRU3 powers the battery bus and is backup for TRU 1/2

Question 15

TR3 disconnect relay automatically opens for what?

Answer 15

Isolates DC bus 1 from DC bus 2 at glideslope capture during FD or AP ILS preventing single failure from affecting both NAV receivers and FCCs.

Question 16

DC busses powered from battery following loss of both generators?

Answer 16

battery bus /
DC standby bus /
hot battery bus /
switched hot battery bus

Question 17

Battery charger powered by?

Answer 17

AC ground service bus

Question 18

purpose of residual volts switch?

Answer 18

With gen switch OFF residual voltage is shown on voltmeter.