Electrical

Question 0

What components make up the AC Electrical System?

Answer 0

2 engine driven 115vAC Generators

Question 1

What components make up the DC Electrical System?

Answer 1

3 24vDC, 40 amp NiCad batteries
2 28vDC, 400 amp Engine Driven Starter Generators
2 28vDC, 300 amp Transformer-Rectifiers
1 28vDC, 400 amp APU DC Generator

7 DC Busses:
Hot Battery Bus
Left and Right Main Busses
Left and Right Secondary Busses
Left and Right Essential Busses

Question 2

Where are the Main, Aux and Standby Batteries are located?

Answer 2

Main: Lower left side of the nose, forward
Auxiliary: Lower left side of the nose, aft
Standby: Upper left side of the nose

Question 3

Which batteries assist with engine starts?

Answer 3

Only the Main and Aux batteries

Question 4

In an emergency, all 3 batteries power the Essential DC Busses providing emergency power for approximately _______?

Answer 4

45 minutes

Question 5

What does the Standby battery do?

Answer 5

Powers the Hot Battery Bus

Question 6

What is the max battery load meter reading for starting an engine?

Answer 6

Below 0.4 on the MFD Electrical Page

Question 7

What does the Battery Master Switch do?

Answer 7

Directly connects all 3 batteries to the Essential DC busses. Independent of the EPCU
Powered by a direct lead from the Standby Battery

Question 8

What does the Main Battery Switch do?

Answer 8

Directly connects the Main Battery to the Right Main Bus for two-way power flow.

Question 9

What does the AUX Battery Switch do?

Answer 9

Connects the Aux Battery to the Left Main Bus for two-way power flow.

Question 10

What does the STBY Battery Switch do?

Answer 10

Connects the Standby Battery to the Left Main Bus for charging only

Question 11

What are the temperatures and colors associated with the batteries on the MFD electrical page?

Answer 11

White = Normal
Amber = 50°- 65°C
Red = Greater than 65°C (\_\_\_\_\_ BATT HOT and MASTER WARNING)

Question 12

Where is the DC External Power receptacle and where does it connect to the electrical system?

Answer 12

Located on the forward left side of the nose and connects to the Left Main DC Bus.

Question 13

When DC External Power is connected, can the APU DC Gen and/or DC GEN 1 & 2 run in tandem?

Answer 13

No. DC External Power prevents DC GEN 1 & 2 and the APU DC GEN from coming online while it is selected on.

Question 14

Once the engines are started and the DC External Power is disconnected, how are the secondary busses powered prior to the AC GENS and TRU’s coming online?

Answer 14

Through the Main-Secondary Bus Ties

Question 15

The EPCU provides automatic protection against DC External power malfunctions and will automatically take the DC External Power offline if the voltage goes over ____ or below ____.

Answer 15

Over 31 volts or below 22 volts

Question 16

Where are the Engine Driven DC Starter Generators located and how are they cooled?

Answer 16

The DC Starter Generators are located on the engine accessory gearbox and are air cooled.

Question 17

When does the Generator Control Unit switch the DC GEN from starter mode to generator mode?

Answer 17

After engine start and approximately 50% Nh the GCU will change the DC GEN from starter to generator and begin to power the associated Main Bus.

Question 18

Will the EPCU automatically take a DC GEN offline if it overheats?

Answer 18

No. If the #1 DC GEN HOT or #2 DC GEN HOT Caution light is illuminated the QRH will direct the flight crew to turn off the associated generator. The main bus tie will close allowing one generator to power both main busses.

Question 19

What do the Transformer Rectifier Units do and what do they power?

Answer 19

Convert 115vAC power from the AC Generators to 28vDC power for the secondary busses.

Question 20

Where are the TRU’s located? How are they cooled?

Answer 20

Located in the upper right nose section and are air cooled.

Question 21

Is there a switch to turn off the TRU’s?

Answer 21

No, only a circuit breaker on the 115 vAC panel located behind the co-pilot

Question 22

Can the APU DC Generator provide power in parallel with the engine driven DC generators? Where does the APU Generator connect to?

Answer 22

Yes, on the ground the APU DC Generator can provide power to all of the main, secondary and essential busses by connecting to the right main bus and powering the others through the bus ties.

Question 23

What happens if the EPCU detects a bus failure or fault?

Answer 23

It will automatically take that bus offline and reconfigure the bus ties to power the remaining busses.

Question 24

When will the EPCU begin load shedding with multiple failures?

Answer 24

If there are two TRU failures along with a single DC GEN failure the EPCU will begin to shed non essential electrical loads.

Question 25

What failures would lead to an electrical emergency and what does the EPCU do in that case?

Answer 25

If two DC GENs were to fail along with a single TRU then the EPCU will remove the ties from the batteries to the main busses, powering only the essential busses for approximately 45 minutes. The remaining TRU will also power the secondary busses.

Question 26

Where are the 115vAC generators located? How are they cooled? What busses do they power?

Answer 26

The engine driven, oil cooled generators are mounted on the prop reduction gearbox. Each generator powers its respective variable AC BUS or if one fails, a single AC GEN can power the other bus and entire DC system through the bus cross tie (as long as the TRU’s are operational)

Question 27

What components on the airplane are AC powered?

Answer 27

Windshield heating elements
Ice detector probes
#1 & #2 Pitot static tubes
AOA vanes
Engine Inlet Heating elements
Standby Hydraulic Pump
Auxiliary Fuel Pumps
Propeller de-icing elements
TRUs
Galley Power