Practice Problems

1. Answer the following questions about the devices shown in the following table

Device	Current	Voltage
A	3 A rms	190 V rms
B	8 A rms	190 V rms
C	3 A rms	190 V rms
X	10 A rms	40 V rms
Y	4 A rms	40 V rms
Z	5 A rms	40 V rms

a. Draw the block diagram to represent this set of devices

b. Label circuit breaker locations and values

c. Calculate total power supplied

2. Calculate the following for the power distribution system below:

   a. turns ratio of the transformer

   b. circuit breaker values for circuit breakers A, B, C

   c. Power the source produces

3. T / F Buses work by delivering power to devices connected in series.

4. T / F A circuit breaker works the same as a fuse in that it opens when current exceeds the circuit breaker’s rating.

5. The electrical system for a small reconnaissance aircraft is shown below. The aircraft has two busses, one at 160 V~RMS~ and one at 50 V~RMS~, powered by a 160 V~RMS~ alternator.

1. What transformer turns ratio is required to drive the 50 V~RMS~ bus?

2. Given the following table of required currents, what circuit breaker ratings would you choose for the circuit breakers labeled A, B, C, and D?

Equipment	current (A rms)
Flaps	2.5
Avionics	4
Navigation	6
Comm	3.5
Camera	4.5

6. The electrical system for a fighter is shown below. The aircraft has two busses, one at 80 V~RMS~ and one at 20 V~RMS~, powered by a 115-V~RMS~ alternator.

a. What transformer turns ratios are required to drive the two buses?

b. Given the following table of required currents, how much power must the alternator provide?

Equipment (A rms)	Current
Flaps	5
Landing Gear	8
Radar	4
Computer	2
IRS	5

7. The electrical system for a fighter is shown below. The aircraft has two busses, one at 80 V~RMS~ and one at 20 V~RMS~, powered by a 115-V~RMS~ alternator.

a. What transformer turns ratios are required to drive the two buses?

b. Given the following table of required currents, how much power must the alternator provide?

Equipment (A rms)	Current
Flaps	5
Landing Gear	8
Radar	4
Computer	2
IRS	5

8. An aircraft requires a 205-V~RMS~ bus and a 32-V~DC~ bus as shown below. Calculate the turns ratio of the transformer and the circuit breaker values for circuit breakers A and B. The Comm equipment draws 4 A of current and the Camera draws 5 A. The efficiency of the AC-to-DC Converter is 80%.

9. You have previously designed everything shaded gray in the block diagram below for an end user. Now, your user has decided to give you a new requirement to drive a 5 V DC bus for the satellite’s computer and camera. Since you really don’t want to have to start all over, you decided to retrofit your system as below. Is this a good design? Why or why not?

10. The electrical distribution system shown below is for a building’s security system. Each component is vital to some aspect of the security of the complex. How many breakers would you add to this diagram? Where would you put them?