AET AET Aircraft Power Systems 3

Question 1

What is the function of a current transformer (CT) in an aircraft AC power system?

Accepted Answer

Provides a proportional low-current signal for metering and protection circuits without direct connection

Answer

Current transformers produce a scaled-down current proportional to the high line current, allowing ammeters and protective relays to measure and monitor generator load safely.

Question 2

What is the role of a voltage regulator in an aircraft alternator/generator system?

Accepted Answer

To maintain constant output voltage despite varying loads and engine speeds

Answer

The voltage regulator senses alternator output voltage and adjusts field current to maintain a constant, preset output voltage regardless of changes in engine speed or electrical load.

Question 3

When troubleshooting an aircraft electrical system and the ammeter shows a discharge indication with the engine running, what is the most likely cause?

Accepted Answer

The alternator is not producing output or is off-line

Answer

A discharge reading on the ammeter with the engine running indicates the battery is supplying the electrical load, which means the alternator has failed or been disconnected.

Question 4

Thermal runaway in a NiCd aircraft battery is dangerous because it can result in:

Accepted Answer

A self-sustaining charging reaction that generates heat, gas, and potential fire

Answer

Thermal runaway occurs when heat from charging increases the battery's ability to accept charge, generating more heat in a feedback loop that can lead to fire, explosion, and toxic gas release.

Question 5

What is the purpose of an overvoltage protection relay in an aircraft electrical system?

Accepted Answer

To disconnect the alternator from the bus if output voltage rises above a safe threshold

Answer

The overvoltage protection relay monitors alternator output and automatically disconnects the alternator from the bus if voltage rises above approximately 31–32V (28V system) to protect sensitive avionics from damage.

(AET) Aircraft Electronics Technician Practice Test

(AET) Aircraft Electronics Technician Practice Test

AET AET Aircraft Power Systems 3