What is the primary function of a transformer-rectifier unit (TRU) in aircraft electrical systems?

What is the primary function of a transformer-rectifier unit (TRU) in aircraft electrical systems?

• A. It converts AC to DC and provides a suitable DC voltage for distribution.
• B. It stores energy for engine starting.
• C. It regulates the generator output.
• D. It supplies AC power for avionics.

Answer: (A)

The main idea is that a transformer-rectifier unit converts AC power into DC power and provides the proper DC voltage for distribution. In aircraft electrical systems, generators produce AC, but most equipment runs on DC, so the TRU uses a transformer to adjust the AC voltage and a rectifier to turn it into DC. The output is then filtered and regulated to a stable voltage (commonly around 28 V DC) and fed to the DC distribution buses. This isn’t about storing energy—that’s the job of batteries or other storage devices. It isn’t about regulating the generator’s output—that’s handled by the generator’s own voltage regulator. And it doesn’t supply AC power for avionics—avionics typically operate on DC, provided by the TRU’s DC output.

The main idea is that a transformer-rectifier unit converts AC power into DC power and provides the proper DC voltage for distribution. In aircraft electrical systems, generators produce AC, but most equipment runs on DC, so the TRU uses a transformer to adjust the AC voltage and a rectifier to turn it into DC. The output is then filtered and regulated to a stable voltage (commonly around 28 V DC) and fed to the DC distribution buses.

This isn’t about storing energy—that’s the job of batteries or other storage devices. It isn’t about regulating the generator’s output—that’s handled by the generator’s own voltage regulator. And it doesn’t supply AC power for avionics—avionics typically operate on DC, provided by the TRU’s DC output.