What is the function of a transformer-rectifier unit in some aircraft?

What is the function of a transformer-rectifier unit in some aircraft?

• A. It supplies alternating current to the bus.
• B. It converts DC to AC.
• C. It converts AC power to DC and regulates it to supply DC loads such as avionics and instruments.
• D. It stores energy for peak demand.

Answer: (C)

In aircraft electrical systems, you often have AC power available from generators, and many loads—like avionics and instruments—need stable DC power. A transformer-rectifier unit takes that AC input, rectifies it to DC, and then regulates the output to a steady DC voltage suitable for the DC buses. This means it provides clean, consistent DC power (often around 28 V) to the DC loads and can supply the necessary current while keeping voltage within limits. That’s why the correct description is that it converts AC power to DC and regulates it to supply DC loads. It doesn’t supply AC to the bus, nor convert DC to AC, nor store energy for peak demand (that’s the role of other components like inverters or batteries).

In aircraft electrical systems, you often have AC power available from generators, and many loads—like avionics and instruments—need stable DC power. A transformer-rectifier unit takes that AC input, rectifies it to DC, and then regulates the output to a steady DC voltage suitable for the DC buses. This means it provides clean, consistent DC power (often around 28 V) to the DC loads and can supply the necessary current while keeping voltage within limits.

That’s why the correct description is that it converts AC power to DC and regulates it to supply DC loads. It doesn’t supply AC to the bus, nor convert DC to AC, nor store energy for peak demand (that’s the role of other components like inverters or batteries).