What is the primary function of a traction transformer?

The primary function of a traction transformer is to step down high voltage from the power supply. In railway systems, traction transformers play a crucial role in delivering the appropriate voltage to the traction motors that drive the trains. These transformers take the high-voltage electrical supply, which is often necessary for efficient transmission over large distances, and convert it to a lower voltage suitable for the electric traction system. This stepping down process ensures the electrical energy is safely and effectively utilized to power the train's motors, facilitating movement.

While the other options might relate to aspects of train operation, they do not describe the function of the traction transformer accurately. The conversion of mechanical energy into electrical energy pertains to generators rather than transformers. Maintaining the train's speed is a function of the control systems and motors, rather than the transformer itself. Improving air conditioning is unrelated to the electrical function of the traction transformer, which focuses solely on voltage transformation and electrical distribution. Therefore, stepping down high voltage from the power supply is indeed the correct and primary function of a traction transformer.