Austrian Federal Railways (BBÖ) class 1082

The 1082.01 was a single experimental electric locomotive built in 1931 that used a rotary converter for continuously variable power control to prevent slipping. The single-phase AC from the overhead line was converted into three-phase AC and then to variable DC. The converter apparatus included an excitation machine, two frequency converters and the actual phase converter. It was around seven meters long and had a cylindrical case, what looked like the boiler of a steam locomotive.

The locomotive had five driving axles, of which the middle three were powered by one DC motor each. The outer two were powered via coupling rods. Additionally, there was one carrying axle on each end. In the end, the BBÖ did not take over this locomotive as test runs showed that it needed constant support from the manufacturer. Essentially, continuously variable power control still needed multiple decades until it became practical thanks to the introduction of solid-state thyristors.