The first locomotive with Kálmán Kandó rod drive to be used under single-phase AC in Hungary was the V50.001 built in 1923. It was based on the FS E.552, but the three-phase power supply had been switched to a motor-generator that converted the single-phase current from the overhead line into a three-phase current with a constant frequency. The first line to be electrified with 16 kV and 50 Hz was the one between Budapest and Hegyeshalom and the V50.001 was tested there.

Of five axles, only the second and fourth one were rigidly mounted in the frames, while the three others had 40 mm of lateral play. The two traction motors transmitted their power over flexible triangular rods onto the central axle and all other axles were driven through connecting rods. Switching the poles of the motors created four continuous speeds up to 66 km/h and liquid resistors running in soda were used for the transition between those fixed speeds. Two pantographs were mounted together in the center of the roof and formed a set of scissors.

First tests showed some deficits like insufficient cooling of the motor-generator, what meant that the locomotive had to be rebuilt. It was ready to run again in 1928. Now the roof had two pantographs at the ends and a central cooling duct for the motor-generator. It could also demonstrate that it was now able to haul a 1,200-tonne freight train for twelve hours without interruptions. In service, it was rated for freight trains up to 1,420 tonnes and express trains up to 500 tonnes. The positive results with the V50 led to the construction of the mixed-traffic V40 and the freight-only V60 from 1932.