In 1914 the EP 235 was procured as an electric passenger locomotive, which was to become part of a comparison between locomotives with one and two frames. Despite the initially expressed reservations about single-frame locomotives, this machine was able to convince, but the production of the EP 236 to EP 246 did not take place until ten years later.
Originally, the designs envisaged a locomotive with a 1-D-1 wheel arrangement, but the weight of the transformer required an additional axle on one side, which is why the front carrying axle was replaced with a bogie. In order to achieve good curve running ability, the laterally movable bogie was connected to the first coupled axle via a Krauss-Lotter bogie, which was derived from the Krauss-Helmholtz bogie often used in steam locomotives. The rear carrying axle was mounted in a bissel frame and the first and third of the coupled axles were mounted sideways, while the fourth had a weakened wheel flange. This design achieved good running properties and also a level of wear that was within acceptable limits.
The heart of the locomotive was a gigantic electric motor, which was located just above the second and third coupled axle. Its stator had a diameter of 3,600 mm and its rotor 2,700 mm. This is still the largest motor ever used in a locomotive with an hourly and continuous output of 2,200 and 1,650 kW. With a weight of 22 tonnes, the motor was significantly heavier than the transformer, which weighed only nine tonnes. The power was transmitted via connecting rods, which were arranged in a triangular shape below the locomotive body.
Although series production did not materialize for the time being because of the war, the EP 235 met the demands placed on it. These included pulling trains weighing 500 tonnes on the flat at 90 km/h and on two percent still 360 tonnes at 60 km/h. In addition, it was determined that curve radii from 180 meters should be able to be negotiated without excessive wear.
Finally, in 1924, another eleven machines were manufactured, which were very similar to the prototype. Some innovations that had come up in the meantime were implemented. This meant that the motor could be designed with a 240 mm smaller diameter for the same continuous output, which made it 3.3 tonnes lighter. The hourly output was even increased to 2,400 kW. This engine was also used in the ES 51 to ES 57, which were based on the same design.
In use on the Silesian network, the locomotives proved themselves so well that they were even used in front of freight and express trains. Due to their high power and small coupled wheels, they were able to accelerate very well on the winding routes, which made considerable savings in travel time possible. On the 155 km route between Görlitz and Königszelt, between half an hour and a full hour could be saved compared to steam operation.
The prototype was retired in 1927. The remaining locomotives, now designated as E 50 36 to E 50 46, often had to take on replacement work for E 17 and E 210, which put a lot of strain on them and meant a lot of wear and tear. At the end of the Second World War only two of them were operational. They were scrapped in 1956 along with the remaining nine locomotives still in the scrap yard.