Following the electrification of the suburban railway in Warsaw, there was a need for new trains to operate on them. On August 2, 1933, an agreement was reached with British companies to supply electrical equipment for the future units. The chief designer of the mechanical parts of the locomotive was T. Owczarek. A prototype unit was produced in 1935 by
Lilpop, Rau and Loewenstein and
H. Cegielski. The electrical equipment was installed under the supervision of English specialists. The work on first units started in July 1936 and one was presented to the public during an exhibition in August 1936 at
Pole Mokotowskie in Warsaw. The first train to enter revenue service ran on December 15, 1936. By the end of 1937 the
Polish State Railways (PKP) had 60 units in service. A further 16 units were ordered and built by 1939. The units were marked with the PKP service designation of ECmx (E: electric, C: third class, m: motor car with pantograph, x: four axle) and fleet numbers from 91 001 to 91 076. The trailer carriages were designated EBCbdxx and driving cars received EBCbdsxx, with numbers from 92 001 to 92 076. The units consisted of three carriages: a motor car, a trailer and a non-powered control car, permanently coupled in operation and could only be separated in a workshop environment. The three-car units were equipped for
multiple working and with automatic
Scharfenberg couplers, up to three units (i.e. trains consisting of six or nine cars) could be coupled. The use of driver's cabs at both ends meant that the units could travel both ways without having to be turned around. The motor car was equipped with electrical equipment (3 kV and 110 V) housed in a special compartment, located in the front of the car, adjacent to the driver's cab. The low voltage from a
motor-generator set was used to supply auxiliary power and charge the batteries. The trailer and driving trailer had
Jacobs bogie, thanks to this the weight of the unit was reduced. The current was collected from an
overhead line by one of two
pantographs (the rear one), which was raised based on the direction of travel, apart from times when the contact was poor (e.g. icy conditions), when both pantographs were raised. The motor cars were equipped with four traction motors, each driving one axle. After
World War 2 ten units were refurbished at
Waggonbau Görlitz and due to a shortage of
Jacobs bogies their trailer and control cars each received separate two axle bogies, increasing the total weight of the trainset. The modified units were designated as PKP class
EW52. In total 36 units were restored as either EW51 or EW52 and remained in service till the end of 1970's. A single unit has been preserved and transferred to the Warsaw Railway Museum but was allowed to gradually deteriorate at railway siding until 2018 when it was restored and preserved by ZNTK Mińsk Mazowiecki and in 2021 transported by the
Masovian Railways for static exhibition in the museums' main site by the
Warszawa Główna railway station. File:Otwarcie jednej z zelektryfikowanych linii warszawskiego węzła kolejowego.jpg|First electric train
Józefów railway station near
Otwock, December 15th, 1936 File: Bundesarchiv Bild 101I-695-0423-28, Warschauer Aufstand, Zivilisten auf Bahnhof.jpg|E91 electric multiple unit passing through
Warszawa Zachodnia station during the
Warsaw Uprising in August 1944 File:Lokomotywownia Warszawa Grochów, 1974.jpg|EW51 electric multiple units at a depot in
Grochów in 1974 File:Zdjęcie0103.jpg|A preserved 91000 abandoned at a railway siding at
Olszynka Grochowska, 2010 File:EW 51-36.jpg|EW51 after restoration in ZNTK Minsk Mazowiecki ==References==