128 001, as registered at Deutsche Bahn, or 12X, as named by its manufacturer AEG Schienenfahrzeuge and its successive owners ADtranz and Bombardier Transportation, is an experimental high-performance electric locomotive built in 1994, which was operated as testbed and test locomotive until 2010. The design of the locomotive featured several technological innovations, including power electronics using new types of semiconductors and water cooling, a new final drive concept, a new bogie concept, and protruding windflaps for improved aerodynamics that gave the locomotive a unique look.
The development of the locomotive was initiated in anticipation of a major tender for universal locomotives by German railways, but moved towards a modular design when the railways moved towards tendering different types of locomotives for different services. The 12X was the basis of a locomotive class for medium-weight freight trains, the DBAG Class 145, the further development of which ultimately led to Bombardier's TRAXX modular locomotive product platform.
History
DB Class 121 development
DB Class 120 was the first locomotive class of West German federal railway Deutsche Bundesbahn (DB) with three-phase asynchronous AC induction motors, and also the first implementation of the concept of the universal locomotive, which is suited for freight, passenger and express service alike. DB received the five prototypes from 1979, and all Germany-based locomotive manufacturers were involved in the delivery of the 60 series locomotives from 1987. In 1991, DB requested bids for an initial 500 universal locomotives with an improved design and a continuous power increased from , the planned DB Class 121. Former East German state railways Deutsche Reichsbahn also considered purchasing 200 units.
The competitors for the DB Class 121 order developed components and from December 1991, tested them in the prototypes of the DB Class 120, which were reclassified as the experimental Class 752. AEG Westinghouse, a supplier of electrical components for rail vehicles that was part of Daimler-Benz at the time, began developing a new final drive concept, a water-cooled converter based on GTO thyristors, an auxiliary converter, and a microprocessor-based traction control system. In 1992, AEG took over former East German locomotive manufacturer LEW Hennigsdorf and made it a subsidiary under its AEG Bahnsysteme (AEG Rail Systems) business area as AEG Schienenfahrzeuge GmbH (AEG Rail Vehicles Ltd). LEW was already developing lightweight vehicle body construction, better aerodynamics, and high-speed running gear. AEG bundled and continued these development efforts with the aim to produce a complete locomotive. The newly developed GTO thyristor based converter was built into DBAG 752 002 in late 1992 and started testing in January next year, the prototype of the new AEG final drive was built into series locomotive DB 120 118 and also began testing in 1993.
Project 12x
In the meantime, in October 1992, DB cancelled the Class 121 tender due to the high price of the offers, which made government approval for the investment unlikely, and the changed organisational and operational situation. The upcoming merger of Deutsche Bundesbahn and Deutsche Reichsbahn into Deutsche Bahn in 1994 coincided with a railway reform, dividing the rolling stock of Deutsche Bahn between its regional passenger, long-distance passenger and freight business areas, making the universal locomotive plans obsolete. The freight branch of DB was concerned in particular that express trains would be given priority in the use of shared universal locomotives. From late 1993, the business areas of Deutsche Bahn and their predecessors called new bids for electric locomotives tailored for their specific needs.