Tramway Cottbus

Delivery: 2005

IGBT-Chopper Traction Equipment for Articulated Tramcars KT-NF6 of the Cottbusverkehr GmbH.

The tramway lines in the German city of Cottbus are approximately 30 kilometres long. In 1996 the rolling stock consisted mainly of 64 short articulated tramcars, type KT4D, supplied by CKD Tatra/Praha. For cost reasons a considerable number of Tatra vehicles will have to guarantee the passenger service in the future, even though public transport is being extended with new aspects.

26 of these motor cars have been modernised by insertion of a low-floor center part easier to access by handicapped people. The intentions to be achieved for these vehicles were:

• increasing of availability

• reduction of maintenance

• saving of energy

• more reliability and more travel comfort

to meet the requirements of a modern public transport service.

In order to obtain these objectives Kiepe elaborated a propulsion package which as main item includes a modern, compact chopper in IGBT-technology replacing the accelerator and keeping the existing traction motors. A clear reduction of weight and volume as compared to conventional GTO-technology argues particularly in favour of this device. Its design allows the installation in cars which are to be modernised or in mechanically already modernised vehicles at low expenditure. The reconditioning to KTNF6 by inserting a low-floor central part and the other modernizations are carried out by the Mittenwalder Gerätebau GmbH. The advantages of the relatively new IGBT-technology (IGBT = Insulated Gate Bipolar Transistor), especially as compared to the well-established GTO-technology (GTO = Gate Turn Off-thyristor) are the simple design of the IGBT-Chopper, a nearly non-volatile triggering of the IGBT as well as the higher clock frequency. Due to the higher clock frequency the auxiliary motor choke becomes unnecessary leading to reductions of weight, volume and cost. Thus, the IGBT-Chopper presents a very modern and trendsetting propulsion system and an economical modernisation measure for existing vehicles with conventional DC power control. The IGBT-Chopper is controlled by an electronic microprocessor drive/brake control unit.

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