Low floor trams with IGBT-3-level inverter

The development of the IGBT module has made it conceivable to realise single axle drives for low floor trams. A modular construction with low maintenance requirements is achieved through isolated mounting and forced air cooling. Special measures have to be taken to protect motors and their environment due to the extreme rise of voltage during switching of the IGBTs. Every single axle drive functions with its own control-unit. This type of system enables the separation of actual motor control from the function of protection. Such a system then eases demands on the overall control device improving functionality and reliability. The control device is built up by the use of 80C166 microcontrollers, the logical functions of the protection unit are realised with logic cell arrays (LCAs). Actual values of the field oriented control are estimated with a digital flux observer. To compensate calculation times of the microprocessor system, a prediciton of the estimated values is implemented