Converter Propulsion Systems with Three-Phase Induction Motors for Electric Traction Vehicles

Three-phase induction machines have a number of advantages compared with collector type machines which make them particularly suitable for traction purposes. These advantages, which were recognized long before, could only be used in praxis by means of the progress, which the development of static power converters has made in the last decade. Primarily having been used in diesel-electric traction vehicles inverter-fed three-phase induction motors are now going to be applied in large scale to line-fed electric vehicles. In this field of application the induction machine has some additional advantages; e.g., the motor torque versus speed curve declines much less with increasing speed than that of the common series wound ac machine. Consequently, for the first time in history universal electric locomotives can be built, which are equally suited for hauling high-speed passenger trains as well as heavy freight trains. Converter systems are described, which do not drain reactive power from the supply line or even feed reactive power into the line, if necessary, and produce only a small amount of harmonics. Hence these systems are very well suited for high-power electric traction vehicles as well as for smaller vehicles, which are in service simultaneously in one district (e.g., rapid transit vehicles), and for industrial locomotives. Finally, some test and production vehicles with three-phase induction motors, test data, and experiences in service of such vehicles are described.