New aspects for developing and optimizing modern motorcar generators

In modern motor vehicles there is a growing demand for electrical power due to the increasing number of loads while the available space for the generator is decreasing. In addition, the aspect of reducing fuel consumption is gaining more and more importance, Since the air-cooled claw pole generators which are used today do not allow a further significant increase in output power, new concepts of generators need to be developed. When doing so, some fundamental aspects must be researched to minimize the total losses. This results in new design objectives to increase efficiency and to reduce volume, weight and moment of inertia. As a novel solution of a high efficiency generator, a PM-excited synchronous machine with a disc rotor is presented. It is designed for an output power of 3 kW at a battery voltage of 24 V and a speed range of 3000 to 30000 r/min. Included is a chopper with a modern IGBT to match the battery voltage, which grants high constancy of the output voltage and excellent performance at sudden changes of load current