Load dump transient control of a 42 V automotive generator

This paper describes the concept, design, modeling, simulation and performance of an innovative fast field regulator developed for a high-power 42 V automotive generator, to minimize the load-dump energy and improve its reliability. In laboratory tests, a 3 kW 42 V Lundell generator, with conventional field regulator, failed the load-dump transient test. This research analyzed the root cause of the failure by analyzing the load-dump energy, using SABER modeling and simulation, which have been verified by tests. Various concept alternatives for minimizing the load-dump energy have been identified and an innovative and cost-effective solution based on fast field control was selected for development of the proof-of-concept hardware. The proposed technique reduced the load-dump transient duration by more than a factor of 5, resulting in a reduction of load-dump energy by more than 75%. This eliminated the need for paralleling multiple avalanche diodes in the alternator rectifier bridge to handle the transient energy, resulting in a smaller package and increased reliability at a lower cost. The proposed fast field control can be further applied to minimize the load-dump transients in all belted alternator starters (BAS) that use a wound-field machine.