Impact of electrical steel punching process on performance of switched reluctance motors

Electric motors consume around half the global electric power generation and increased concern with reducing electric energy consumption has made the development of high efficiency motors more important. As the core material in electric motors, electrical steels may suffer from degradation of magnetic properties caused by manufacturing processes. For example, the punching may cause dislocations, residual stress, cracking or deformation to the grains at the lamination cut edges [1]. This would then result in lower motor efficiency than expected. Previous research [2,3] has investigated the effects of fabrication on electric motors but focused on iron losses. More effort is much needed to fully understand this impact. It would be beneficial if the motor performance considering manufacturing impact can be accurately predicted in design stage. However, this remains a challenge since there are still many uncertain factors. For instance, it is difficult to estimate the depth of the damaged zone due to punching [4], and one of the factors that greatly affect this depth is molding quality. The magnetic property, such as iron loss of the material in the damaged zone is also hard to predict.