Influences of material degradation due to laser cutting on the operating behaviour of PMSM using a continuous local material model

Abstract

During manufacturing of electrical machines, shape giving production steps such as punching and cutting introduce plastic deformations and residual stress to the soft magnetic material. As a result the magnetic properties of the material decreases and locally both, static and dynamic hysteresis losses increase in the vicinity of the cut surfaces. For consideration of local permeability deteriorations, different models have been published. These are capable to describe the changing local magnetisation and loss behaviour. Current approaches subdivide the magnetic core into slices of different magnetic properties, thereby discretising the continuous deterioration. This paper analyses the effects of material degradation due to cutting on the performance and machine parameters of a Permanent Magnet Synchronous Machine (PMSM) using a continuous material model for efficient numerical modelling of the local magnetisation behaviour. By replacing inefficient sliced models, the continuous model is independent of the discretisation and converges in case of coarse meshes to the sliced model. Influences on the machine behaviour are studied in terms of local flux density distributions, iron losses, efficiency, torque and inductances on the operating map and an exemplary working point.