Simulating the change of magnetic properties of electrical steel sheets due to punching

Electrical machines are, especially in combination with modern power electronics, the driving horse in industry, traction and automotive applications. So there is a lot of research ongoing in the fields of new or improved topologies, better performance and increased efficiency. Latter one requires a better knowledge of the loss mechanisms in the machine in order to find solutions to reduce them. The iron losses, resulting from a varying magnetization in the ferromagnetic lamination sheets, are the most complex loss component in an electrical machine. One factor influencing the iron losses significantly is the manufacturing process. Among the different production steps, punching of the machines lamination can be considered to have a very high impact on the magnetic properties. If there is knowledge on how these properties depend on the mechanical and the process parameters there is considerable potential to optimize the process or the machine design to increase the machines efficiency. This paper will present simulation models trying to forecast the losses of punched lamination sheets. Therefore, the punching process was simulated with Finite-Element software. The resulting distribution of mechanical stress and plastic strain was incorporated in the Jiles-Atherton model to calculate the magnetic hysteresis of the lamination sheet. A comparison with measurements will show the applicability of the methodology.