Analytical Model of the Ferromagnetic Properties in Laminations Damaged by Cutting

Electric motors with relatively small dimensions are widely used, among others, in household appliances. For this type of motors, the market imposes requirements for low electricity consumption and high operational reliability. Their final performance depend, inter alia, on the correct design of the magnetic cores taking into account the used production process and selecting the appropriate cutting technology. The presented paper deals with the problem to quantify the negative effects in terms of material characteristic degradation in magnetic laminations resulting from both punching and laser cutting. For this purpose, simple engineering measurements using a professional Single Sheet Tester system have been considered to develop accurate mathematical models. The proposed models are suitable for quick assessments of the material degradation for any width of the strip (or the motor core part) and, consequently, of the properties of the motors' cores. In the paper, the proposed analytical models are used to quantify the changes of the relative magnetic permeability vs. distance from the cut edge. The simulation results agree very well with the results of the measurements carried out according to the authors' concept.