Development of an Investigation Method to Analyse Effect of Laser Cutting on Iron Losses in an Electric Machine

Abstract: In this fast pace world, climate change is one of the primary concerns worldwide. The world is racing towards reducing CO2 emissions by focusing on decreasing energy consumption. Electric motors capture about two-third of the industrial energy consumption, of which the most growing sector is electrical vehicles. The precise design of electric motors requires an optimal estimation of the machine’s performance characteristics. In this master thesis, the impact on core losses of an electric machine (e-machine) due to laser cutting is studied. The impact is derived in terms of a mathematical model which is introduced in a finite element model of an e-machine to attain optimal performance characteristics. A customized Single Sheet Tester (SST) based measuring apparatus is developed. The measuring apparatus is used to characterize the magnetic materials (electrical steel) used in the core of an e-machine. The studies already presented in the literature compromise on maintaining the same material mass while characterizing the magnetic material. Thus, a novel approach is attempted in this work to maintain approximately the same mass for all test samples used for characterization. The samples under test are laser cut possessing different sample widths leading to different distances from the cut edge. The characterized samples are compared for magnetic properties such as permeability and core losses to derive a mathematical model to estimate the impact of degradation in electrical steel. The derived models are implemented in a reference Permanent Magnet Synchronous Machine (PMSM) to analyze the degradation effect on the loss and performance characteristics. The influence of laser cutting impacts drastically the iron losses at an average which increases by about 35 % with a corresponding reduction of 21 % in material permeability. There is an average increase in machine torque by about 2 % and the increase in the total iron losses leads to an average 0.5 % decrease in the efficiency of the machine. The increase in iron losses at lower magnetic flux densities is more significant compared to the saturation region. The maximum degradation effect in the material is nearer to the cutting edge and reduces going away from the cut-edge. The permeability in the material decreases closer to the cut edge and thus the maximum amount of flux gets enforced towards the center because of degradation.