Manufacturing Imperfections in Electric Motor Production with Focus on Halbach Array Permanent Magnet Rotor Assembly

In the production of electric motors, various manufacturing imperfections occur. These production-related deviations influence the product characteristics concerning power output, efficiency, vibration, noise and lifetime. However, measures to minimize manufacturing deviations are involved with several challenges such as additional measurements, advanced process control and above all costs. Thus, the benefit of possible improvement measures has to be carefully evaluated since not every production-related deviation has a significant impact on the product quality. Consequently, research is proceeding in this direction to quantify the actual influence of the various manufacturing imperfections on the motor characteristics as well as the whole drive system. To support the evaluation process, this paper gives a concise overview of the manufacturing imperfections in the production of permanent magnet synchronous motors (PMSM). A special focus is set on Halbach array rotors since these are particularly sensitive to magnetic deviations. As follows from first experiments, considerable deviations in magnitude and direction of the magnetization of the single magnets occur. The effects of these deviations are simulated on a specially developed Halbach test motor. Based on this, further effects will be investigated and practically tested using different motor configurations.