High-Speed Electric Drives: A Step Towards System Design

Electric drives applications have been worldwide adopted for the transportation electrification. An electric drive system is constituted by two main components: the power electronics converter and the electrical machine. Traditionally the design workflow consisted in the separate realization of these two parts, by different teams or even organizations. This requires strong assumptions regarding operating conditions and may lead to actual performance at system level far from the one expected. In this article, a unified design methodology of the two sub-systems is presented considering the true operating conditions, allowing a more accurate assessment of power losses at system level and identifying the influence of the converter design choices on the electric machine performance. As a case study, this article presents a comparative analysis among three different converter topologies designed to drive a 8.5 kW-120 krpm surface PMSM. The study aims at comparing the considered systems in terms of overall efficiency, losses distribution and system complexity. At first converters are simulated in Matlab-Simulink to estimate the losses and the current waveforms, that are then used in the Finite Element model of the electrical machine to estimate the loss components in a real scenario. The models developed are then validated by means of experimental measurements. This article highlights the new understanding that can be gained by considering the interactions between sub-systems, allowing a more conscious choice of the converter topology to achieve optimal overall performance.