Comparison of different winding schemes of an asynchronous machine driven by a multi-functional converter system

A comparison between different winding schemes has been carried out to optimize an asynchronous machine for an automotive electrical power steering system. The machine is driven from a multi-functional converter that consists of an inverter with integrated converter. This integrated converter provides an increased dc-link voltage to the inverter, but forces additional dc currents to flow through the machine windings. A detailed analysis is performed to describe the influence of the dc currents to the behavior of the machine and four most suitable winding schemes have been selected for the investigation. Results of the analysis demonstrate the requirement to carefully select the winding scheme when an asynchronous machine is operated from a multi-functional converter system. FEM simulations verify the results of the analysis. Four machines with different winding schemes have been built and tested together with the multi-functional converter. Experimental results are in close correlation with theoretical predictions.