On the design of dual-stator windings for safe VSI fed AC machine drives

The major drawback of usual dual-stator AC machines supplied by a voltage source inverter (VSI) is the occurrence of large circulating harmonic currents, causing extra losses. This paper deals with the design of dual-stator winding AC machines for safe operation with VSI. A new reference frame model of a dual-stator induction machine (DSIM), including mutual leakage coupling, is proposed. The leakage inductance associated with the inaccurate harmonics is shown to have a quite small value, highly depending on the coil pitch. It is also shown that full pitch is required, and that special designs of slot shape should be investigated to limit the negative impact of circulating currents. Experimental results on a prototype of DSIM are presented and they show very good correlation with the theoretical curves.