Analytical methods for the accurate computation of stator leakage inductances in multi-phase synchronous machines

Multi-phase machines are of increasing importance in today´s electric drives and generation systems. While in three-phase machines stator leakage flux phenomena are usually described with a single parameter, a higher number of independent leakage inductances is required as the number of phases increases. The impact of leakage inductances on multi-phase machine performance, especially in PWM inverter-supplied motors, is proved by many studies. Hence the need originates for the electromagnetic designer to have easy-to-use but sufficiently accurate calculation formulas giving the complete set of mutual inductance in a multi-phase machine. This paper aims at providing such formulas making abstraction of the particular phase arrangement in the stator winding and under the hypothesis of equal phase belts. The computation algorithms provided are assessed against measurements on actual machines wherever possible; otherwise accurate Finite Element (FE) analyses are used for validation.