Evaluation of an Induction Machine's Differential High Frequency Inductance for Self-Sensing Control Considering Iron Saturation

The saturation-dependent anisotropy of an induction machine (IM) is not rotor fixed and therefore constitutes a disturbance factor, which limits the controllability at low speed if the machine is to be operated with a self-sensing control. This paper describes a method to evaluate the differential high frequency (HF) inductance, which considers the saturation-dependent anisotropy by using transient finite element analysis (FEA) simulations with and without an injected carrier signal (CS). The voltage and current responses to the CS are extracted by eliminating the intersections of the two simulations. This allows analyzing the differential HF inductance without any overlay of interfering influences. Furthermore, the HF field distribution is visualized, giving insights into the physical origin of the saturation-dependent anisotropy and enabling the investigation of measures to reduce it.