Analyzing the influence of induction machine design on transient slot leakage inductance with respect to sensorless rotor position estimation

The paper analyzes the transient reaction of squirrel cage induction machines to voltage step excitation. The involved excitation technique uses the drive's inverter to excite the machine with voltage steps. The transient nature of these steps demands high flux linkage derivatives. In response, the squirrel cage acts as a barrier hindering the flux to penetrate the rotor yoke and forcing it into the air gap. Thus, the stator winding is linked to pure leakage flux, composed of slot and zig-zag leakage. A turning rotor modulates these flux components by changing the machine's magnetic permeances. Since these modulations are linked to the rotor slotting, they may be exploited to derive a rotor position signal. Understanding and predicting them is the key to assess different IM designs with respect to their applicability for sensorless position estimation. The investigation methodology used includes analytical modelling and finite element simulations, confirming the results of each other. Finally, different design variations are assessed.