Flux and voltage calculations of induction motors supplied by low- and high-frequency currents

In order to precisely define the harmonic content of the main flux and stator voltage of an induction motor that is fed by a high-frequency carrier in addition to the normal set of stator voltages, this paper performs the analytical calculation of the zero-sequence components of the air-gap flux and stator voltage. The calculations are made by defining suitable winding functions to derive the self- and mutual inductances and by adopting a new inverse air-gap function to model the variation of the saturation level of the machine produced by the additional magnetomotive force. Analysis of the calculated expressions that are confirmed by experimental tests shows that the proposed analytical technique can be suitably applied to quantify the effects of high-frequency carriers on the air-gap flux and offers useful hints to understand sensorless control mechanisms. Index Terms--High-frequency modeling, induction machine, saturation, sensorless control.