Nonlinear modeling of a permanent-magnet induction machine

This paper presents the nonlinear modeling of a permanent-magnet induction machine (PMIM). The PMIM has a permanent-magnet (PM) rotor that is free to rotate inside a squirrel-cage rotor. The internal self-excitation from this PM rotor allows the PMIM to operate at a higher power factor. Utilizing a duality between magnetic and electric circuits, an electrical equivalent circuit that can accurately include the nonlinearity of the excitation circuit is derived. Based on this equivalent circuit, a measuring method of circuit parameters and a calculation method of the steady-state performance are explained. In addition, the generating characteristics of the PMIM in the grid-connected mode are theoretically calculated to verify the validity of the derived equivalent circuit, and the results are confirmed through experiments. © 2003 Wiley Periodicals, Inc.