Magnetic Equivalent Circuit Modeling of a Saturated Surface-Mounted Permanent Magnet Synchronous Machine

Permanent magnet synchronous machines are often designed to generate a maximum torque through thermal-limited short-time operation in the overload range. Therein, almost all machines suffer from significant magnetic saturation. Classical models used in the controller design are not suitable to systematically account for magnetic saturation or inhomogeneous air gap geometries. This paper introduces a magnetic equivalent circuit model of a surface-mounted permanent magnet synchronous machine that inherently describes the saturation phenomenon. The comprehensive permeance network is solved based on graph theory. Furthermore, the systematic incorporation of the flux dynamics and the electric interconnection of the coils results in a dynamic model represented by a set of nonlinear differential-algebraic equations that has a minimum number of states and a unique solution. Finally, the proposed machine model is calibrated and validated by means of measurement results.