Computational cost-effective modelling of non-linear characteristics in permanent magnet synchronous motors

Purpose - In the optimisation of electrical drives, the required degree of detail in the simulation increases constantly. Especially, the industrial demand on multi-objective optimisation craves for highly efficient models. The purpose of this paper is to propose a hybrid model for the computation of the air-gap field of a permanent magnet synchronous motor (PMSM) combining analytic and numeric methods. Design/methodology/approach - The classic conformal mapping (CM) approach is improved by the numeric approximation of the required ansatz-functions. This approach allows to consider the non-linear permeability of the applied materials and complex geometries. The non-linear permeance-function is described by a one-dimensional wave varying in time and space. Findings - The permeance-function has to be derived for different load cases at the actual stage. Research limitations/implications - A physical motivated modelling allowing for an appropriate interpolation between different load cases is planned in further research. Practical implications - The proposed approach is applied to a surface mounted PMSM. It is validated by means of a non-linear finite element analysis. Originality/value - The hybrid model offers to consider rotors with buried magnets using the CM approach. It is possible to either use analytic or numeric modelling of rotor ansatz-function, stator current ansatz-function and permeance-function with the proposed approach. Non-linear permeability of iron is modelled by means of a wave representation of the permeance-function. This can significantly reduce the computational cost in the design and optimisation stage of electrical machines.