Flux Density Waveform Reconstruction Method for Efficient Finite Element Analysis of Electric Motors

This paper proposes a procedure for optimizing the electromagnetic finite element analysis of synchronous electric motors. The methodology allows for the retrieval of the solution of the problem in an entire rotor rotation starting from simulations carried out within a reduced angle range, corresponding to the half of the electrical period divided by the number of phases of the motor winding. This is achieved by exploiting the geometrical periodicities of the motor and by dividing the static and rotating parts of the model in homologous sectors, which will undergo the exact same magnetic state, but with shifted waveforms with respect of the rotor angle. By properly rearranging the parts of the waveform taken from the different sectors, it is possible to reconstruct the full waveform in each part of the motor. A method to determine the waveform reconstruction sequence, i.e. the order in which the information should be taken from the different stator and rotor sectors, is defined as a function of the motor parameters. While a similar approach has been already presented in literature for specific motor designs and with the purpose of estimating iron losses, in this paper the methodology is generalized for motors with an arbitrary number of phases and is valid both for integer and fractional winding motors.