Improved Core Loss Calculations in Soft Magnetic Composites Considering 3-D Magnetic Flux Density Vectors and Geometry Dependent Eddy Currents

This paper explains the mechanism of core loss calculations in three-dimensional (3-D) flux electrical machines with soft magnetic composite materials. The nature of magnetic fields in SMC is 3-D and rotational. In traditional laminated electrical machines, the magnetic field is assumed to be alternating and along an axis. Soft magnetic composites differ from laminated steels in terms of magnetic field distribution within material. Electrical resistivity measurements in different grades of SMC indicate that these magnetic materials usually do not have a unique value of electrical resistivity at a given temperature. This causes discrepancy in loss computations through finite element electromagnetic simulations. Electrical resistivity of SMC components might be avoided in computation of power losses. Therefore, we propose empirically modified Steinmetz equation coefficients for different grades of SMC materials which can be used by other machine designers. The data was obtained by experiments and has been further implemented in more general forms of Steinmetz’s law. The three-dimensional magnetic field vectors in SMC based electrical machines have been incorporated into some useful mathematical equations to compute the losses accurately.