Three-dimensional eddy current computation in conductors of electric machines

In addition to terminal currents, windings in electric machines carry eddy currents that circulate only inside conductors. RMS values of eddy currents depend on magnitude and frequency of magnetic field in the conductor in which they flow and on conductor magnetic and electric properties. If conductor dimensions are significantly larger than the skin depth at supply frequency, the skin effect has to be considered when designing these machines. Thermal and electromagnetic relationships in an electric machine are three-dimensional and nonlinear-as a rule, they cannot be described with analytical expressions. Very often, the only way to find their three dimensional (3D) distribution is to apply finite element (FE) analysis. It is shown in this paper how a 3D FE computation not only makes possible the evaluation of eddy current distribution in electric machine conductors, but also how results of FE computations deepen the physical understanding of processes in these machines.