Design and loss assessment of air cored axial flux permanent magnet machines

This paper focuses on different calculation methods of Joule losses in a winding and Halbach magnet arrays for air cored axial flux motors. The classical approach (I) for winding losses results in eddy current losses without proximity effect but with induced currents for the passing magnetic field. The second method (II) derives the frequency dependent resistance including skin and proximity effects to calculate the winding losses due to higher current harmonics generated by pulse width modulation (PWM) excitation. The calculation of eddy currents (III) induced by higher harmonics in the magnet array is used to evaluate two different assembly strategies concerning the joule losses within the magnets. Based on the results from these three methods, final design decisions were made. A full-scale prototype in-wheel hub motor was manufactured and measured to assess the chosen design.