An improved structure for axial-flux eddy current couplings with combined rectangleshaped magnets is proposed to minimize cogging torque without sacrificing torque density. Then, a novel analytical electromagnetic-thermal model, which takes the change of material electromagnetic and thermal characteristics under temperature, is presented to calculate cogging torque, electromagnetic torque, and eddy current loss and temperature. The model is valid for the whole working area. The magnetic field distribution is calculated by the quasi 3-D electromagnetic field analytical model. Then cogging torque, electromagnetic torque, and eddy current loss can be obtained. Furthermore, an equivalent thermal resistance network model is established. The thermal model takes the previously obtained eddy current losses as the heat source, which is the eddy current loss of copper and copper back iron. With the help of the electromagnetic-thermal model, the characteristics of slip on electromagnetic torque, eddy current loss, and copper and permanent magnet temperature rise is also analyzed under the whole working range. The validity of the electromagnetic-thermal model is confirmed with finite element method and measurement.
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