An approach for performance prediction of saturated brushed permanent magnet direct current (DC) motor from physical dimensions

An analytical approach for performance prediction of saturated brushed permanent magnet direct current (DC) motors is proposed in this paper. In case of a heavy saturation in the stator back core of electrical machines, some flux completes its path through the surrounding air, and the conventional equivalent circuit cannot be used anymore. This issue has not been addressed in the literature. The importance of considering the effect of the flux penetrating the surrounding air is shown in this paper using finite element simulations and experimental results, and an analytical approach is proposed to consider this effect on magnet operating point determination and performance prediction of saturated brushed permanent magnet DC motors. An analytical method is also presented to determine the boundary radius of the surrounding air for obtaining accurate results in finite element (FE) solutions and analytical calculations. An analytical approach based on Carter’s coefficient is also proposed to calculate the effective length of the magnet when the length of the magnet and rotor length are not the same. The accuracy of the proposed analytical model is illustrated using finite element simulations and experimental results. With this accuracy, this analytical model is very suitable to be used for reliable and quick mathematical design optimization.