Design of slotted permanent magnet linear synchronous motor for improved thrust density

Since a linear motor with high thrust density and low thrust ripple is desired for many industrial applications, in this paper, a design methodology is proposed to achieve these objectives. A slotted permanent magnet linear synchronous motor (SPMLSM) which inherently offers the highest force density among various types of linear motors is selected for analysis and optimization procedure. An analytical model is derived for the SPMLSM by solving Maxwell´s equations for calculating the magnetic field and force. Motor dimensions are then optimized using the analytical model and genetic algorithm, where the increase of force density and the reduction of thrust ripple are considered as the optimization target. In this study, to reach a higher optimal point in the multidimensional search space of the machine design, cogging force caused by slot effect is initially neglected in the model. Subsequently, pole-shifting is applied to the optimal model to eliminate cogging force and satisfy design objectives. Finally, the effectiveness of the proposed technique to enhance motor performance is investigated by a time-stepping transient finite-element method. The results show an improvement in the performance of optimized motor.