Performance and Design of a Toroid-Coil Motor with Permanent Magnets

Electric motors with heteropolar surface magnets on the rotor and homopolar windings are suitable to get a simple and powerful small-sized stepping motor. Because of the search for a low-cost motor the concept of a toroid-coil motor with permanent magnets has been designed. Structure and specification are based on the threedimensional Finite Element Method (3D-FEM) presented in this paper. The 3D-FEM has been taken to calculate the magnetic field and the static torque has been computed with the Maxwell Stress Tensor Method. Analytical calculation has been used to investigate the influence of the pole pitch. The results are compared with test results of a prototype machine. Possible applications of the designed motor are stepper motors, servo applications, conveyor drives and direct drives.