Development of analytical equations to calculate the cogging torque in transverse flux machines

Cogging torque is produced in a permanent magnet machine by magnetic attraction between the rotor permanent magnets and the stator teeth. It is an undesirable effect that contributes to torque ripple, vibration and noise of the machine. In this paper, the resultant cogging torque values are computed using a three-dimensional (3D) finite element analysis. For this, the rotor movement is modeled by means of the moving band technique in which a dynamic allocation of periodic or anti-periodic boundary conditions is performed. The 3D finite element method is the most accurate tool to carry out cogging torque. However, it does not easily allow a parametric study. For this reason, an analytical model was developed in order to predict the cogging torque. The tools are intended to be used for the study of transverse flux machines.