Numerical modelling of the rotor movement in a permanent-magnet stepper motor

This study deals with predicting the dynamic behaviour of the rotor in a claw-poled, permanent-magnet (PM) stepper motor. The finite element method (FEM) model of a prototype stepper is used to calculate the magnetic forces on the rotor, where the PM is modelled with an altered geometry approach. This altered geometry helps achieving a realistic magnetic flux density profile and direct PM material property input. The obtained forces are used in the following analysis as the excitation, to simulate the rotor´s rotational and also axial movements with the help of proposed system of equations. To validate the introduced modelling approach, a measurement of the rotational and axial movement was performed on a motor with the same geometry and material properties. The results of the simulated movement are in good agreement with the experimental data for the tested motor.