Analysis of the parasitic forces and torques in coreless linear motors

This paper concerns the analysis of parasitic forces and torques in coreless or air-cored linear synchronous motors with a U-shaped stator due to variation of the permanent magnet properties, manufacturing tolerances and power amplifier offsets. The parasitic forces and torques are analyzed using a 3D semi-analytical model based on surface charge modeling of the permanent magnets and numerical integration of the Lorentz force. Monte-Carlo simulations have been applied to carry out the tolerance analysis. Gaussian distributions of the tolerances are assumed. The paper shows that variation of the magnet properties, incorrect mounting of the translator and offsets in power amplifiers are the main cause of parasitic forces in this type of linear motors.