Tangential and Normal Force Generation-Mechanism in Permanent Magnet Linear Synchronous Motors

This paper presents the studies on the force generation-mechanism of iron-cored permanent-magnet linear synchronous motors (PMLSMs) by introducing the field-decomposition method in the D-Q axes. Using the proposed field-decomposition method (FDM), the force generation-mechanism can be analytically described for i) the geometry-driven and current-driven motor forces, ii) the generated DC motor forces in normal and tangential directions, iii) the harmonics of AC force ripples caused by end- and slotting-effect, together with the perpendicularly-coupled forces by D-Q currents, and iv) the force equations for all the decomposed motor forces. This paper also presents the experimental validation of the FDM and the associated PMLSM force generation-mechanism by directly measuring various types of forces. The significant agreement is confirmed between the experimental results and the prediction by the proposed method on the current and force relationship, the DC and AC force generation, and the force ripple harmonics.