A new design approach for reduction of force ripple in permanent magnet flux-switching linear motor

To reduce the force ripple of the permanent magnet flux-switching linear motor (PMFSLM), a new design approach is suggested by the authors. The detent force is redefined as the composite force of the thrust of the single action of permanent magnet and armature current. In the design approach, both the improved E-shaped PMFSLM primary module and secondary contain two units. The magnetisation direction of the permanent magnet in the two primary module units is opposite, but the two units share the same armature coil. The two units design eliminates the even number harmonics of the phase back-EMF and decreases the period of detent force. Through the design of the skewed secondary, the detent force is eliminated completely, and simultaneously, the odd-order harmonics are significantly weakened. The results of finite element analysis (FEA) show that the force ripple of the PMFSLM decreases significantly. Prototype experimental results are in good agreement with FEA results. The study results verify the effectiveness and practicability of the new design approach of PMFSLM for reducing the force ripple.