Techniques for reducing the effects of detent force in PMLSMs [permanent magnet linear synchronous motors]

The detent force of permanent magnet linear synchronous motors (PMLSMs) generally causes undesired vibration and noise. Two different reduction techniques are proposed to reduce the detent force. The technique, by optimizing the structure of the primary core, can reduce the detent force effectively but can not remove the detent force. This method is based on the finite element method (FEM) and Fourier analysis, and the effect of adjusting the length of the primary core and adopting a fractional slot structure are investigated. Another technique is by improving the control algorithm with a force compensator to counteract the detent force effects. The speed response experimental results show that the peak to peak speed ripple is about only 2% by employing the proposed techniques.