Influence of Longitudinal End-Effects on Electromagnetic Performance of a Permanent Magnet Slotless Linear Launcher

Longitudinal end-effects seriously affect the electromagnetic performance of linear motor especially for large volume devices such as electromagnetic launchers. So, the purpose of this paper is to study longitudinal end-effects in a permanent magnet (PM) slotless linear launcher and proposes some measures for improvement. The longitudinal end-effects induced by finite length of PM mover can give rise to two mechanisms, uneven airgap magnetic field and partial saturation. The splitting edge magnets method is used to improve the uniformity of flux distribution, and it is also beneficial for enhancing thrust. In addition, we focus on asymmetrical phase characteristics stemming from finite stator part with distributed windings. Its influence on thrust and thrust ripple are investigated based on symmetrical component and energy method. The comprehensive analyses are established to aid initial design and assessment of performance for PM slotless linear launcher.