Development of a Segmented Linear Variable Flux Reluctance Motor with DC-Field Coil

Abstract

This paper proposes a new type of linear motor based on the concept of variable flux reluctance motor (VFRM). By adopting segmented primary stator, the segmented linear VFRM (SLVFRM) can eliminate asymmetry between phases due to end-effect. Meanwhile, multi-phase SLVFRM of any number of phases can be obtained by adjusting number of segments directly. The stator/mover tooth pitch combination and segments arrangement rules are also illustrated. An optimized 3-phase SLVFRM is analyzed by finite element analysis, with focus on characteristics such as cogging force, back-EMF and winding inductances. Further, both brushless AC (BLAC) and brushless DC (BLDC) drive for SLVFRM are investigated. Besides much smaller force ripple, BLDC drive can obtain higher average force at same RMS current due to trapezoidal back-EMF. The force characteristicwith variousAC and DC currents and current angles are also investigated in the paper, and it shows that SLVFRM has negligible reluctance force while keeping the same AC and DC currents is optimal for maximum efficiency operation under a fixed copper loss.