Reversal‐Halbach PM Array Design to Suppress Thrust Ripple of a Linear Primary PM Vernier Machine

ABSTRACT

The linear primary permanent‐magnet vernier machine (LPPMVM) is a promising candidate for long‐stroke applications owing to its high thrust density and cost‐effectiveness. Nevertheless, significant thrust ripple persists due to rich spatial harmonics in the air‐gap magnetic field. To address this limitation, this paper proposes a novel linear primary permanent magnet vernier machine incorporating a reverse Halbach array (RH‐LPPMVM). The core innovation lies in the synergistic use of reversed magnetisation segments and a deliberate permeance phase shift to selectively attenuate specific harmonic orders in the armature flux density distribution. Analytical and finite‐element studies reveal that the 2nd and 22nd harmonic components dominate electromagnetic force fluctuations. By suppressing these critical harmonics through the proposed reverse‐Halbach design, the RH‐LPPMVM achieves a significant reduction in thrust ripple while maintaining the average thrust. Experimental validation on a prototype confirms the overall effectiveness of the proposed method, though discrepancies between predicted and measured ripple are discussed and attributed to practical manufacturing factors.