Research on Inductance Unbalance and Thrust Ripple Suppression of Slot-Less Tubular Permanent Magnet Synchronous Linear Motor

Affected by the end effect, the inductances of the slot-less tubular permanent magnet synchronous linear motor (TPMSLM) are unbalanced. This paper reports the research on the inductance unbalance and the thrust ripple characteristics for the slot-less TPMSLM, and it presents an optimization scheme adopting modular structure with a three-segment primary component. The inductance unbalance characteristic is obtained and quantitatively investigated based on the finite element models. The causes of the self-inductance unbalance and the mutual-inductance are explained, respectively, and the difference between the two unbalances are quantitate investigated. Then, the thrust ripple is specifically analyzed by establishing the voltage and thrust models according to the laws of the inductance unbalance. Thus, the theoretical connection between the inductance unbalance and the thrust ripple has been established. Moreover, the inductance and thrust ripple characteristics of the modular motor are discussed and compared with those of the conventional motor. The prototypes of the conventional motor and the modular motor are developed to verify the findings of the research. At last, corresponding conclusions obtained by the comparison of modular motor with conventional motor are drawn.