Detent Force Minimization of Double-Sided Permanent Magnet Linear Synchronous Machine with 120° Phase Belt Toroidal Windings by Slot-Shift Structure

Jikai Si,Yihua Hu,Yingsheng Li,Xiaobao Chai,Rui Nie

doi:10.3390/en15030943

Abstract

Double-sided permanent magnet linear synchronous machine with 120° phase belt toroidal windings (120°-TWDSPMLSM) suffers from large detent force due to the end effect and slot effect. Many existing methods can reduce the detent force of the 120°-TWDSPMLSM effectively. But they also minimize the back electromotive force (back-EMF) and thrust simultaneously. To alleviate this problem, this paper adopts a method of combining slot-shift structure with rearranging the 120° phase belt toroidal windings (120°-TW) to suppress the detent force and improve the back-EMF and thrust of the 120°-TWDSPMLSM simultaneously. First, the slots on the two sides of the primary part are stagger by an optimal distance to reduce the detent force. The models of the detent force, including the end force and cogging force, is established theoretically, and then verified by finite-element analysis (FA). Then, the 120°-TW are rearranged to improve the back-EMF and average thrust. And the electromagnetic characteristics of the 120°-TWDSPMLSM under different shifted distances are analyzed and compared in detail. Finally, the result shows that the detent force of optimized machine is 70.19% lower than that of the original machine, and the thrust fluctuation reduces 19.21%. Besides, the back-EMF of optimized machine is 6.84% lower than that of the original machine, but 31.86 higher than the machine with shifting slots and without rearranging the 120°-TW. Therefore, the optimal method in this paper is available in the detent force reduction and thrust improvement of the 120°-DSPMLSM.

Highlights

The double-sided permanent magnet linear synchronous machine (DSPMLSM) is widely used in various industrial applications and daily life, such as material and express handling and transportation, owing to the simple structure, high thrust density, low maintenance cost, and unilateral magnetic force [1,2,3,4]. It suffers from large detent force which includes the end force owing to the longitudinal end effect and cogging force due to slot effect of the DSPMLSM
It is of great significance to suppress the detent force of the DSPMLSM
This paper adopts a method of combining slot-shift primary structure with rearranging the 120◦ phase belt toroidal windings (120◦-TW) to suppress the detent force and improve the back-EMF and thrust of the DSPMLSM with 120◦-TW (120◦-TWDSPMLSM) simultaneously

Summary

Introduction

The double-sided permanent magnet linear synchronous machine (DSPMLSM) is widely used in various industrial applications and daily life, such as material and express handling and transportation, owing to the simple structure, high thrust density, low maintenance cost, and unilateral magnetic force [1,2,3,4]. In order to solve the problem, Huang et al proposed shifting one of the primary components by a certain distance, which could decrease detent force effectively in a DSPMLSM [18] and improve the thrust by changing the winding arrangements of the distributed and short-pitch windings. This paper adopts a method of combining slot-shift primary structure with rearranging the 120◦-TW to suppress the detent force and improve the back-EMF and thrust of the DSPMLSM with 120◦-TW (120◦-TWDSPMLSM) simultaneously. Since the lengths and structure of the upper and lower primaries are same, the amplitude of the Fn1 and Fn2 are identical, namely Fn1 = Fn2 = Fn. the end force of the whole DSPMLSM fend is shown in Formulas (4) and (5) [21]. When S is equal to 1, the fundamental amplitude of the end force of the entire primary is twice of the single upper (or lower) primary

Simulation and Verification of End Force

Thrust Characteristic

Findings

Conclusions