Structure Design And Optimization Of A Novel Linear Switched Flux Permanent Magnet Motor

Recently, linear switched-flux PM machine (LSFPMM) has become a research hotspot in the field of linear motor, especially for long stroke application. Compared with PM linear synchronous machine (PMLSM), LSFPMM has its PMs and armature windings on the short primary, and the long secondary is only made of slotted iron core, which not only greatly reduces the cost, but also maintains the advantages of PMLSM such as high thrust force density and high efficiency. However, with PMs inserted into primary teeth, the magnetic poles, windings and magnetic circuit are constrained by each other. Therefore, the thrust force density is limited and magnetic circuit is over saturated. What’s more, the heat generated by windings will influence the temperature of PMs, and cause them to demagnetize. To solve the above problems, a novel structure of LSFPMM with partitioned primary is proposed. This novel structure separates primary into two parts:one is the armature containing iron core and windings, the other is magnetic pole containing PMs and iron core. It’s also called asymmetric bilateral motor. Focusing on the design and optimization, a detailed and deep study is done.Firstly, the operation principle and mathematical model are introduced. Then, with maximum thrust force and minimum thrust force ripple as target, by using finite element method (FEM), optimal design is applied on a 9-slot/10-pole novel LSFPMM structure. The key parameters are optimized one by one. The end effect of linear motor is weakened by optimizing armature side teeth position and width. Then, electromagnetic performance of the optimal novel LSFPMM is analyzed. The comparisons of original and optimized structure are made. The difference between with or without end effect is analyzed, and it shows that end effect has significant influence on the machine performance, which should be carefully considered during design. Furthermore, the manufacturing errors are simulated and analyzed. Finally, the prototype is introduced, including the size adjustment for installation, and assembly situation.Through this study, some useful conclusions about novel LSFPMM are given, and it also sets a foundation for other similar partitioned primary motor structure.