Linear primary permanent magnet vernier machine for wave energy conversion

In this paper, a new linear primary permanent magnet vernier (LPPMV) machine is developed for direct-drive wave energy conversion. Owing to the magnetic gearing effect, the LPPMV machine possesses the advantages of high thrust force and low speed motion. After describing the machine structure, the operation principle of the machine is analysed and compared using two methods, namely, the magnetic gearing principle and the straightforward magnetic path. Then the characteristics are analysed by using the finite element method. Considering the unbalance of the no-load flux linkage and the inductance among the three phases, the mathematical model of the proposed machine is established, which is significantly different to that of the traditional permanent magnet machine. Finally, the machine is prototyped and tested so as to experimentally verify the theoretical analysis.