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Considering the fluctuating price of permanent magnet, magnetless machine is a new trend in development. Variable reluctance linear machines (VRLM) with simple structure, good robustness, and high dynamic performance, is one of the potential candidates for linear direct-drive wave energy conversion (WEC) application replacing PM-excited linear machine. To ameliorate the fault-tolerance performance of VRLM, the researchers have come up with modular or segmented design, denoted as modular variable reluctance linear machines (MVRLM) However, suffering from large thrust ripple, the design of MVRLM still needs to be improved. To relieve the force ripple of MVRLM, a novel H-shaped modular variable-flux linear reluctance machine (HMVF-LRM) is proposed in this paper. The principle of force ripple suppression by using parallel-complementary structure is analyzed deeply. In this paper, the analytical calculation of induced voltage is developed quantitively with equivalent magnetic circuit method (EMC) and harmonics analysis. Then the design mechanism of HMVF-LRM is illustrated. Further, the performance and fault-tolerant capability of the proposed machine are simulated and evaluated by finite element analysis (FEA), and the prototype is tested to verify the effectiveness of the machine design.

Finite element method (FEM) has become a very popular and practical tool for computing the magnetic fields in electrical machinery. Such numerical techniques enable the designer to study the problems that are difficult to be solved by analytical methods. This paper attempts to summarise the application of FEM in analysing the performance of induction motors. Different FEM involving a 2D magnetostatic model, a 2D complex eddy current model, a 2D rotating model, a 2D FEM coupled with circuit equations model and a 3D model are discussed. The merits and limitations of the various models are outlined. Further developments are also discussed by the authors.