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As compared to other renewable energy technologies, the ocean waves are huge, largely untapped energy resource, and the potential in extracting energy is considerable. There is a lack of convergence on the best method of extracting energy from the waves, despite previous innovations, which has generally focused on the concept and design of the wave energy converter (WEC) technology, making the strategies for enhancing the efficiency of WECs important. This paper presents the performance analysis and design optimization of a single-slotted permanent-magnet linear generator. The magnetic field distribution in a cylindrical coordinate has been established. The magnetic field provides a prediction for the thrust force, flux-linkage and back-electromotive force (B-EMF), and also facilitates the characterization of the proposed machine as well as provides a basis for design optimization and dynamic modeling of the system. Finite Element Analysis (FEA) has been used for the design optimization of the proposed generator. The proposed generator has been optimized with respect to the leading design parameters Rm/Re and Tmr/TP. Thus, from the results, it can be observed that the generator has a very good efficiency to serve as WEC. [ABSTRACT FROM AUTHOR]

Arrangement of permanent magnet (PM) poles and windings influences the magnetic field and force output of linear machines significantly. Various designs of PM linear machines have been proposed by researchers, either putting PM poles inside and coils outside, or vice versa. However, there is no systematic comparison of these two types of designs in literatures. The purpose of this study is to compare the magnetic field and force output of linear machines with different PM and winding structure topologies. Halbach array can not only produce high flux density, but also has self-shielding effect. So it is employed for the analysis. Tubular structure is used because it helps to reduce flux leakage and enhance the system output performance. The magnetic field distribution of tubular linear motors with internal and external PM poles are formulated with Bessel functions, and the force output is thus obtained from Lorenz force law. The analytical models of magnetic field and force output are then validated with numerical computations. By utilizing the verified analytical models, design optimization is conducted with penalty functions for the two machine structures. The magnetic field and force output performance are then compared. It shows that the machine structure with internal PM poles helps to generate high force output. The study in this paper can also be implemented for the design of rotary machines. [ABSTRACT FROM AUTHOR]

The E-core hybrid-excitation linear switched-flux permanent magnet machine (LSFPMM) is low cost, which not only accommodates armature and permanent magnets (PMs) in short primary, but also cuts half of PM volumes compared with its C-core counterpart. It also can easily adjust the air gap magnetic field flexibly through the injection of different DC currents. This paper introduces E-HELSFM with different end shapes firstly, while a shape with the best symmetry of flux and minimal detent force is developed and further investigated. Based on finite element model, the flux-adjusting principle of the proposed hybrid-excitation motor is presented, and certain geometric parameters are optimized for better flux-regulating capability and larger thrust force density. Then, the field ratio, which means the ratio of field area to a single slot area, is optimized to reach a tradeoff between force density and flux-adjusting capability. For the optimized model, the flux-adjusting as well as thrust force performances under different excitation conditions are investigated. Then, the flux-weakening control under different excitation levels is discussed. The simulated results show that the optimized machine exhibits good constant power operation capability through flux-weakening control and enhanced overload ability by flux-enhancing control. [ABSTRACT FROM AUTHOR]