Research on a Tubular Primary Permanent-Magnet Linear Generator for Wave Energy Conversions

A tubular primary-permanent magnet linear generator (TPPMLG), where both the magnets and armature windings are placed in the primary, is proposed for the sea-wave energy conversion. There is a simple structure on the secondary of the generator. Based on the model of proposed TPPMLG, the operation principle is analyzed. To investigate the electromagnetic characteristics and the unique advantages of the proposed generator, an optimized tubular secondary permanent-magnet linear generator (TSPMLG) is compared with the TPPMLG. Axisymmetrical dimensional finite-element method (FEM) is implemented to calculate the magnetic fields of the two generators and obtain the nonload and load performance. The results of finite-element analysis (FEA) indicate that the proposed generator has the advantages of sinusoidal voltage, minor detent force, high generating efficiency, and good performance at lower speed. Two prototypes are used to validate the results of FEA.