Analysis of Magnetic Gearing Effect in Field-Modulated Transverse Flux Linear Generator for Direct Drive Wave Energy Conversion

Direct drive wave energy conversion (DD-WEC) is a typical low-speed long-stroke application. Harvesting wave energy presents enormous challenges, because wave energy naturally exists in the form of extremely low speed, high force, or torque motion. However, the frequency of flux linkage in field-modulated machine can be increased by the magnetic gear effect, and the output voltage and power density can also be effectively enhanced. In this article, based on the field-modulated principle, a field-modulated transverse flux linear generator (FM-TFLG) is proposed. Different combinations of permanent magnet (PM) number, slot number, and translator number are selected and their performances are compared and analyzed. Results show that the electric frequency is enhanced as the modulation ratio increases. Compared with 18/12/17 (PM number/slot number/translator number) topology, 12/12/11 FM-TFLG has advantages of lower thrust ripple and total harmonic distortion (THD) of back electromotive force (EMF), higher thrust/power density, and efficiency. The proposed 12/12/11 FM-TFLG is a good candidate for DD-WEC.