Thrust Generation Mechanism of a Hybrid Excitation Field Modulated Transverse Flux Linear Generator by Magnetic Field Modulation Theory

The magnetic field modulated transverse flux linear machine (TFLM) effectively combines the advantages of magnetic field modulated machine and TFLM, exhibiting high power density at low speed, effectively blocking eddy currents, and improving machine efficiency. However, its thrust generation mechanism is hard to analyze due to its complex three-dimensional (3-D) magnetic circuit structure. In this article, the thrust generation mechanism of hybrid excitation field modulated transverse flux linear generator (HE-FM-TFLG) is analyzed from the perspective of 3-D magnetic field modulation. First, the machine configuration of HE-FM-TFLG is introduced. Then, considering 3-D magnetic field modulation and hybrid excitation structure, the main harmonic and thrust characteristics of HE-FM-TFLG are derived based on magnetomotive force (MMF)-permeance model. A HE-FM-TFLG prototype is manufactured, and a prototype experiment platform is built to test the electromagnetic characteristics of the prototype. Both finite element method (FEM) and experimental results demonstrate that increasing the excitation current not only enhances thrust but also reduces no-load back electromotive force (EMF) total harmonic distortion (THD), thereby improving power quality. The prototype employs cross-connected windings simultaneously in both the circumferential and axial directions to reduce thrust ripple. Moreover, the hybrid excitation structure endows it with flux regulation capability. This enables it to better capture wave energy for power generation when there is a certain degree of variation in wave speed. The effectiveness of the analytical results is verified by FEM results and experimental results.