Design and Analysis of an Axial-Circumferential Modulation Linear Machine Based on 3-D Magnetic Field Coupling

Conventional linear machines operating in 2-D planar magnetic fields face electromagnetic loading limitations, struggling to achieve high thrust force density and strong overload capability. This article proposes an axial-circumferential modulation linear (ACML) machine to address this challenge. The key feature of the proposed ACML machine lies in designing a 3-D magnetic permeance that effectively couples the axial and circumferential magnetic fields. As the unique 3-D magnetic field coupling redefines traditional electromagnetic design constraints, the selection of pole-slot combinations becomes critical to leverage spatial harmonics for thrust enhancement. Consequently, the slot-pole combination of the ACML machine is discussed. Then, the operation principle is analyzed from the perspective of 3-D modulation theory. Furthermore, different structures of the linear machines are analyzed and compared, with the goal of optimizing thrust force and overload capability. Afterwards, an inner axial stator, outer circumferential rotor, and 3-D modulation translator are designed. Finally, an experimental platform is established to validate the role of the translator in the magnetic field modulation.