Abstract
This paper presents an analytical method for modeling the no-load air gap flux density of a surface-mounted and a consequent-pole linear Vernier hybrid machine (LVHM). The approach is based on simple magneto-motive force (MMF) and permeance functions to account for the doubly-slotted air gap of the LVHM. These models are used to determine the flux linkage, induced electromotive force (EMF) and average thrust force of each machine. The accuracy of the two analytical models is validated by comparison with 2D finite element method (FEM) solutions. Based on the analytical models, it is found that the working harmonics of both surface-mounted and consequent-pole LVHMs are essentially the same. However, the magnitudes of these working harmonics in the consequent-pole LVHM are invariably greater than those of surface-mounted LVHM. Further, using the analytical model, the contribution to the thrust force of the machine by each individual working harmonic can be shown clearly, and is used to explain why the consequent-pole LVHM has improved performance despite using only 50% of the permanent magnet (PM) material compared to the surface-mounted LVHM.
Highlights
The use of linear electrical machines in direct-drive applications has become increasingly attractive, as they eliminate the need for intermediate linear-to-rotary conversion systems
In this paper, the analytical models for the no-load air gap flux density of the SM and consequent pole (CP) linear Vernier hybrid machine (LVHM) were derived based on magneto-motive force (MMF)-permeance theory
Detailed comparisons with 2D finite element method (FEM) show that the developed analytical models accurately predict the no-load air gap field distributions of both machines
Summary
The use of linear electrical machines in direct-drive applications has become increasingly attractive, as they eliminate the need for intermediate linear-to-rotary conversion systems. There are a number of electrical machine technologies, the variable reluctance permanent magnet (PM) machine technologies are well-suited for these low-velocity and high-force direct-drive applications These machines operate according to the flux modulation principle, where the PM field magneto-motive force (MMF) is modulated by a varying air gap permeance. Similar to [4], a magnetic equivalent circuit (MEC) representing the PM-to-consequent-pole flux pattern is used to explain the reduction in flux leakage and associated performance improvement in [1] These over-simplified models are unsuitable for more in-depth analysis of the air gap field distribution and force-producing mechanisms of LVHMs. In this paper, the analytical models of the air gap flux density for both SM and CP LVHMs are developed based on MMF-permeance theory.
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