A linear to rotary magnetic gear

Abstract

Although magnetic gears are more expensive and larger than mechanical gears for a given power rating, they are more efficient. They also offer the advantage of physical separation between the driving and driven shafts which can be in different environments, e.g., in water and in air. Recent research has focused on rotary magnetic gears, with limited work on linear to rotary and vice versa motion conversions, which is desirable in many applications such as wave energy harvesting. This thesis focuses on the development of the theory and design optimisation of a novel
linear-rotary magnetic gear derived from a variable reluctance permanent magnet (transverse-flux) rotational machine topology. The configuration of a linear to rotary magnetic gear is developed and discussed. A design optimisation methodology is implemented based on finite element analysis. Using this methodology, optimal proportions
and dimensions of a linear to rotary magnetic gear demonstrator are determined. It is shown that increasing the magnet thickness results in the increase transmitted torque, but with diminishing returns. The optimal results showed that the maximum torque density obtained
about 11.3 kNm/m³. The proposed design methodology is successfully applied to the design of a two-pole (on the rotor) magnetic gear. A demonstrator is built and successfully tested, and theoretical predictions are validated. Based on the demonstrator in this study, the use of a linear-rotary magnetic gear for applications such as wave energy harvesting looks promising.

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