Comparison between Halbach Array Rotors with Discrete and Continuous Magnets for Aeronautic Applications

The torque and power density are some of the key design drivers for electrical machines used in aeronautic and aerospace applications. In this paper, a comparison between two electrical machines comprising a conventional Halbach array rotor and a novel Shaped-Field Magnet (SFM) rotor, respectively, is completed. SFMs exhibit a spatially rotating pattern of magnetization in one single magnet, unlike a conventional discrete Halbach array, which comprises several magnets with a uniform magnetization direction. The objective is to evaluate the advantages and the drawbacks of continuous SFM rotors, and to estimate the potential benefits of this technology. The comparison is based on a Finite Element Analysis (FEA) applied to an existing electrical machine designed for an aeronautic application, and comprising a conventional Halbach array rotor. Results show that the use of SFM allows for a 10% increase in electrical machine power density. This increase is obtained with no other modification of the machine than the Permanent Magnets (PM) structure.