High integration, low loss and high-reliability are the main development trends of flywheel energy storage [1]. Magnetic bearings (MB) [2] with several advantages, such as eliminating of a lubrication system, friction-free operation and low power consumption can be promoted in various practical industrial applications, especially in flywheel batteries. Brushless DC motor is widely used because of its high efficiency and simple control. The bearingless brushless DC motor (BBLDC) has the advantages of the above advantages, while it has the characteristics of small friction loss [3]. The problem of strong coupling between the magnetic field and the torque magnetic field can be solved by the double stator bearingless brushless DC motor (DS-BBLDC) [4]. Halbach permanent magnet structures are suitable for use in permanent magnet motors because they enhance the unidirectional magnetic field [5]-[6]. Thus, this study presents the first prototype of a Double Stator Halbach Permanent Magnet (DSHPM) BBLDC with the advantages of weak coupling and simple control. The structure, operation principle and main electromagnetic characteristics of the DSHPM BBLDC are analyzed. The proposed motor exhibits the following advantages: 1) High integration. The motor can not only realize the problem of energy conversion, but also realize two degrees of freedom (2-DOF) suspension control. 2) Low loss. The biased flux is provided by the permanent magnet which leaves out the extra biased winding correspondingly. 3) Weak coupling. The application of halbach structure can make motor rotor yoke adopt non-magnetic material to completely isolate torque system and suspension system. 4) Favorable controllability. The dual-stator structure of the torque system and suspension system separately control, to achieve a simplified control.
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