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1. A High Torque Density Halbach Rotor Coaxial Magnetic Gear

   Hong, H Y; Bird, J Z; Barnett, D; Williams, W. (January 2019, IEEE International Conference on Electrical Machines and Drives)

   This paper presents the design, analysis, and experimental testing results for a 5.67:1 Halbach rotor magnetic gearbox with a ferromagnetic back support. Using 3-D finite element analysis software the Halbach magnetic gearbox was calculated to achieve a volumetric torque density of 284N·m/L with only an active region outer diameter of 120mm. The experimental prototype obtained an active region volumetric torque density of 261.4N·m/L 

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2. High Fidelity Dynamic Modeling and Control of Power Regenerative Hydrostatic Wind Turbine Test Platform

   https://doi.org/10.1115/FPMC2018-8900  

   Mohanty, Biswaranjan; Stelson, Kim A. (September 2018, High Fidelity Dynamic Modeling and Control of Power Regenerative Hydrostatic Wind Turbine Test Platform)

   Conventional wind turbines are equipped with multi-stage fixed-ratio gearboxes to transmit power from the low speed rotor to the high speed generator. Gearbox failure is a major issue causing high maintenance costs. With a superior power to weight ratio, a hydrostatic transmission (HST) is an ideal candidate for a wind turbine drivetrain. HST, a continuous variable transmission, has the advantage of delivering high power with a fast and accurate response. To evaluate the performance of the HST wind turbine, a power regenerative hydrostatic wind turbine test platform has been developed. A hydraulic power source is used to emulate the dynamics of the turbine rotor. The test platform is an effective tools to validate the control strategies of the HST wind turbine. This paper presents the high fidelity mathematical model of the test platform. The parameters of the dynamic equations are identified by the experiments. The steady state and transient operations results are compared with the experimental data. The detailed control architecture of the start-up and shut-down cycle is described for the test platform. 

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3. Improved analytic model for eddy current force considering edge-effect of a conductive plate

   https://doi.org/10.1109/ICELMACH.2016.7732616  

   Paul, S.; Bird, J. Z. (September 2016, Improved analytic model for eddy current force considering edge-effect of a conductive plate)

   The eddy current induction in a conductive medium with finite width and thickness due to a moving magnetic rotor is studied. The presented formulation is based on the second order vector potential and the magnetic scalar potential and takes into account the magnetic field interaction through the edges of the conductive medium. The eddy current fields as well as thrust, lift and lateral force created by the rotational motion of the magnetic rotor have been computed and the accuracy and computation time have been compared with steady-state and transient finite element analysis results. 

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4. A 3-D analytical model of a Halbach axial magnetic coupling

   https://doi.org/10.1109/SPEEDAM.2016.7525881  

   Li, Kang; Bird, Jonathan Z. (June 2016, 2016 International Symposium on Power Electronics, Electrical Drives, Automation and Motion (SPEEDAM))

   This paper derives the closed form 3-D analytical torque equations for an ideal radial Halbach rotor magnetic coupling. The performance of the radial Halbach coupling is then compared with an ideal axial Halbach rotor coupling. The closed form equations and comparison gives insight into the upper torque density limits of Nd-Fe-B based magnetic devices. 

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5. A Review of Segmented Stator and Rotor Designs in AC Electric Machines: Opportunities and Challenges

   https://doi.org/10.3390/eng6010007  

   Khoshoo, Bhuvan; Aggarwal, Anmol; Foster, Shanelle (January 2025, Eng)

   The use of segmented stator and rotor designs in AC electric machine construction offers several significant advantages, including a high-copper fill factor, increased torque density, improved field-weakening performance, simplified manufacturing processes, and enhanced mechanical strength. Additionally, segmented designs allow for the incorporation of oriented steel—either partially or fully—which exhibits excellent magnetic properties in the rolling direction, resulting in more efficient machine performance. However, lamination segmentation also introduces challenges. Parasitic air gaps between segments and an increased number of cut edges in the assembled stack can alter the magnetic properties of the machine, potentially leading to degraded performance. Furthermore, the use of oriented steel remains complex, as its highly nonlinear magnetic properties vary depending on the direction of the magnetic flux. This paper reviews the widely adopted stator and rotor segmentation techniques available in the literature, discussing their potential benefits and limitations. It also covers key aspects such as popular manufacturing approaches, the impact of segmentation on machine performance, advanced finite-element analysis (FEA) techniques for numerical modeling, and experimental methods for evaluating the performance of segmented stator and rotor constructions in AC machines. By addressing these areas, this work provides a comprehensive resource for machine designers seeking to develop AC machines with segmented stators and rotors. 

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