Low-speed high-torque machines are being increasingly used in various applications such as electric vehicles, wind-power generation, electric vessels, industrial robots, and home appliances, because they can offer direct-drive operation, which avoids the inconveniences of mechanical gearboxes. The magnetic geared permanent magnet (MGPM) machine, which works similar to an electrical machine coupled with a coaxial magnetic gear, can be used as a substitute for direct drive systems and mechanical gears. The MGPM machine is gaining interest owing to its significant features, such as reduced acoustic noise, maintenance-free operation, improved reliability, precise peak torque transmission capability, and inherent overload protection. In addition, an MGPM machine can further reduce the overall size and weight, compared to the simple combination of gear and electric motor. Despite these advantages, it is difficult to gain insight into the influence of the design parameters on the electromagnetic performance of MGPM machine. Analytical methods are useful for the first evaluation of machine performances and for design optimization, because continuous derivatives, which are obtained from the analytical solutions, are required during most optimization methods. In this paper, an analytical solution based on a Fourier analysis is proposed to compute the on-load electromagnetic performance in magnetic-geared permanent-magnet machines. The analytical solutions are derived by solving the field-governing equations in each simple and regular subdomain, i.e., permanent magnet, air, modulation slot, slot opening, and slot, and then applying the boundary conditions to the interfaces between these subdomains. Based on these solutions, the electromagnetic performance is determined analytically. All analytical results were extensively validated using nonlinear two-dimensional finite element analysis and experiments. Using the proposed method, we investigated the effect of the slot number on operating characteristics. The proposed method could be very useful in the initial design and optimization of a magnetic-geared permanent-magnet machine.
|Submitters Country||Republic of Korea|