Developing a Numerical Model for Optimization of a Coaxial Magnetic Gear

Magnetic gears have in recent years attracted a lot of interest as a potential replacement for mechanical gears in applications requiring high torque and low speed. Since the two shafts are not in direct contact undesirable side effects such as friction, noise and vibration are eliminated. This paper concerns the optimization of a coaxial magnetic gear. The problem is solved using a numerical tool, COMSOL Multiphysics, which utilizes finite element analysis to solve the physical model. An optimization toolbox is available in the software, which has been used for the synthesis of the problem. Effort is made to model the entire problem, including losses and optimization, without the use of an external programming software. The resulting model offers a large variety of objectives and constraints, making it useful in a wide range of applications. Losses in iron are estimated using a Fourier transform to obtain all harmonic contributions. However, due to a clear mismatch between the Fourier transformed signal and the original time signal, the validity of the iron loss calculations has been drawn into question. Eddy current losses in permanent magnets are calculated numerically, and show that temperature rise in the magnets pose a serious threat if no action is taken to reduce the circulating currents