Design Modeling and Prototyping of a 55 Watts Surface Mounted PM Machine With High Torque and Low Torque Ripple for Cooling Fan Application

This paper presents design, analytical modeling and optimization of a 55 watts, 3000 rpm surface mounted permanent magnet (SPM) machine with cubical permanent magnets (PMs) for the cooling fan application. First, the size/dimensions of the motor are laid out at the design stage to meet the specifications (e.g., rated power, speed) of the target application. Next, general performance characteristics of the designed machine are analytically predicted using a two-dimensional (2-D) hybrid analytical model. The hybrid model is composed of (i) solving Maxwell equations on a hypothetical slotless structure, and (ii) virtual magnetizing current to account for the stator slotting effects. Due to the lack of cylindrical symmetry of the given structure with cubical-shape PMs, the PM region is divided into a number of smaller segments and the calculations are carried out discretely per PM segment as opposed to the standard practice of considering the entire PM region as one subdomain. Next, the machine structure is optimized simultaneously mitigate the torque ripple and boost the torque density. The laboratory prototype of the motor is fabricated and tested to further validate the analytical model as well as the functionality of the designed motor.