Optimal design of a surface mounted permanent-magnet BLDC motor for spacecraft applications

This paper presents the optimal design of a surface mounted permanent-magnet (PM) Brushless direct-current (BLDC) motor meant for spacecraft applications. The spacecraft applications requires the choice of a motor with high torque density, minimum cogging torque, better positional stability and high torque to inertia ratio. Performance of two types of machine configurations designed viz Slotted PMBLDC and Slotless PMBLDC with Halbach array and radial magnetization are compared with the help of analytical and finite-element (FE) methods. It is found that unlike a Slotted PMBLDC motor, the Slotless type with Halbach array develops zero cogging torque without reduction in the developed torque, suiting spacecraft applications. Moreover, the machine being coreless provides high torque to inertia ratio and zero magnetic stiction confirming to the requirements of spacecraft applications.