A novel half-type permanent magnet structure of IPM BLDC motor

Conventional Interior Permanent Magnet (IPM) Brushless DC (BLDC) motors use an array of alternating N and S pole Permanent Magnets (PM) in the air gap of the motor. This paper proposes a novel half-type IPM BLDC motor which uses only N pole PMs. By designing the half-type IPM BLDC motor, we were able to successfully reduce the amount of permanent magnets by 24 % while maintaining important characteristics such as torque, output power and efficiency. Unlike Surface Permanent Magnet (SPM) BLDC motors, there is almost no literature on half-type IPM BLDC motors since it is very complicated to reduce torque ripple and consider permeance of the magnetic circuit. However, we were able to reduce the torque ripple to that of conventional IPM BLDC motor levels. Initial model analyses were carried out by Finite Elements Method (FEM) and then verified through experimental evaluation with a prototype.