Industrial-scale motor cogging torque control for a high-volume motor manufacturing

Rare Earth Permanent Magnet (REPM) motor acoustics plays an increasingly important role in automotive mechatronic components and systems, due to more vehicle electrification and ever-increasing market demand. A large number of factors affect PM motor acoustic behavior. One of major contributing factors is the motor cogging torque. This paper reports industrial practice and control of motor cogging torque level which must meet a high-demanding technical specification. Since there exist a wide spectrum of motor slot and pole number combinations with varying permanent magnet structures, 9-slot and 6-pole Surface-mounted PM (SPM) topology has been investigated in great details. It is found that permanent magnet rotor field quality has a sensitive and significant impact on the RE SPM cogging torque level during the high-volume motor manufacturing. With right diagnosis and analysis tool, rigorous specifications of active materials in particular PM, and manufacturing process, the cogging torque level can be reduced and controlled.