Investigation on Maximum Electromagnetic Torque of Permanent-Magnet Synchronous Machines

Many application fields need motors that could output large torque in a short span of time such as missile and aircraft, but larger torque needs larger volume that could influence the system performance. Therefore, promoting the motor's maximum torque with small volume is the new challenge for motors. So, this paper presents a method for analyzing maximum electromechanical torque (with rate speed) of PMSM without the consideration of thermal effect produced by copper loss. This paper also discusses the factors that influence maximum torque of PMSM under the condition of i(d) = 0 control mode. A function between motor torque and the inner parameters is first obtained under the constraint of electrical and magnetic saturation. For verifying the accuracy of the function and its results, the characteristics of the series motors with different inner parameters that are obtained in the function are testified by finite element method (FEM) software. Finally, a prototype motor is selected to be manufactured to verify the analysis result. Based on the torque experiments result, it could verify the accuracy of the function that describes the rule of PMSM maximum torque. Based on FEM software and prototype test verifying, the method could supply the theoretical support for PMSM maximum torque design.