Electromagnetic Force Estimation by Using Strain Gauges in Permanent Magnet Motors

The concerns about the acoustic noise, vibration, and harshness of electric machines are ever-growing in traction applications for electric vehicles. Among various motor topologies, interior permanent magnet synchronous machines are adopted in most commercial products for advantages including high efficiency and high torque density. However, the severe acoustic noise and vibration excited by the electromagnetic forces acting on the stator remain an issue. In this paper, a method using strain gauges is proposed to measure the radial electromagnetic force in an interior permanent magnet synchronous machine for electric vehicle applications. The method is first verified in finite element analysis. Additionally, an interior permanent magnet synchronous motor installed with strain gauges is fabricated for experimental verification. The experiment results show that the radial force estimated by using the strain gauges has a good correspondence in terms of phase and shape, whereas a significant difference in amplitude is observed.