Order feature analysis for torque ripple of permanent magnet synchronous motor for an electric vehicle

Torque ripple of permanent magnet synchronous motor (PMSM) causes body structural vibration and noise in an electric vehicle. Here, firstly the dynamical and high order torque signals of PMSM were measured, their order features were revealed and analyzed. Then, a mathematical model of torque ripple in PMSM considering non-sinusoidal magnetic field distribution and slotting was built. Orders and frequencies of torque ripple were predicted and then the rotating speed criterion for measuring dynamical and high order torque signals was presented. Both test study and theoretical study showed that torque of PMSM has a feature of order ripple and the main orders are the (h-1)^th orders, the 2(h-1)^th orders, the (6i+h-1)^th orders and the (6i+h-1)^th orders (h∈N; i∈N); the h^th order current causes the (h-1)^th order and the 2(h-1)^th order torque ripple; the hth order current, non-sinusoidal magnetic field distribution and slotting cause the (6i+h-1)^th order and the (6i-h+1)^th order torque ripple.