Abstract
Permanent magnet synchronous motor is an electromechanical coupled system. Electromagnetic field can result in change of the dynamic behaviors of the PMSM's rotor system. Here, changes to the electromagnetic torque excitation caused by the torsional displacement are considered using electromechanical coupled dynamic equations for the rotor. Steady state solutions and their stability are determined. Effects of inner power factor angle, pole pairs, saturation coefficient and torsional stiffness of shaft are investigated. Also, numerical integration is used to validate and carry out perturbation results. Based on the results, amplitude jump and bifurcation instability phenomenon can be avoided through reasonable control of permanent magnet synchronous motors, electromagnetic and mechanical parameters design and consequently control the torsional vibration of PMSM's rotor system.