Study on the influence of three-phase voltage unbalance on electromagnetic performance and vibration of high-voltage line-start permanent magnet synchronous motor

Since the operation of the high-voltage line-start permanent magnet synchronous motor (HVLSPMSM) does not need the control circuit and is directly powered by the grid, its operating stability is easily affected by the three-phase voltage unbalance. Thus, a 10 kV, 630 kW motor is taken as an example to study the impact of voltage unbalance on its electromagnetic performance and vibration. First, the effect of voltage unbalance on the torque performance of the motor is investigated using the finite element method (FEM), and the variation rules of torque ripple and torque harmonic frequency with voltage unbalance degree are obtained. Then, the analytical expressions of radial electromagnetic force (REF) under normal and unbalanced voltage conditions are derived, and the rules of electromagnetic force variation of different orders and frequencies under rated load and unbalanced voltage conditions are determined, and the analytical results are verified by finite element results. Finally, the motor vibration response characteristics caused by three-phase voltage unbalance are obtained by using modal analysis and vibration harmonic response analysis. The results indicate that the vibration performance of the motor is significantly affected by the threephase voltage unbalance. When the voltage unbalance degree is 6%, a vibration acceleration amplitude of 800 Hz and 900 Hz increases by 18.03% and 78.57%, respectively.