Shaft torsional oscillation of induction machine including saturation and hysteresis of magnetizing branch with an inertia load

This paper describes the torsional oscillation phenomenon occurring in a multiple winding induction machine. It includes the effects of nonlinearity and component interactions between driver and inertia load through mass spring coupling system under starting transient disturbance. The model fidelity is evaluated from the foreseen torsional torque of the motor driving system by several excitation sources. Steady state and transient analysis are presented to show the significant influence of the magnetizing branch nonlinearity on the torque oscillation for an induction machine with sinusoidal or pulse width modulation (PWM) inverter excitation to drive inertia load. Simulation results and fast-Fourier-transform (FFT) analysis demonstrate that not only can the torsional oscillation amplitude be reduced, but the system dynamic performance is also improved through a multiple terminal inverter feeding with proper displacement angle between stator winding sets. In addition, starting process analysis shows that the torsional oscillation components can be substantially reduced by the selected starting methods with proper switching coordination. The risk of premature component failure due to the excess of the designed limit for dynamic torsional stresses can also be diminished