Impact of Torsional Vibration of Brushless Excitation Turbogenerator Shafting on the Parameters of Coaxial Exciter

The low-frequency oscillation of large generators poses great harm to the shaft system. In the case of brushless excitation turbogenerators, the oscillation will affect the coaxial exciter. In this article we focus on the impact of the low-frequency oscillation of large-scale generator shaft system on the coaxial exciter parameters. Starting from the influence of oscillation on the conduction law of the armature winding, the expression of the armature current was derived, and the expression of the armature magnetic field was further extracted to predict the harmonic characteristics in terms of excitation current. Simulation verification was implemented on an 8-pair pole 3-phase brushless exciter, and the experimental verification was completed on a 7-pair pole 3-phase brushless exciter. The research indicates that the specific frequency harmonics in the excitation current of the brushless exciter can be utilized to monitor the torsional vibration of the turbogenerator shaft system.