Dynamic Analysis and Detection of the Stator Wedges' Looseness of Large Generators

Stator bars of large generators suffer from alternating electromagnetic force during normal operation,which leads to the abrasion of the main insulation of the stator bars and finally to decreased insulation properties.Stator wedges and ripple springs are commonly used to fix up the stator bars.However,because of the long-term vibration of the stator bars,stator wedges inevitably become loose.Detection of the looseness levels of the stator bar fixtures is of great importance.In this paper,a dynamic method to detect the looseness levels of the stator bar fixtures was shown,which indicated the deformation of the ripple springs by measuring the rebound speed of the impact body that was hit on the stator wedges.Furthermore a wave mechanics model based on the fixture structure of the stator bars was introduced and the principle of the detection method was studied.Dynamic experiments of ripple springs with different deformations were conducted and the correctness of the theory and the feasibility of the detection method were verified.Finally,error factors influencing the detection method were analyzed and the accuracy of the measurement was calculated.