The Use of an Electromagnetic Finite Elements Package to Aid in Understanding Shaft Voltages in a Synchronous Generator

The shaft voltage of a synchronous generator has been simulated in a transient 2D finite element methods (FEM) package. It is not only shown that it is possible to accurately simulate the shaft voltage but that the key way and weld recesses in the stator laminations are major causes of the shaft voltage in this machine. The effects of the key way and weld recesses on the shaft voltage are individually investigated by modelling them each separately in the finite element (FE) model. Thus suggestions to aid machine designers in keeping shaft signals as low as possible are made. It is also shown that it is possible to simulate search coils in the FE package. Measurements of the shaft and search coil voltages are presented.