Model for Nonlinear Electric Field Control in End-Winding Region of an Electrical Machine

The electric potential at the surface of a stress grading system (SGS) of an electrical machine is estimated analytically by means of a new one-dimensional model approach. The analytical tool is presented for electric field grading materials (FGMs) having power-law field-dependent conductivity, field independent conductivity, and field independent permittivity terms as dielectric parameters. The model-calculated data are compared with finite element results for SGS with 15 distinct FGM options that are used in SGSs of medium voltage motors or generators. The results indicate that the analytical tool is suitable for the basic analysis of electric field in an electrical machine end-winding region both during sinus and pulse voltage conditions.