Analysis of Inter-Turn Insulation of High Voltage Electrical Machine by Using Multi-Conductor Transmission Line Model

In this paper, the inter-turn insulation of stator winding is comprehensively discussed. An equivalent circuit model and a multi-conductor transmission line (MTL) theory are established for the inter-turn voltage evaluation under the switching-impulse voltage, respectively. The distributed inductances are calculated by using small-signal analysis in finite element method (FEM) and the ac resistances of coils are analyzed considering the skin effect. The distributed capacitances of the coils are determined by using both electric field FEM and analytic equations. The electric potential distribution of inter-turn is calculated by the above two methods. The incident and reflect voltages are calculated by using the MTL model. The electric field of inter-turn calculated by using the FEM is presented. The FEM is used for the calculation of the inter-turn electric field distribution. The position where the inter-turn insulation may be more prone to breakdown is determined according to the result. Finally, the impact factors of inter-turn insulation including insulation materials and positions of failure in winding are analyzed in detail.