Effects of damper winding, eddy current, and leakage flux on magnetic field distortion and stator electrical quantity research of nuclear power turbo‐generator under external asymmetry

Abstract

One phase overload or lightload condition is a very common condition in nuclear power turbo‐generators, and magnetic field distortion and current asymmetrical degree concern the safe operation of turbo‐generators. Damper and wedge windings are the special parts that distinguish the nuclear power generators from other smaller generators. Therefore, it is extremely important to investigate magnetic field distortion and stator electrical quantity. At the beginning, taking saturation and slot effects into account, the finite element model of a 1400MVA nuclear power generator is built up. And through comparison between the finite element simulation and the experimental results of no‐load characteristics and short‐circuit characteristics, the effectiveness of the finite element model was fully tested. Then, with or without damper and wedge windings, and leakage flux, the negative sequence equivalent circuit is employed to explain the law of magnetic field distortion under stator negative current, which is also verified by finite element simulation. Based on a novel theory proposed in this article, the law of the stator positive and negative sequence current, and the current asymmetrical degree with alteration of one‐phase load under steady state are given in detail. Additionally, the finite element method is developed to test the correctness of the novel theory. The influence of damper and wedge windings, leakage flux at coil ends, and eddy current on the solid magnetic‐pole of rotors on stator electrical quantity is also discussed in detail. © 2019 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.