Effect of Rotor Interturn Short circuit degree and position on Stator Circulating Current inside Parallel Branches in Generators

This paper presents a comprehensive analysis on the stator circulating current inside parallel branches (CCPB) under different rotor interturn short circuit (RISC) degree and positions. Firstly, based on the characteristics of the air gap magnetic field variation before and after RISC, the specific analytical expressions of the magnetic flux density (MFD), and the CCPB of the stator are derived. Then, taking the SDF-9 generator as the research object, the finite element analysis (FEA) is used to verify the circulation characteristics of the stator CCPB under different RISC degree and positions. Finally, the results are compared with the theoretical analysis, and the two changing trends are basically consistent. It is shown that the occurrence of RISC will cause even harmonic circulation components and the 2nd harmonic is the main component. As the degree of short circuit increases, the amplitudes of even harmonic circulation components of CCPB will show an increasing trend. In addition, the amplitude of the even harmonic circulation of the stator CCPB changes with position at the same short circuit degree.