Theoretical Research On Branches Asymmetric Stator Winding Of Large Hydro-generator

In theory, the hydro-generator stator winding of any speed can be designed symmetrically. Considering synthetically the restrictions of the hydrological condition and the voltage level of electric power system in practical application, it is not always ideal to adopt hydro-generator of symmetrical stator winding. The hydro-generator with asymmetric branches stator winding, which it is not at the best operating point, can bring facility to rational design of the generator units. With the development of power industry and the growth of unit capacity, the large capacity hydro-generator whose stator winding is asymmetrical has appeared. When branches of winding are asymmetric, the electric potential, current and impedance of branches winding will be different. The research on the influence of the especial asymmetric winding on electric machine operating characteristic should go farther. When the short-circuit takes place within stator winding, the short-circuit currnet may exceed several times of the largest current, concequently, it will cause serious electrical damage, mechanical damage and thermal damage. So, it is important to study the stator asymmetrical winding, to clarify the influence of the especial asymmetric winding on electric machine operating characteristic, to design relay protection that can lighten the danger.For a large hydro-generator, at first, the asymmetric branches connection of hydro-generator stator winding is analyzed. An asymmetric branches winding connection method is put forward. After analyzing the branches EMF asymmetrical degree, a standard is brought forward. We can know which winding project is the best by the standard. On this basis, to discuss the calculation problem of asymmetric branches stator winding parameters, according to the multiloop theory of electrical machine, a mathematical model of asymmetric branches winding parameter calculation is set up in the paper, a universal method by which asymmetric branches winding electromagnetic parameters can be calculated is given. Analysis indicates, the method can be used in the calculation of electromagnetic parameter of any windings and the result is accurate.