Calculation And Analysis Of Multi-Phases Fields In Synchronous Generator In The State Of Balance And Unbalance

Turbo-generator generally withstands three-phase balanced loads, but in the power operation, there will be three-phase unbalanced loads. When generator is running withstanding asymmetric loads, magnetic field produced by positive sequence current in the stator windings is the same speed and direction to the magnetic field produced by rotor rotating. But the magnetic field generated by the negative sequence current is the opposition speed and direction to magnetic field generated by rotor rotating. In this way, 2 octave synchronous speed which is relative to the speed of the rotor induces eddy currents and heat in the various parts of the surface of the rotor. For some problems of the turbo-generator running in the negative sequence operation, in this thesis, some contents are listed as follows:Firstly, when the rotor slot wedges materials are different, the loss density produced by the negative sequence current in the rotor various parts is comprehensively analyzed and calculated; In order to study the role of polar wedge, loss density produced by the negative sequence current in the rotor various parts is calculated when the rotor pole face is with or without slot wedge. The conclusions are that different materials and pole face with or without slot wedge affect the loss distribution and size in rotor.Secondly, loss density was obtained in electromagnetic field as heat source. Section of the rotor is the solved region and establish two-dimensional numerical model. Temperature field is calculated.The temperature distribution in the solved region is obtained when the rotor slot wedges are different materials and pole face with wedge. At the same time, the rotor temperature field is calculated when the pole surface without wedge.The result shows that different characteristic of materials and pole face with wedge or without wedge have an influence on the temperature fields under negative sequence operating.Besides that, electromagnetic fields are determined using the iterative approach under two structures of stator windings and the load operation. And the radial flux is analyzed along the stator inner circle into the stator teeth and slots; And parameter of machine is calculated such as unsaturated synchronous reactance, saturated synchronous reactance and direct-axis transient reactance under the two structures of the stator windings. The value of direct-axis transient reactance is calculated under rotor winding imposed or not imposed constraints; Using finite element method, calculation of the power generator, parameters and power angle are obtained in the ultra-fat state under the two structures of the stator windings. The results show that different structures have a little influence on electromagnetic parameters value.Analysis method in this paper can be directly used for other types of turbine-generator.