Analysis On1200MW Generator Negative Sequence Operation Capacity Based On Ansoft And Workbench

Turbo-generator generally withstands three-phase balanced loads, but inthe power operation, there will be three-phase unbalanced loads. Whengenerator is running withstanding asymmetric loads, magnetic field producedby positive sequence current in the stator windings is the same speed anddirection to the magnetic field produced by rotor rotating. But the magneticfield generated by the negative sequence current is the same speed andopposition direction to the magnetic field generated by rotor rotating. In thisway, magnetic field produced by negative current is two times synchronousspeed which is relative to the speed of the rotor, it could induce eddy currentand heat in the various parts of the surface of the rotor. Therefore, thenegative sequence capacity analysis of turbo-generator both contains theeddy current field and the temperature field, which is a multiple physicalfield problems with electromagnetic-thermal coupling.Each material has its own limit temperature, the generator negativesequence capability is evaluated by rotor material on the temperature, whilethe temperature is caused by the eddy current loss under negative sequencemagnetic field. This paper takes1200MW turbo-generator of ShanghaiElectric Power Generation Equipment Co.，Ltd, Generator Plant as researchobject, by using the method with Ansoft software and Workbench platform,some contents are researched as follows:Firstly,2D models of tooth-part and passing-hollow-part of1200MWturbo-generator are created. To examine the effect of rotor slot wedge anddamping slot wedge, the eddy current loss density of components of rotor are calculated respectively under three kinds of cases with the slot wedge and damping slot wedge existence or not. The result shows that, the existence of the slot wedge and damping slot wedge has great effect on the density of the eddy current loss of the rotor parts. At the same time, the CAD software to calculate2D negative sequence eddy current field of turbo-generator is developed by Visual Basic language, the interface between Visual Basic and SolidWorks&Ansoft is researched in detail, and completed their seamless link. What’s more, the solve function about modeling and finite element analysis of CAD software in one-click is come true.Secondly, based on the calculation of2D negative sequence eddy current density of turbo-generator,3D solid model of1200MW turbo-generator is built. And considering the slot wedge and damping slot wedge on the influence of the eddy current loss, the value and distribution of the3D eddy current loss of generator are analyzed. As can be seen from the calculation results, Slot wedge especially the presence of damping slot wedge can effectively reduce rotor negative sequence eddy current loss value when generator is under negative current.In the final, taking the eddy loss which calculated in3D electromagnetic field as a heat source, selecting the3D entity model of rotor as numerical model, The rotor steady state and transient negative sequence temperature field are calculated. For rotor body with and without slot wedge and damping slot wedge, the solved area steady state and transient temperature distribution are obtained. Calculations show that turbo-generator can satisfy the steady state and transient negative sequence runtime material temperature limit when it installing damping slot wedge.Analysis method in this paper can be directly used for other types of turbo-generator.