Numerical Calculation Of Synthesis Physical Fields Of Large Hydrogenerator

The practical running of large salient synchronous generator is a very complex physical process. To describe this physical process exactly it is necessary to analyze it from the angle of coupled fields including electromagnetic fields and temperature fields. Because insulation layers in strands and turns are very thin, they are always be out of consideration when calculating electromagnetic fields. But the whole areas of stator strands insulation may exceed that of one piece of strand and it will have certain of effect on the calculation precision. The same condition occurs for the turn insulation. Therefore, calculation of the air gap magnetic field and rotor surface losses and comparison of the calculated result with and without the consideration of the stator strands insulation and rotor turns insulation will have reference significance for designing machine accurately. Also the insulation layers are always ignored in the calculation and analyze of hydrogenerator. However even a thin insulation layer may have a significant temperature drop and this will have a direct effect on the machine design.According to the theory of electromagnetic fields and temperature fields, the distribution of electromagnetic fields and temperature fields of the large salient synchronous generator with fractional stator slot are calculated and analyzed by the Finite Element Method (FEM) in this paper. There is a significant temperature drop in insulation layers in stator and rotor of generator. Calculating results with and without the consideration of insulation is compared and the effect of insulation to the air gap magnetic field and rotor temperature field is analyzed. Longyang Gorge 320MW hydrogenerator is taken for example and the calculating results and the measured results are compared to test the accuracy of calculation.