The Field Current Calculation Research Of The Large Turbine Generator Based On Ansoft

With the rapid development of computer technology, the numericalcalculation method of electromagnetic field has been applied in the turbinegenerator design broadly and deeply. And as a useful supplement ofclassical magnetic circuit method, it has played an irreplaceable role. Theresearch on how to use numerical calculation method to calculate generatorfield current has been done in-depth. The influence factors of field currenthave been analyzed in details.First of all, the research status of field current calculation methods isanalyzed, and the field current calculation principles of the formulamethod、test method and numerical calculation method are introduced.Secondly, it has been analyzed that how to apply the formula methodinto the field current calculation. Onthe basis ofdetailed analysis of formulamethod, the formula method has been edited to general procedures. Besides,it has been edited to a human-machine interface in which the calculation ofthe field current can be completed. The calculation results show that theresult is much more accurate through the human-machine interface. Whenthe magnetic circuit is saturated, the field current calculation result can beused as an initial value of numerical calculation method.For the disadvantages of formula method, it has been analyzed how tocalculate the no-load and rated load field current of the turbine generatorthrough the finite element method. When calculating the rated field current,a time domain model was built. By using the method of parameter, thecorresponded voltages were got on different rotor initial positions and fieldcurrents. Then by using two dimensional interpolations which can avoid the iteration to the voltage and power factor, the field current canbe got directly.The calculation speed has been improved greatly.The field current of different turbine generators was calculated by thetwo methods. Comparing the two calculationresults withthe design value, ithas been found that the calculation result of the formula method is close tothe design value; when generator capacity is large or some specialstructuresneeds to be considered, the calculation precision of formula methoddecreases. While using the finite element method introduced in this paper,even if the field current of the million kilowatt nuclear power generator canbe calculated accurately. If some special structures need to be considered, itjust needs to take these special structures into consideration when buildingthe finite element model and the accurate can be guaranteed.Finally, through the research on the influence factor of field current, ithas been found that when the turbine generator uses closed slot the fieldcurrent is small, besides, the harmonic content of the air gap flux density isreduced. Through the study of magnetic slot wedge, it has been found thatthe effect of the magnetic slot wedge is equivalent to make the open slotbecome a closed slot, and it avoids that the gap becomes uneven. At thesame time, the field current decreases when using the magnetic slot wedge.Though the field current decreases but not too much when the turbinegenerator rotor uses the A silicon steel material. So when the customerrequirements can be met, the generator can uses the cheaper materials sothat the cost of the generator can be reduced.