Electromagnetic Parameter Calculation And Transient Performance Analysis For Large Turbogenerator

With the unit capacity increase of turbogenerator and rapid development of computer technology, the electromagnetic field numerical computation method (EFNCM) has been applied deeply and widely in the design of turbogenerator. As a beneficial supplement of tradition magnetic circuit calculation of turbogenerator design, the EFNCM have played an irreplaceable role in some special problem’s analysis. Based on the magnetic circuit analysis and numerical calculation of electromagnetic field, the calculating method for electromagnetic parameter of turbogenerator was studied, and the asynchronous operation capacities after direct short-circuit excitation-loss of turbogenerator were researched.Firstly, in view of the common used electromagnetic design formulas of the large turbogenerator in China has large error, and they do not considered the effects of small slot and bias slot of the rotor of the turbogenerator. So the calculating formulas of magnetic circuit are derived drawing on the design ideas of the rotor magnetic circuit of the U.S. Westinghouse. And the accuracy of the revised electromagnetic design formulas is verified by using finite element method. The revised magnetic circuit design formulas can be fully considered the effects of small slot and bias slot of the rotor of the turbogenerator, and they can be used in the four-pole turbogenerator design.Secondly, the rated fields current, the iron loss and reactance parameters of turbogenerator are calculated by magnetic circuit calculation formula and finite element method, respectively. When calculating of rated fields current of turbogenerator, the2-D field-circuit-motion coupled finite element and the equivalent load impedance method (ELIM) combined mathematical model for large turbogenerator are established. At the same time, the calculating principle and approach of the ELIM are also proposed. Based on the2-D transient field calculation results, the iron loss of the turbogenerator under rated load with non-sinusoidal magnetism flux density waveforms and rotating magnetic field considered and the3-D loss density distribution map are got using field-circuit combined method and harmonic analysis method, respectively, after analysis of magnetic density variation laws of key points on the stator core.Finally, based on2rd order Park model and2-D field-circuit-motion direct coupled finite element model respectively, the asynchronous operation capacities after direct short-circuit excitation-loss of the turbogenerator under different loads were researched. The parameters such as stator terminal voltage, stator current, rotor current were obtained after direct short-circuit excitation-loss of the turbogenerator under different loads were analyzed. Moreover, the distribution of electromagnetic field in turbogenerator was analyzed. The results can provide an important theoretical foundation for large turbogenerator’s design and asynchronous operation capacity analysis.