Research On Calculation And Measurement Of Strand Current In Stator Transposition Bar For Large AC Generator

To effectively improve the distribution of strand current,the stator bar adopts transposition technique in large AC generator.The accurate calculation of strand current in stator transposition bar is the theoretical guarantee for the transposition design of the stator bar,and the accurate measurement of strand current is the practical guarantee.The stator incomplete 360° transposition bar is taken as the research object,and the relevant research work that is calculation and measurement of strand current in stator transposition bar is carried out.Aiming at the theoretical calculation method of strand current in stator transposition bar,a field-circuit coupling method which combines the finite element method with the equivalent circuit is put forward.According to the structure characteristic of transposed strand in slot and strand in end,the three-dimensional physical model and the numerical model of stator 308.57° transposition bar are established,and the mathematical model and boundary condition of the solution domain are given.Meanwhile,the equivalent circuit of stator 308.57° transposition bar is established,and strand current is directly obtained by the field and the circuit.In view of the experimental measurement method of strand current in stator transposition bar,a method of obtaining strand current by measuring the leakage magnetic field near the end is proposed.In line with the structure characteristic of strand in end,the topological structure about Hall measurement is built and the correlation equation between the strand current and the leakage magnetic field measured by Hall element is obtained.Additionally,a kind of linear array Hall sensor structure is designed and the process of all the sensitivity coefficients is given.Meanwhile the hardware and software are designed in large AC generator.The hardware consists of power platform,stator transposition bar platform and strand current measurement platform,and the software mainly completes two-part work that are to collect sensor signals and write handler about calculating strand current.The measurement system of stator 308.57° transposition bar is built by measurement method and measurement system,and the specific steps of measuring strand current is given.Thus the leakage magnetic field at the end is measured,and strand current is obtained by using the correlation equation.By comparing the experimental results and theoretical analysis results,the validity and correctness of measurement method for strand current in stator transposition bar are verified.