Research On Strand Current Calculation And Measurement Of Stator Multi Transposition Bar For AC Machine

AC machine is an important equipment in electric power production.Along with the development in electric power production field,the capacity of AC machine is required more and more big.The local temperature of the stator bar is too high due to the circulating current loss increase for the stator bar.However,stator bar turns and transposition technology can effectively improve the distribution of strand current and inhibit the circulating current between strands.Accurate calculation and test of the strand current in stator multi-turn transposition bar is the key to verify the effect of transposition technology on the inhibition of circulating current.In this paper,the stator slot department for 3480 transposition and the end without a transposition for the three-turn bar as research object.Using simulation and experiment testing scheme studies strand current of the stator three-turn transposition bar.According to the structural characteristics of the stator bar,the three dimensional physical model and simulation model of the multi-turn transposition bar in the AC motor are established.The mathematical model and boundary conditions of the solution domain are given.Aiming at the network topology of stator winding transposition type,the calculation formulas of strand current and circulating current are deduced.The field-circuit coupling finite element method is used to calculate the current distribution of the stator multi-turn transposition bar.An experimental testing system for the stator multi-turn transposition bar of the AC motor is built,which mainly includes a power supply platform,a stator multi-turn transposition bar platform and a strand current testing platform.Proposed the open and closed current transformer test method and the hall current sensor test method and given the structure and working principle of the two kinds of sensors.The correlation equation between the strand current and the magnetic field around the strand is established and specific steps of measuring strand current are given.By using these two test methods respectively,testing the strand current distribution of the same stator multi-turn transposition bar.Finally,the circulating current between strands is calculated.The test results of the two experimental methods and simulation results are compared and analyzed respectively and determine the error between the experimental results and the simulation results.The accuracy of the two methods is analyzed.