Research On Stator Transposed Winding And Its Electromagnetic-Thermal-Force Characteristics In Large Induction Machine

As the carrier of electric load,the design of stator winding in large AC motor directly determines the motor capacity,technical performance and manufacturing cost.The transposition technology of stator winding is the key technology to reduce the AC loss of electrical machine,and the transposition technology is different for different types of electrical machines.The stator winding of large induction motor adopts a formed multi-turn coil structure.Each half turn coil has a small number of strands and a short axial length.Therefore,the difficulty of transposition technology is significantly increased.In traditional design method,the winding straight region is not transposed,but the end is twisted.How to improve the transposition technology and break through the original transposition method has become the bottleneck problem of increasing the electromagnetic load and reducing the winding loss and temperature rise of electrical machines.Therefore,this dissertation studies the stator transposed winding and its loss,temperature rise and electromagnetic force of large induction motor.The design idea and transposition rules of the single strand transposition technology of induction motor stator are presented in this dissertation,which presents the arrangement structure and transposition method of the odd number strands.Based on the single strand transposition technology,the stator winding transposition method in the slot and the connection mode of the end are studied.The influence of transposition angle,extended transposition length and R and T connection mode on circulating current loss of stator transposed winding is analyzed.The quasi global transposition method and global transposition method of stator winding are proposed,which can effectively reduce the circulating current loss.The advantages of the proposed transposition technology are verified by comparing with the stator winding with Robel transposition technology.The calculation and analysis method of stator winding circulating current loss is an important method to evaluate the design of stator winding transposition.Combined with the leakage of magnetic field in the stator winding,the equivalent circuit network model is proposed to calculate the circulating current loss of the stator transposed winding.Considering the influence of transposition structure on the resistance of stator transposed strands,the full path simulation calculation method of slot leakage reactance of the transposed strand,the piecewise linear calculation method of end leakage reactance and the lumped parameter calculation method of harmonic leakage reactance are proposed,which realize the real simulation of transposition path of stator winding strands.The experimental test system of the strand current is built to verify the rationality and feasibility of the circulating current loss calculation method of the stator transposed winding,which consists of the power system,the stator transposed winding and the strand current measurement module.The equivalent thermal circuit network model of temperature rise of induction motor stator transposed winding is established.The heat source change of strand caused by transposition structure and the heat source change of stator core caused by spatial position are fully considered.A method is proposed to simulate the transposition path of stator winding,which combines the solving region discretization of the delayed transposition simulation and changing the thermal conductivity connection path of strand node.The calculation method of thermal resistance parameters between different materials is given,which provides a fast and feasible analytical algorithm for the calculation of temperature rise of stator transposed winding.By calculating the stator temperature rise of induction motor,the temperature rise distribution law of stator transposed strand,stator core,stator shielding and other parts is obtained;otherwise,the hottest temperature and its location are determined.The validity of the equivalent thermal circuit network method of the stator transposed winding is verified by the temperature rise test of the real electrical machine.The electromagnetic force distribution of stator winding with transposition structure is also one of the important factors in transposition design,especially the electromagnetic force of stator transposed winding will directly affect the stability of windings under fault conditions.In this dissertation,a three-dimensional field circuit coupling numerical analysis method for electromagnetic force of stator transposed strand is proposed,which reveals the influence of short-circuit faults of different strands on the strand current and the end electromagnetic force.The results show that the strand short-circuit fault has a significant effect on the short-circuit strand current and electromagnetic force density.In the case of short-circuit fault between strands in the same row at the non-transposition bend,the current jump degree and the end electromagnetic force density of the short-circuit strands are larger.In the case of short-circuit fault of strands in the same column at the non-transposition bend,they are smaller.In the case of short-circuit fault between strands at the transposition bend,they are in the middle.The current jump degree of strands decreases gradually from the stator slot opening to the slot bottom.The current of non-short-circuit strands and the electromagnetic force density at the end are less affected by the short circuit fault of strands.