The Measurement And Simulation Of Laminated Core Magnetic Properties

As very important primary electrical equipment in the power system,the transformer has a history of more than 100 years.It has reached a very high level in theory and manufacturing.Its safety and stability is essential for the normal operation of the power system.In recent years,with the increasing construction of large power grid and UHV power grid,more and more larger capacity generators and transformers need to be put into the power grid.Compared with the world advanced enterprise,the research on the basic problems such as the design rules,safe operation and performance optimization of UHV and high capacity transformers is still lagging behind in our country.Sponsored by the National Natural Science Foundation of China under grant 1206115011019 and 51577066,this article carry out the work from the following three aspects:(1)Based on the national standard GB/T3655,the precision instruments is used for the purpose of improving the measurement accuracy and the electromagnetic properties of silicon steel sheets with the same brand of different manufacturers were measured and compared by using the Epstein square,which provides more accurate material properties for the no-load simulation of transformer core.Based on the present situation that the performance of silicon steel sheet is difficult to be evaluated,a method of measuring saturation point is proposed;According to different characteristics of silicon steel sheet and laminated core,the loss coefficient of different silicon steel sheet is studied to provide the basis for the correction of simulation modeling.(2)On the premise of the accurate calculation of the no-load current of the transformer,an algorithm for no-load loss of transformer core based on the loss separation model is proposed based on the principle of three-dimensional electromagnetic field calculation and the principle of field circuit coupling.Compared with the existing three algorithms,the simulation results show that the proposed method is the most close to the measured value.(3)Based on the similarity theory,the similarity relationship between the original model and the reduced ratio model of the transformer core is derived and verified by a simple 180 turn transformer;the simulation results of the scaled model are extended to the actual model of the UHV Transformer core.The electromagnetic field distribution of single phase three column two frame core is studied,and the transformer core of different materials is evaluated based on the previous loss algorithm.