Leakage Inductance Calculation And Magnetic Structure Design Of High Frequency Isolation Transformer

High frequency transformer is a kind of small transformer which realizes electrical isolation and energy transformation through power electronic technology and high frequency flux technology.Compared with the traditional power frequency transformer,HFT has the advantages of small volume,light weight,low cost,high power density,so it has a wide range of applications in power electronic transformer,UPS,switching power supply,new energy power generation,electric vehicle and other fields.However,due to the higher operating frequency of HFT and the fact that HFT is mostly used in converter circuits,the characteristics and design of HFT are quite different from those of traditional power frequency transformers.The leakage inductance that can be ignored for low-frequency transformer have become the key parameters of HFT performance,and have a significant impact on the stability of the working circuit.Therefore,the analysis of the influence of high-frequency effect on the electromagnetic parameters of the transformer core and winding,and the study of the calculation theory,regulation technology and design method of HFT leakage inductance have become the key issues in the current HFT research field.In this paper,aiming at the problems of large calculation error and small adjustment range of HFT leakage inductance parameters in actual engineering design,the leakage inductance calculation and magnetic structure design of HFT were studied.The main work is as follows:(1)The equivalent circuit model of distribution parameters of high-frequency transformer is established.The method and principle of calculating HFT leakage inductance in different occasions are introduced.The influence of skin effect and proximity effect on the electromagnetic parameters of transformer winding is analyzed,and the calculation formula of AC resistance is summarized.The influence of high frequency effect on core loss of transformer is analyzed and the choice of core material is discussed.(2)Based on the classical distribution model and the actual distribution model,the simplified calculation formula and accurate calculation formula of HFT leakage inductance parameters are derived.Based on the flux partition,area compensation and flux grouping,an improved calculation method of HFT leakage inductance of complex winding structure considering frequency variation is proposed.Thesuperiority of the new method is proved by the calculation,simulation and measurement comparison experiments.(3)Three HFT prototypes with different structure are designed and manufactured,and a three-dimensional simulation model is established according to the parameters of the prototype.The HFT experimental measurement platform is built to measure the electromagnetic parameters of winding,core and prototype.The frequency dependence characteristics is analyzed,and the accuracy of HFT computational model is verified.(4)Based on HFT simulation model,the influence of winding structure and magnetic structure on transformer leakage inductance is studied.In this paper,a design scheme of the magnetic structure of the winding is proposed,which can adjust the leakage inductance parameters greatly by combining interleaving and magnetic guide plate.