| Metro locomotive adopts traction power supply mode,which takes current from overhead lines and returns to the negative bus pole of substation through running rails.Accurate measurement of traction is of great significance for evaluating the leakage of running rail return current and ensuring the safe and stable operation of metro system.Based on this,this thesis aims at developing a current sensor with high sensitivity,simple structure and suitable manufacturing cost.By means of theoretical analysis,finite element simulation and experimental test,the magnetic circuit optimization and structural design of magnetostrictive current sensor are studied.The performance of the sensor is mainly studied from three aspects: material characteristics,magnetic circuit structure and material structure.The specific research work is as follows:(1)Based on the magnetostrictive effect of magnetostrictive materials,the sensing principle and characteristics of magnetostrictive materials are summarized,the preparation process,experimental test platform and experimental equipment needed for magnetostrictive composites are described,and the effects of powder particle size,mass ratio of epoxy resin to powder,mass ratio of epoxy resin to curing agent,oriented magnetic field and strain gauge sticking direction on dynamic and static magnetostrictive coefficients of magnetostrictive composites are studied.(2)The structure and working principle of magnetostrictive current sensor are introduced,and the magnetic circuit of magnetostrictive current sensor is simulated and analyzed by finite element simulation software.According to the magnetic flux density,the magnetic field distribution of magnetostrictive composite material at the gap of magnetic conductor and the influence of the length of gap of magnetic conductor on the performance of sensor are analyzed,and the upper and lower gap lengths of magnetic conductor are optimized.(3)Four kinds of irregular magnetostrictive composite structures are put forward,and the theoretical model of magnetostrictive current sensor is established.At the same time,the size parameters of the four kinds of irregular magnetostrictive composite structures are set and compared with the conventional structure of magnetostrictive composite materials.Finally,the finite element simulation analysis is carried out by COMSOL Multiphysics software,and the performance of magnetostrictive sensors with irregular structure and conventional structure is summarized and compared.(4)The experimental test platform of magnetostrictive current sensor is built,and four kinds of proposed magnetostrictive current sensors are tested and verified,and the characteristics of the four kinds of magnetostrictive current sensors are analyzed.There are 76 figures,6 tables,and 88 references in this thesis. |
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