Analytical Solution of Magnetic Field for Current Comparator's Multilayer Shield with Tiny Air Gap
Zheng Tianyu 1, Chen Dezhi1, Wang Xue 2, Hu Haoliang2, Li Dong1
1.State Key Laboratory of Advanced Electromagnetic Engineering and Technology Huazhong University of Science and Technology Wuhan 430074 China 2.China Electric Power Research Institute Wuhan 430074 China
Abstract：The analysis of the magnetic field is very important for the design of a current comparator(CT).However,for its complex air-gap structure,it is difficult to obtain a desired simulation accuracy by using finite element analysis(FEA)with acceptable calculations.In this paper,a simplified 2D model for CT is proposed,and an analytic solution,taking into account the interference of both the eccentric primary current and the external magnetic field,is derived for multilayered magnetic shield.Using the orthogonal function expansion of the Poisson equation,the analytic solution is derived and it is verified by the FEA result.The 2D analytic prediction is found proportional to the 3D FEA result for a practical problem,and the proportion is not dependent on the location of the interference source.This good feature makes the 2D analytic model a quick and effective tool to evaluate an actual magnetic shield.Based on the fitted B-H curve for the perm alloy and the linear approximation analysis of magnetic field,a formula is derived from the induced voltage of the test coil when Ampere-turns are balanced which is used for a quantitative index for the magnetic shield's effectiveness.The analyze of magnetic shield with different structure indicates that the double-layer shield's effectiveness is nearly three order of magnitudes better than the single-layer shield's.Finally an experiment was carried out to verify the analytical results.
郑天宇, 陈德智, 王雪, 胡浩亮, 李冬. 电流比较仪多层小气隙磁屏蔽磁场的解析解[J]. 电工技术学报, 2017, 32(21): 153-160.
Zheng Tianyu, Chen Dezhi, Wang Xue, Hu Haoliang, Li Dong. Analytical Solution of Magnetic Field for Current Comparator's Multilayer Shield with Tiny Air Gap. Transactions of China Electrotechnical Society, 2017, 32(21): 153-160.
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2017, Vol. 32 
