摘要
磁屏蔽磁场的分析是实现高精度电流比较仪优化设计的关键,然而磁屏蔽气隙结构复杂,有限元法计算量大、计算精度难以满足要求。考虑磁屏蔽分层结构以及一次电流偏心和外部磁场干扰对磁场分布的影响,提出一个二维简化模型,利用极坐标系下Poisson方程解的正交函数展开式推导磁场的解析解,并利用有限元法验证解析解的正确性。通过二维解析模型与三维实际问题有限元计算结果的对比,发现两者具有简单的比例关系,且该比例关系不依赖于干扰源的位置,因此可用二维解析模型对三维实际磁屏蔽结构做出快速有效的评估。对坡莫合金的B-H曲线进行拟合,以线性近似下的磁场解析解为基础,利用安匝平衡时检测线圈的感应电压导出电流检测的误差估算公式,作为磁屏蔽效能分析的定量指标。对不同磁屏蔽结构的分析表明,双层结构比同样尺寸单层结构的屏蔽效能可提高近三个数量级。最后通过实验验证了解析表达式分析实际问题的有效性。
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 2 D 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 2 D analytic prediction is found proportional to the 3 D FEA result for a practical problem,and the proportion is not dependent on the location of the interference source. This good feature makes the 2 D 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.
出处
《电工技术学报》
EI
CSCD
北大核心
2017年第21期73-80,共8页
Transactions of China Electrotechnical Society
基金
国家电网公司纵向科技项目(JL-71-15-048)
湖北省非动力核技术协同创新中心资助
关键词
电流比较仪
磁屏蔽
磁场分析
解析解
屏蔽效能
误差评估
Current comparators
magnetic shielding
magnetic field analysis
analytical solution
magnetic shielding effectiveness
error estimation
