A new bifilar ac resistor with calculable frequency dependency is developed to establish the ac resistance standard at NIM. A 2-dimensional model is provided to get the equation to describe the electromagnetic field and to calculate the ac/dc difference of the resister. Its outstanding features over other published ones, such as coaxial, quadrifilar and octofilar types, are its very small ac/dc difference and better stability resisting the mechanical shock. In addition, with the design it is possible to use thicker and longer wire to reduce the self-heating of the resistor carrying current, and thus the fine adjustment of the resistance value becomes easier.%提出了一种新型交直流差可计算电阻方案,并建立了数学模型,推导出此种结构的电磁场计算公式,进而计算出此种新型电阻在0～100 kHz内的交直流差.与"同轴线型"、"四回线型"和"八回线型"等方案相比,该结构具有较小的交直流差和较好的机械稳定性.此外,文中提出的结构更为紧凑,因而可使用线径较粗的电阻丝,电阻的自发热问题不明显,不需要使用浸入硅油等散热措施,电阻值的细微调整也比较容易.
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