电流比较仪式电桥自动平衡算法设计与测试

摘要

This paper designs an automatic balancing algorithm of current comparator bridge to get dielectric loss tanδ and capacitance. In order to eliminate unbalanced state between test capacitor arm and standard capacitor arm, the algorithm outputs the parameter (N2 turns & gain β) to make output voltage tend to zero by measuring the null detector output voltage and current of standard capacitor bridge arm. And it also uses Newton-Raphson iteration method to get more accurate parameter and then calculate tanδand capacitance value. This paper tests the capability of the algorithm in a condition of the power with stable frequency, changing frequency and AC power waveform mixed harmonics. The result shows that this algorithm has high precision and good stability.%　　设计了电流比较仪式电桥的自动平衡算法，可测量电容器介质损耗角正切值及电容值。本算法是为了矫正试品电容器与标准电容器桥臂间的不平衡状态，通过测量标准电容器桥臂电流和检零计输出电压，输出匝数N2和增益β两个平衡参数，使检零计输出趋零。算法基于牛顿拉夫逊迭代方法，可由输出电压值修正得到精度更高的平衡参数，并用电桥平衡后的参数计算出正切值及电容值。本文测试了在电源频率偏差、频率波动、电源波形参杂谐波等多种条件下的性能，表明该算法精度高，稳定性好。