Kaczmarek Michał
Institute of Mechatronics and Information Systems, Lodz University of Technology, Łódź, Poland.
Sci Rep. 2025 Mar 23;15(1):10011. doi: 10.1038/s41598-025-94803-7.
This paper explores the implications of employing a load exhibiting a power factor of 1 to test the transformation accuracy of an inductive current transformer with an apparent power below 5 VA. It offers an explanation of the change in current error and phase displacement correlates with the load power factor. The impact of the load power factor on the secondary winding on the accuracy of inductive CT is investigated in detail. The paper introduces a newly developed method that allows for the calculation of current error and phase displacement values for any power factor with consideration of the nonlinearity of the magnetization characteristic of the magnetic core. To ensure required accuracy of calculations of utmost significance is the potential RMS value modification of the magnetic core excitation voltage, which may further impact the transformation accuracy. Consequently, the operational conditions during the test are modified, and, owing to the nonlinearity of the magnetization characteristic of the magnetic core, the values of current error and phase displacement are also changed-not only due to a different load power factor connected to the secondary winding of the tested inductive current transformer. To maintain consistent operational conditions for a given secondary winding load power factor, the resistance connected to the secondary winding during the accuracy test with the power factor equal to 1 should be corrected. Moreover, the findings of this paper lead to the conclusion that evaluation of the transformation accuracy of inductive current transformer for both secondary winding load power factors is essential to ensure its reliable future operation in real conditions with the required accuracy class.
本文探讨了采用功率因数为1的负载来测试视在功率低于5VA的感应式电流互感器的变比精度的影响。文中解释了电流误差和相位移的变化与负载功率因数的关系。详细研究了负载功率因数对感应式电流互感器二次绕组精度的影响。本文介绍了一种新开发的方法，该方法考虑了磁芯磁化特性的非线性，能够计算任意功率因数下的电流误差和相位移值。为确保计算的准确性至关重要的是磁芯励磁电压的有效值可能会进一步影响变比精度。因此，测试期间的运行条件会发生变化，并且由于磁芯磁化特性的非线性，电流误差和相位移的值也会改变，这不仅是因为连接到被测感应式电流互感器二次绕组的负载功率因数不同。为了在给定的二次绕组负载功率因数下保持一致的运行条件，在功率因数等于1的精度测试期间连接到二次绕组的电阻应进行校正。此外，本文的研究结果得出结论，评估感应式电流互感器在两种二次绕组负载功率因数下的变比精度对于确保其在实际条件下以所需精度等级可靠运行至关重要。
