Self-balancing 20 Hz current comparator

Abstract

The low-frequency transformer is a key measurement equipment for low-frequency transmission engineering; the accuracy level of the low-frequency transformer is generally difficult to be better than 0.05% due to the influence of core depth saturation at low frequency. Explore low-frequency current proportional converters with higher accuracy, such as zero-flux current transformers or compensated current comparators, because the current proportional standards of the above principles all work in the state of zero magnetic flux of the iron core, which is less affected by frequency and can be used to trace the value of low-frequency current proportional value. In view of this, a self-balancing low-frequency current comparator was developed to compensate the excitation current of the iron core by using electronic circuits. In this paper, the basic principle of this low-frequency self-balancing current comparator is expounded, its error performance is analysed theoretically, and the error calibration test is carried out. On the surface of the test results, the accuracy of the low-frequency self-balancing current comparator meets the requirements of class 0.001, which can be used for the traceability of the measurement value of low-frequency current.