The Development and Performance of Dual-Core DC Tolerant Current Transformer

A current transformer (CT), consisting of two independent magnetic cores, is proposed to improve the DC tolerance ability for AC measurement. The proposed dual-core CT is designed to work at the low measurement error margins of the conventional and air-gapped CTs, which exhibits a high accuracy for AC measurement of the conventional CT and, in the meanwhile, as tolerant to DC saturation as the air-gapped CT. An analytical model for magnetostatic evaluation that fits both conventional and air-gapped CTs is presented, and the measurement error of the dual-core CT is determined accordingly. A prototype of the dual-core CT is constructed and the performance of two kinds of cores for current measurement under different DC biases is experimentally evaluated. Comparisons between error calculation and error measurement of the dual-core CT are also conducted. The experiment result verifies the theoretical prediction of the dual-core CT, showing the proposal of an interesting AC measurement solution in industrial applications.