A High Accuracy AC+DC Current Transducer for Calibration

Abstract

Facing a lack of high accuracy current standards in the calibration of AC (Alternating Current) + DC (Direct Current) measurement devices that function to measure DC and AC simultaneously, a measurement method with high accuracy is proposed based on zero-flux self-oscillating fluxgate. An iron core and two windings are added onto the single-iron-core double-winding structure of the traditional self-oscillating fluxgate. The added iron core and its upper winding are used to weaken the influence of ripple on the sensor’s accuracy. The other one of the added windings is used for the feedback from the AC+DC magnetic potential, allowing the sensor to work in a zero-flux state and to measure AC+DC simultaneously. An AC+DC transducer prototype with an AC ranging from 0–500 A and DC 0–300 A is developed by selecting the core parameters and an optimized design of the circuit. The test results of the prototype show that the prototype can measure the AC and DC simultaneously, and the measurement accuracy reaches class 0.05 level in the nominal current range. This transducer can be used as a calibration standard of measurement devices for AC only, DC only, or AC and DC simultaneously. Compared with the AC+DC current transducer with the same accuracy level, the proposed transducer has fewer cores and simpler measuring circuit.

Online Measurement Method and System of Excitation Impedance of Current Transformers Based on Norton’s Theorem and Differential Method to Measure Difference of Two Currents

“…Its basic principle is to compare the measured CT with a standard CT with a higher accuracy class to determine the ratio error and phase displacement. Numerous studies have been devoted to improving the measurement range and accuracy of the comparison method [2][3][4][5].…”

Operation of the Electronic Current Transformer for Transformation of Distorted Current Higher Harmonics

“…Moreover, to characterize the transducers under real operating conditions, additional tests were performed using developed synthetic complex waveforms. The most popular technology used in ECTs is based on Hall effect sensors [9,10]. In [11], the authors described a method to test the accuracy of ECTs equipped with both analog and digital outputs.…”

An adaptive error compensation method for wide-range current transformers based on segmentation and dimensionality reduction

“…The errors in current transformers are mainly caused by the excitation current required to build up the flux in the core. The non-linear nature of the excitation current makes it difficult to reduce it in order to improve the accuracy of the current transformer [1][2][3]. The current error in uncompensated current transformers is mostly negative, and appropriate compensation methods can reduce the ratio difference and phase difference.…”