Introduction to the functional principle of split core current transformer

The split core current transformer has a unique advantage in terms of ease of use, especially in field measurement occasions where interruption is not allowed. It is almost a fixed choice. The split core current transformer on the market are mainly based on the Hall principle or Rogowski coil. Due to the working principle, the accuracy is generally not high, and can only achieve about 1%. In fields such as power measurement, a large number of products with an accuracy level of 0.1% or higher are required, but the current products cannot meet the performance requirements.At present, the full-scale accuracy of our SCI series of split core transformer is 0.1% and 0.02%, and the range covers 100A to 5000A. The measurement frequency range is from DC to hundreds of kHz. High-precision split core current transformer.

II. Design principle of split core current transformer

Traditional split core current transformer, whether based on the Hall principle or Rogowski coil, theoretically cannot achieve high accuracy. Sensors based on the Hall principle, even the non-open-loop closed-loop Hall sensors with high accuracy, have an upper limit of only about 0.3%. If they are made into open-loop ones, the accuracy will be further reduced. The disadvantage of Rogowski coils is also low accuracy. Flexible Rogowski coils can only achieve 1%. There are other obvious disadvantages, such as inability to measure DC, poor low-frequency characteristics, poor waveform quality, and obvious phase delay.

High-precision split core current sensors, which belong to a type of direct coupled current transformer (DCCT), are a new generation of isolated current measurement devices that can measure DC, AC or pulse currents and have high-level test accuracy. In addition to the advantages of isolated measurement, it also has a series of significant advantages such as wide measurement dynamic range, extremely high measurement accuracy, wide bandwidth, fast response speed, and basically not affected by external environment such as temperature. Compared with the previous generation of Hall resistance current sensors, its performance has been qualitatively improved.

The basic principle of our SCI series sensors is based on the new magnetic modulation zero flux technology. By driving the feedback current to compensate for the influence of the bus current on the magnetic ring, the zero flux state in the magnetic ring is measured, and the nearly ideal bus current-output current ratio is achieved.

The SCI series of high-precision split core current sensors apply the zero flux principle. Through the superior modulation and demodulation design ideas, the high performance of this series of sensors is guaranteed in principle; through efficient self-recovery logic, high reliability under complex working conditions is achieved; through the optimization of process manufacturing and processing flow, excellent product performance and ease of use are achieved.

III. High-precision open-close current sensor index test

For the performance test of the SCI series of high-precision open-close current sensors, our company selected high-precision current sensors calibrated by the China Institute of Metrology and awarded with calibration certificates for comparison test. However, due to the poor intuitiveness of the comparison method, our company uses the source meter method to test it on the basis of ensuring the accuracy of the open-close current sensor, so that customers can see it at a glance.

We selected the high-precision split core current sensor SCI-600 with a range of 600A and a full-scale accuracy of 0.02% for testing. As shown in Figures 3 and 4, we selected the SCS-1500AU DC large current source with a full range of 1500A and an accuracy of 0.01% independently developed by our company as the test DC current source, the eight-and-a-half-digit meter as the test meter, and the voltage range (here we selected the Vishay series resistor with a calibrated resistance of 1.000006Ω as the load resistor for testing).

IV. Advantages

The SCI series split core current sensor adopts an open-close through-core structure, provides a variety of measurement apertures and ranges to choose from, and does not need to disconnect the busbar to be measured, which is convenient for installation and measurement. It is mainly used in the field of DC, AC and pulse current measurement that requires high measurement accuracy. The primary and secondary currents are isolated from each other, and the safety performance is excellent.

Performance characteristics:

Open-and-close type, easy to install and measure

Advanced zero-flux closed-loop current sensor

Excellent linearity and accuracy

Extremely low temperature drift

Wide bandwidth and low response time

Isolated measurement of primary and secondary sides

Strong anti-interference ability