| Non-contact current sensing and measurement technique has important application value and potential in insulation detection,power grid monitoring and other fields.The magnetostrictive/piezoelectric laminated magnetoelectric composites has the advantages of simple structure,convenient preparation,and large magnetoelectric conversion coefficient.Existing studies have shown that the lowest detection limit of magnetoelectric composites for magnetic fields can reach the order of p T.Two differential current sensor tags with small size,simple structure and great stability are designed by using FeGa/PZT magnetoelectric composites.The current in wires of different diameters can be measured by using a U-shaped fixture.The differential current sensor tags have been investigated by the means of theoretical analysis,finite element simulation and experiment.The major work is introduced as follows:(1)The basic performance characteristics of FeGa magnetostrictive material and piezoelectric ceramic material are introduced.The magnetoelectric effect and the low frequency magnetoelectric response of the magnetoelectric composites operated in L-T mode are described.The FeGa/PZT magnetoelectric composites were fabricated.The experimental results show that the magnetoelectric element has a flat output in the frequency range of100 k Hz,and the maximum magnetoelectric coefficient is 58 m V/Oe at the bias magnetic field of 170 Oe,and it has the ability to detect low frequency magnetic fields.(2)A type of the differential current sensing tag was designed by dual separable FeGa/PZT magnetoelectric elements.The working principle of the sensor was analyzed and simulated by using Ansoft Maxwell software.The experimental test system of the current sensor was built and the sensor was tested.The experimental results show that the frequency response range of the sensor is from 29Hz(3d B frequency)to 4k Hz or higher,and the flatness is ±0.5d B,and the sensitivity is about 16.2m V/A over the flat response region,and the minimum detection limit achieves 80?A at 1k Hz,and the resolution achieves 50?A at 1k Hz.The differential sensors can effectively suppress the common mode noise,has great antiinterference ability compared with the single magnetoelectric element.(3)Alternative differential current sensor tag was designed by using compact loop magnetic circuit composed of permanent magnet and dual magnetoelectric elements setted close together,which can sense the current sensing by placing it on one side of the current carrying wire.The experimental results show that the sensitivities are 12.7m V/A,13.8m V/A,15 m V/A at the frequencies of 50 Hz,75Hz and 1k Hz in the range of 0-40 A,the minimum detection limit achieves 0.1m A at 1k Hz.The volume of the sensor is smaller and easy to use when compared with the differential current sensing tag with dual separable magnetoelectric elements.Both the differential current sensors can be selected according to the specific application.The gradient measurement method can be used to realize the gradient measurement of the magnetic field around the current-carrying conductor with changing the placement method between the sensing element and the fixture.The current can be calculated by the output of the two magnetoelectric sensing elements,eliminating the measurement error of the position of the wire. |
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