Research And Application On Current Sensors Based On Magnetoelectric Laminate Composites

In the context of “Ubiquitous power Internet of things”,a large number of optimizations are needed in terms of status evaluation,fault location and scheduling on power grid.Under the new situation,considering the limitations of existing current measurement technologies,a new non-invasive self-powered wireless current sensing technology is urgently needed to obtain current information of the power grid and monitor its status,so as to ensure safe operation of the power grid.Magnetoelectric laminate composites with advantages of passive,simple structure and high magnetoelectric coefficient at room temperature are ideal transducers for new current sensors.Although the previous researches have improved performances of the magnetoelectric sensors by optimizing the materials,structures and external constraints,there are still some problems in the existing magnetoelectric current sensors,such as low sensitivity,dependence on bias magnetic field,non-adjustable resonance frequency and bias magnetic field.Hence,this paper presents a self-biased weak-current sensor and a bias-tunable weak-current sensor.And,their performances were analyzed by theoretical and experimental meth-ods.Finally,based on the simulation results of different magnetic cores,a magnetoelectric heavy-current sensor was developed.And,a wireless current measurement system was built,the magnetoelectric heavy-current sensor was applied in practice.The main results and con-clusions are as follows:1.A self-biased magnetoelectric weak-current sensor based on SrFe₁₂O₁₉/FeCuNbSiB/PZT was presented.The SrFe₁₂O₁₉ribbon with a large coercive field provides a huge internal magnetic field to bias the magnetostrictive FeCuNbSiB layers,which can increase the magnetic moment reorientation of FeCuNbSiB layers.Consequently,it can enhance the sensitivity of the sensor.Experimental results demonstrate that the presented sensor has a higher sensitivity of?198.91 m V/A and a good linearity to the applied 50 Hz current.Also,the sensor can distinguish small step changes of?0.01 A current.2.A weak-current sensor based on FeCuNbSiB/PZT magnetoelectric composite with a bias-tunable magnetic concentrator was presented.The concentrator can enable the DC bias magnetic field to become tunable to meet the needed optimal value of FeCuNbSiB/PZT and to reduce the magnetoresistance of the magnetic loop,which can enhance the sensitivity.Further-more,the sensor's resonant frequency is adjustable to improve the sensitivity for measuring current at different frequencies.From experiments,the proposed sensor has a sensitivity of?246.71 m V/A and a linearity of?0.98%(R²=0.9969)at 50 Hz current.3.Based on simulation results of COMSOL^?and Terfenol-D/PZT/Terfenol-D magne-toelectric composite,a magnetoelectric heavy-current sensor was fabricated.Compared with conventional electromagnetic transformers,it has a wider measurement range(50–1000 A)and a smaller measurement angle difference.And,it was applied in the wireless current measure-ment system with self-powered function.According to the test,the measurement error of the system is not greater than±1%under a current range of 100–600 A,and the sampling rate is up to one second.