Study On 3D Coreless Current Transducer Based On Tunnel Magnetoresistance

With the popularization of electric vehicles,more and more charging piles appear in the city,the monitoring of the operation of charging piles includes both AC current and DC current,and due to the wiring in the charging pile is in a small space,it is necessary to design a miniaturized,AC/DC measurement,frequency bandwidth,easy installing and low-cost current transducer.The iron-free current transducer has been widely used in current measurement because of its advantages of small size,large dynamic range,high sensitivity,frequency bandwidth and low cost.It can not only measure the AC/DC current at the same time,but also ignore iron core.Combined with the printed circuit board process,the iron-free current transducer is easy to use and replacing the magnetic sensor elements can meet the accuracy of different current measurement occasions.However,in recent years,coreless current transducer’s research is based on the central axis of the wire to be perpendicular to the magnetic sensor array plane,and the actual measurement occasions can not meet the strict vertical relationship.The measurement error caused by the wire is not vertical with the magnetic sensor array plane has not been eliminated until now.Therefore,in order to realizing miniaturization and AC/DC measurement,this paper mainly studies the accurate measurement of the current when the wire is inclined and eccentric,and solves it by means of correction algorithm.In this paper,a three-dimensional tunnel magnetoresistance(TMR)sensor array scheme and a 3D TMR sensor array current measurement method for eccentric and inclined current correction calculation are presented,and then the principle,formula derivation and simulation process of 3D TMR sensor array current measurement method are described in detail,and the performance of the algorithm is analyzed comprehensively.The comparison of influence of inclined angle on the measurement error between the Ampere’s law algorithm,the two-dimensional sensor array current algorithm,and the 3D TMR sensor array current measurement method is carried out in this paper,and simulation results show that the 3D TMR sensor array current measurement method greatly improves the measurement accuracy of the current when conductor is eccentric and inclined.Based on the three-dimensional TMR element’s high sensitivity and stability,this paper designs a ring-shaped,small-size coreless TMR current transducer,which can obtain the distribution of magnetic flux density in the x,y,z direction when the conductor is inclined.With the designed coreless TMR current transducer,the actual measurement effect of Ampere’s law algorithm,two-dimensional sensor array current algorithm and 3D TMR sensor array current measurement method is compared under DC and AC.Then the current calculation effect of 3D TMR sensor array current measurement method on different inclined and eccentric positions is verified under DC and AC.The experimental results show that the DC measurement error of 3D TMR sensor array current measurement method is 1.984%,and the AC measurement error is 2.086%,realizing the accurate measurement of the current when the conductor is eccentric and inclined.