Research On Current Sensing Technology And Device System Using Resonant Magnetic Sensor

Current sensing technology plays a very important role in the field of online monitoring,relay protection,power maintenance and intelligent equipment control in power system.With the expansion of power grid scale and concept of electronic equipment health monitoring,it is urgent to provide information support for its control decision through advanced sensing and measurement technology.In this paper,a resonant magnetic sensor based on the composite structure of magnetostrictive material and tuning fork resonator is used to design a resonant current sensor,which has the advantages of small volume,low power consumption and high sensitivity,and can be used for dc and ac current measurement.The resonant current sensor is studied through theoretical analysis,finite element simulation and experimental test.Its main work is as follows:The principle and composition of resonant magnetic sensor are introduced.The preparation of magnetic sensitive cell is described and the performance of the sensor is tested.The paper also introduces the design of the sensor detection circuit.Circuit simulation is combined with formula derivation to analyse its working principle.The commonly used frequency signal detection methods are introduced and the performance of the frequency measurement chip is tested.What's more,working principle of current measurement with single unit resonant magnetic sensor is analysed.We prepared the sensors and set up the experimental system to measure the sensitivity and resolution of the sensor.The result shows that 0-10 A dc measurement sensitivity and resolution are 0.9 Hz/A and 0.1 A,0-70 A ac measurement sensitivity and resolution are 0.704 Hz/A and 1 A.we also tested the temperature characteristics of the sensor and its performance is greatly affected by temperature.On this basis,the differential resonant current sensor is designed for non-access and access current measurement schemes.A mathematical model of the output frequency and input current of the sensor is established through formula derivation for the two current measurement schemes.Based on the finite element simulation,the working principle of current measurement is analyzed.The differential resonant current sensor is prepared,and the experimental system was built to test the performance of the sensor.For 0-10 A dc measurement,the sensitivity and resolution of the single conductor are 1.36Hz/A and 30 m A respectively.The measurement sensitivity and resolution of the spiral coil are25.2Hz/A and 5m A.During the ac measurement,the sensitivity and the resolution of the nonaccess type is 1.05Hz/A(0-70A)and 1A.The sensitivity and the resolution of access type measurement is 13.7Hz/A(0-20A)and 0.1A.The result of temperature experiment shows that the nonlinear temperature coefficient of differential sensor is one order of magnitude smaller than that of single sensor,and the temperature drift is effectively inhibited.For dynamic signal measurement,the current measurement is studied by using the fast response characteristic of F/V conversion circuit.The working principle of F-V converter circuit is analyzed.An experimental testing system was built to test the ac/dc characteristics of the differential resonant current sensor.The results showed that the sensitivity of the dc sensor is2.81 m V/A in the range of 0-10 A and 1.7m V/A in the range of 0-200 A.During the ac measurement,the sensitivity in the 0-70 A range was 0.0934 m V/A,and in the 0-150 A range was0.0493 m V/A.