Single Magnetic Ring Dual-range TMR Current Sensor Based On Magnetic Shunt And Magnetic Aggregation Structure

With the continuous promotion of the "carbon peak" and "carbon neutral" national strategic objectives,China’s green industries such as electrical vehicles,photovoltaic power generation and smart grid have made great progress.In application scenarios such as electrical vehicle charging pile,power transmission and transformation system,it may be necessary to measure large current signal and small current signal simultaneously.It is impossible for a single-range current sensor to meet the performance requirements of large-range and high resolution at the same time.Therefore,the research of dual-range current sensor is necessary and has important research significance and practical value.The research goal of this thesis is to design a single magnetic ring dual-range TMR current sensor.Firstly,based on the research of current sensors reported in domestic and foreign relevant literature,several main current sensor technologies are compared and analyzed from the aspects of measurement principle and technical characteristics,among which the tunnel junction magnetoresistance sensor has the advantages of wide linear range,high resolution and high sensitivity,which is suitable for the design of a single magnetic ring dual range current sensor.A new design method of dual-range current sensor based on single magnetic ring is proposed.The dual-range current sensor is designed by analyzing and utilizing two different magnetic guiding effects,magnetic shunt and magnetic aggregation,generated at different positions in the single magnetic ring.The design method of double-range current sensor with single magnetic loop is explained theoretically by combining the magnetic shunt/magnetic aggregation technique with the closed-loop feedback technique,and the mathematical model of the system is established and the magnetic circuit of the magnetic loop structure is analyzed.The magnetic ring structure and the feedback coils are simulated and designed respectively,and the design parameters such as the size of the magnetic ring and the number of turns of the coil are optimized.With the guidance of electromagnetic simulation and theoretical calculation,the suitable positions of the two TMR sensor chips for different current ranges are designed.In terms of hardware design,the weak signal output by the sensor chip is amplified to form closed-loop feedback,and after analog-to-digital conversion,the main control chip is used for automatic acquisition and serial signal output.In addition,the main control chip is used to control the relay switch to achieve automatic switching between the two current ranges.The two detection probes for different current ranges share the same set of magnetic ring,feedback coil and signal processing circuit to save costs and reduce power consumption.A dual range current sensor with large range,high linearity and high accuracy and automatic range switching is realized.The function modules of data acquisition,digital filtering and range switching are programmed in the software design to realize a dual range current sensor with large range,high linearity and high accuracy,and automatic switching function.Aiming at the problem that the traditional single air gap current sensor cannot be opened and closed,the magnetic ring designed in this system is a double air gap structure,and the system assembly shell is designed to realize a current sensor that can be opened and closed during the measurement process without damaging the circuit being measured.Finally,based on the system test platform and scientific test and evaluation method,the main performance characteristics of the dual-range current sensor are measured and evaluated.The test results demonstrate that the large range current sensor shows good performances: a linear measurement range of 0 ～ ±1000 A,the small range current sensor also exhibits excellent performances: a linear range of 0 ～ ±10 A,a high resolution of 500 μA.The overall linearity of the system is lower than 0.03%,the repeatability is 0.06%,the accuracy is 0.09%,and the working bandwidth is higher than 500 k Hz.Compared with other reported research results and similar commercial current sensors,several key performance parameters of this work are better.The current sensor designed in this work benefits many advantages such as wide range,high resolution and high linearity,and can be potentially applied in areas of electrical vehicles,clean energy industry and other electrical related fields.