| With the development of social economy,the use of power cables is increasing.At the same time,due to the influence of natural factors and human factors,the cable is prone to failure.In order to ensure the stable operation of cable,the detection of cable is very important to the reliability of power supply.Although the traditional sensor based on electric field can detect cable aging,defects and faults,the operation process is complex,and the efficiency of detection needs to be further improved.Therefore,based on the electromagnetic characteristics of power cable,this paper proposes the design and research of a magnetic field sensor for fast detection of power cable.In this paper,the magnetic field around the cable was calculated by simulation,and Faraday’s law of electromagnetic induction was selected as the basic principle of the sensor.The designed magnetic field sensor is mainly composed of three parts: magnetic core,coil and amplifier circuit.The influence of each part on the performance of the sensor was studied in detail,and each part was optimized.The sensitivity calibration and actual detection of the designed magnetic field sensor were carried out.Various core materials were compared and analyzed from the perspectives of magnetization curve,hysteresis loss,eddy current loss and residual loss.Based on the model of magnetic field sensor established by COMSOL,the effect of the length of magnetic core,the ratio of length to diameter of magnetic core,the ratio of coil length to core length,and the performance of flux collector on magnetic field sensor were analyzed.The results show that permalloy is the most suitable material for magnetic core in magnetic field sensor.The optimum ratio of length to diameter is 20,and the ratio of coil length to core length is 0.3.When the length of the core is small or the length of the core is smaller,the efficiency of adding flux collector to increase the effective permeability of the core is not high;When the core length reaches a certain value,the efficiency of adding flux collector is higher.Based on the coil simulation model established by COMSOL,the influencing factors of coil resistance and inductance were analyzed.The fitting formulas of coil resistance and inductance were obtained and verified by experiments.Considering the coil quality and noise of magnetic field sensor,the coil turns and the diameter of copper enameled wire were optimized.The results show that the coil turns,coil length,diameter of copper enameled wire and coil radius will affect the resistance and inductance of the coil.The optimal number of coil turns is 11000 turns,and the optimal diameter of enameled copper wire is 0.08 mm.An amplifying circuit based on flux negative feedback was designed.The performance analysis was carried out in Multisim.The PCB of the amplifier circuit was designed by using Altium designer 20,and the actual effect of the amplifier circuit was measured by welding the circuit.The results show that the negative flux feedback expands the frequency band of the sensor,improves the amplitude frequency characteristics and phase frequency characteristics of the amplification circuit,and meets the design requirements.The designed magnetic field sensor was assembled.An experimental circuit was built to calibrate the sensitivity of the magnetic field sensor,and the actual measurement was carried out.The results show that the developed magnetic field sensor has a sensitivity of 327.6 m V/μT,small size,high sensitivity,convenient carrying and high reliability. |
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