Research On High Frequency Skin Effect Test System For Conductors

When a conductor passes through an alternating current,the cross-sectional current tends to be distributed on the surface due to the effect of electromagnetic induction,resulting in a "skin effect." The existence of the skin effect makes the impedance of the conductor itself increase with the increase of the signal frequency,resulting in a large transmission loss.Researchers at home and abroad have conducted a lot of research on the theory and measurement of skin effect.The existing research methods can be summarized as indirect resistance measurement and direct current measurement.The indirect resistance measurement method mainly uses the equivalent series circuit to measure the change of the internal resistance of the conductor as a whole under the influence of the skin effect.The direct current measurement method is to select the test conductor as a thick conductor,draw out measurement lines at different radius directions of its end faces,and perform direct measurement to analyze the skin effect on the conductor current.This paper first introduces the principle of skin effect,the current density distribution of skin effect and the concept of skin depth.On this basis,a test system that can be compatible with both measurement methods is designed to meet the comprehensive analysis needs of different skin effect measurement methods.The system scheme design was carried out in detail,focusing on high-frequency variable signal source,amplitude stabilization,power amplification,peak detection,test model and system monitoring scheme.Aiming at the hardware circuit design,on the basis of device selection,the schematic design and PCB design of the arbitrary waveform generator based on DDS,peak hold,STM32,communication and power supply are introduced.Aiming at the software design,the STM32 program design based on the time slice rotation scheduling mechanism,the communication program design based on the state machine,the visual upper computer monitoring software design based on Lab VIEW and the upper and lower computer communication protocol design are introduced in detail.Then,based on the design of software and hardware,the system was implemented.The waveforms of key points in the debugging process of the high-frequency DDS signal source circuit,peak detection circuit,and amplifying circuit are introduced in detail.It alsointroduces the debugging method of the software of the upper computer and the software of the lower computer and the problems that occur in the debugging.Finally,using the test system,the skin effect measurement experiments of two measurement methods were carried out,and the measurement results were analyzed in detail.In the meantime,for the "end effect" problem on the outer surface of the conductor in the direct measurement method,a buried hole measurement method was proposed and a detailed measurement model was made.In addition,in order to explore the current density distribution on the cross section of the conductor,the skin effect in the conductor at high frequency is simulated based on the ANSYS Maxwell finite element simulation software,and detailed simulation analysis results are given.Experiments show that the test system works normally and the software and hardware are reliable.With the two measurement methods,the measurement and analysis of the skin effect of the conductor at different frequencies are achieved and the expected goal is achieved.