Modeling And Analysis Of The Breakdown Characteristics Of Protective Devices Under Different Time-scale Disturbance

Electronic system equipment ports are often interfered by external transient overvoltages.These interferences mainly include micro-second(μs)level surge electromagnetic pulses and nano-second(ns)level electrostatic discharge electromagnetic pulses,which will cause fatal damage electronic equipment and device,Therefore the research of electromagnetic pulse and electromagnetic pulse protection devices is particularly important.Based on the current research status,firstly developiing a printed circuit board(PCB)test combination wave generator controlled by mercury switch to generate microsecond-level surge electromagnetic pulses;A nanosecond-level electrostatic discharge experiment platform is built,and the circuit model under the 50Ω test system is established for used the 3Ctest brand electrostatic gun,and then the accuracy of the built model is verified by comparison with the actual test results.Secondly,based on the actual test,the volt-ampere characteristic curve of the metal oxide varistors(MOV)of the voltage-limiting protective device is obtained and fitted,and the varistor diode circuit model and the nonlinear device circuit model are established in the circuit simulation software,the physical structure model of the varistor is established by using the nonlinear conductivity characteristics of the varistor in the Quickfield 3D electromagnetic field modeling tool.The surge immunity test is performed on the varistor,and the simulation results of the built model are compared to verify the accuracy of the built model.The response of different types of varistors to electrostatic discharge is compared and the relationship between the capacitance of different devices and the response voltage waveform is found.Next,for the gas spark gap device,a schematic diagram of its response characteristics under electrostatic discharge is proposed.Then,five different types of gas discharge tubes(GDT)are selected,and four different tip structure PCB spark gaps are fabricated for electrostatic discharge impact test.The influence of device parameters and structure on the random range of breakdown delay under different voltage levels is discussed,and the relationship curve and formula of the delay and electrostatic discharge voltage level are given;it is also proposed to add carbon to the negative electrode for the PCB spark gap to improve the launch ability of the electron,thereby improving the breakdown stability.Finally,based on the test and analysis of response characteristics of the gas spark gap device,a circuit model of the gap device under electrostatic discharge is proposed.Three typical arc resistance models: Toepler model,Rompe-Weizel model,and Vlastos model are introduced.The derivation process of the model formula is summarized,and the circuit is realized in the simulation software;combined with the circuit description of the breakdown time delay of the device,the simul ation model of the spark gap device is established,and the accuracy of the model is verified,which provides an effective simulation calculation method for its circuit design and practical application.The innovations in this dissertation are summarized as follows:(1)Based on the double exponential function,a PCB board-level test surge combined wave generator controlled by a mercury switch is designed and implemented.(2)It is difficult to model the nonlinear conductivity of materials in the time domain electromagnetic numerical calculation.In this paper,a three-dimensional electromagnetic model of MOV is established in Quick File tool.The nonlinear conductivity of MOV materials is imported and compared with the simulation results of diode circuit model and nonlinear device circuit model under t he impact of surge.(3)The random range of the time delay of different types of gas discharge tubes and PCB spark gap devices with different gap structures under different electrostatic discharge voltage levels is studied,and the relationship between the time delay and the discharge voltage level is given.The circuit equivalent form of the time-varying arc resistance is proposed,and the circuit simulation model of the gas gap device is established based on the time delay characteristics.