Research On Arc Discharge Time And Evaluation Method Of Inductive Intrinsically Safe Circuits

At present,the test of intrinsic safety performance of electrical equipment applied to explosive gas environment needs to be tested on explosive test of IEC spark test device.In order to improve the sensitivity,reliability and stability of explosive test,it is an effective way to improve the IEC spark test device and improve the test method.Because of the shortcomings of the explosive evaluation method,the research on the non explosion evaluation method is not yet comprehensive.Therefore,it is necessary to carry out the research on the non explosion evaluation method.In view of the above situation,the following research work has been done.By considering the two-electrode tungsten wire and cadmium disk of the IEC spark tester as ideal cylinders,the actual separation speed of the electrode was taken into account,and the capacitance between the two electrodes was expressed as a function of time,and the dynamic volt-ampere characteristic model of the arc discharge was used.Finally,the entire process simulation of inductive circuit arc discharge was realized.During the explosive detection test,it was found that the spark discharge time showed a double normal distribution.By calculating the actual firing interval of the tungsten wire,taking into account the actual separation speed of the tungsten wire,the minimum and maximum discharge time determined by the mechanical characteristics were obtained,and the double normality was explained,and its existence criteria was established.For many limitations of the existing power criterion,based on the theory of thermal ignition,the discharge time factor was took into account,and the model of the constant heat source heat source temperature field was used,and whether the time when the temperature of the initial combustion volume is lowered from the highest value to the combustion temperature of the gas mixture is greater than the time of the chemical reaction was regarded as a critical condition for judging whether the spark can successfully ignite the gas mixture.Then,the corresponding spark discharge time threshold was obtained,and it is corrected based on the minimum ignition current curve.At last,the discharge time discriminant and average power discriminant for evaluating the intrinsic safety performance of inductive circuits was established.The verification results showed that the discriminant obtained can be used to judge the intrinsic safety performance of the circuit,and the discriminatory results are conservative.Based on the open-circuit arc discharge characteristics of the switching converter and its energy transmission process,the discharge time discriminant for evaluation of the intrinsic safety performance of the switching converter was established by obtaining the arc discharge time and discharge energy.In addition,a circuit intrinsically safe performance evaluation software was developed using VS2015.The software functions include the simple circuit(inductive circuit,capacitor circuit and load circuit with resistive shunt)and the intrinsic safety performance evaluation of the switching converter circuit and intrinsically safe switching converter parameter design guidance.