Study On Residual Energy Of Fieldbus Intrinsic Safety System

The existing intrinsic safety system of fieldbus in dangerous places only considers cutting off the power after the fault occurs and reducing the source of arc energy.However,the residual energy in the energy storage element may also affect the intrinsic safety,so it is necessary to carry out theoretical and experimental research on the calculation and influence of residual energy.Because of the huge amount of switching power supply applied in the field bus intrinsic safety system,it directly affects the Intrinsic Safety of the system,and the switching converter is the main component of switching power supply,therefore,the residual energy of Buck,Boost and Buck-Boost converters should be analyzed theoretically and verified by simulation,considering both the cable length and the load characteristics.Firstly,the residual energy of Buck converter in DCM and CCM operating modes is analyzed,and the relationship between the maximum residual energy and the parameters in the circuit is obtained,secondly,the residual energy formula of Boost and buck-Boost circuits in CCM mode is analyzed,and the relationship between the maximum residual energy and the parameters is obtained.The improvement and comparison of the formulas for calculating the residual energy of three kinds of switching converters provide some theoretical support for the analysis of circuit safety and the design of Intrinsic Safety Circuit.Then,the relationship between the residual energy and the cable length after the failure of the three switch converters is calculated and analyzed respectively,and the cable position corresponding to the maximum residual energy can be obtained,so as to take preventive measures in advance,quickly cut off the fault,and better ensure the intrinsic safety performance of the field bus system.The formula of"L₀/R₀"connecting three kinds of switching converters in IEC60079-11 standard is updated,which can better guarantee the essential safety of the system.Finally,the experiment is carried out when the Buck converter is connected to four cables of different lengths under the CCM operation mode.Through simulation and test verification,it is found that there is a maximum value of residual energy under certain conditions.Secondly,the simulation and test of Buck power supply in connection with resistive load and inductive load are carried out.It is found that the variation law of residual energy with the cable length is different when the load with different properties is connected.Through the research and analysis of three kinds of switching converters and the residual energy after the load is connected by cable,the relationship between the residual energy and the circuit parameters and the cable length is found in this paper,which provides a theoretical basis for improving the intrinsic safety of the field bus.