Research On Explosion Protection Functional Safety Of Variable Frequency Drive System In Explosive Atmospheres

In modern industrial explosive atmosphere such as coal mines and petrochemicals,variable frequency drive systems are widely used as the power source of the production process.The explosion risk increases and higher requirements are placed on explosion protection safety.Aiming at the high reliability and high safety level of the variable frequency drive system in explosive atmosphere,this dissertation takes the functional safety theory as the background,combined with the standards of electrical explosion protection,and takes the realization of explosion protection functional safety and the improvement of the safety level as the guideline.More research was carried out on the functional safety assessment of the system's explosion protection function.The main achievements of this dissertation are as follows:(1)An evaluation method for the protection level of explosion protection equipment based on improved functional safety is proposedBy analyzing the potential ignition source of the explosion protection variable frequency drive system and the corresponding explosion protection measures,the functional safety assessment method that is only applicable to electronic/electrical/programmable controller(E/E/PE)safety devices has been improved,and the definition of safety devices has been expanded comprehensive electromechanical measures such as traditional explosion protection types.Taking a typical explosion protection variable frequency drive system as an example,the failure mode and effect analysis(FMEA)method is used to analyze its safety devices to obtain the failure rate and safety failure score,and to determine the system safety integrity level(SIL)and equipment protection level(EPL).Finally,a mathematical method was used to compare the proposed method with the traditional explosion protection function realization scheme.It proved that the proposed method can realize the flexible configuration of safety devices and design explosion protection equipment with different SIL and EPL,and provide an evaluation for EPL of new explosion protection technology.The method has better application prospects.(2)Propose a unified evaluation model for the safety and reliability of explosion protection functionsBased on the analysis of the traditional explosion protection technology defined by IEC60079,the explosion protection types are classified into isolated explosion protection and energy-limited explosion protection technologies from the three elements of explosion,and the reliability mathematical models corresponding to the two explosion protection principles are respectively discussed in the discussion of equipment failure modes.Keep the key parameters of the reliability model,but try to be as concise as possible to provide convenience for subsequent data collection.The model proposed in this paper plays a major role in quantitatively evaluating explosion protection functions.In the field application,the failure rate and hardware integrity level of different explosion protection types are established based on the reliability model and historical data.Finally,it can be applied to explosion protection frequency converters,The safety integrity level and equipment protection level of explosion protection equipment such as explosion protection motors and control systems.(3)A method for evaluating the spark ignitability of variable frequency drive shaft voltage discharge current for explosive atmosphere based on intrinsic safety theory is proposedAfter comprehensively considering the electrical safety and explosion risks that may occur during the connection between the inverter and the motor after the use of explosion protection electrical protection measures,the mathematical model of the shaft current of the inverter-fed motor suitable for the analysis of the explosion possibility is studied,and the inductance of the shaft voltage discharge is proposed.The discharge model and evaluation method of the capacitor composite circuit give out the explosion risk of the shaft voltage discharge through simulation and experiment,and give the safety criterion under the explosive atmosphere of different gas groups.Combining the explosion protection functional safety and reliability evaluation model with the research methods in this chapter,it can be extended and applied to the assessment of explosion protection functions and safety integrity levels of other potential ignition sources without explosion protection measures.