| At present,Various kinds of electrical equipments used for detection,control,monitoring,and communication are ubiquitous in coal mines,and the electrical equipments must rely on safe and reliable power supplies for normal operation.The mining intrinsically safe power supply has the advantages of high safety,low cost,small size and light weight,so it has became a hot topic for experts and scholars in recent years.The thesis is mainly to optimize the research of mining intrinsically safe power supply,especially for its overvoltage-overcurrent protection sequence and dual protection string and redundancy.I design a shutdown protection circuit with automatic recovery and an overvoltage protection circuit with a switching transistor as MOSFET.The purpose is to prepare for optimization studies.In order to optimize the selection of overvoltage and over-current protection sequences,I establish an intrinsically safe spark discharge equivalent model to determine the factors affecting intrinsic safety performance.The overcurrent and overvoltage protection circuits we designed are used as test circuits to simulate the protection performance of the two protection sequences in the case of overvoltage,overcurrent,overvoltage and overcurrent at the same time and they are studied with the characteristics of the protection circuit.In the double protection circuit string and parallel redundancy optimization,the concept of fault is introduced,and the over-current protection circuit is as a test circuit.Then we simulate whether it is a misbehavior or not when the two redundant intrinsically safe power supplies are not required to be protected and whether it plays a protective role or not when asked for protection.The study founds that:the characteristic of overvoltage protection circuit determines the choice of protection sequence,except overvoltage protection circuit is the short circuit type,overvoltage-overcurrent protection sequence for intrinsically safe power has higher safety performance.The type of the protection circuit switching tube determines the choice of dual redundant mode.For the type of the MOSFET’s circuit,the dual protection circuit series of intrinsically safe power supply has higher safety performanceFinally,based on the optimization conclusions,an "ia" protection grade intrinsically safe power supply is designed. |
