Study On The Theory And Application Of The Intrinsically Safe Switch Power Supply

The actual needs of digital mine construction and the development of the mineinternet of things technology made the number of the underground detecting andmonitoring equipment such as intrinsically safe sensor and intrinsically safe controllergreatly increase. So demands for high power intrinsically safe power supply werestrongly proposed. Some research on basic theory of intrinsically safe switch powersupply was did in this thesis, and some approaches for improving the power wereproposed, which had important theoretical significance and practical value for thedesign of high power intrinsically safe switching power supply.With deep research for intrinsically safe circuits, new research objects andcontents emerged. In order to make clear of the relationship between these researchesand original system and integrate into original system concepts, structural system ofthe safety system based on the original was refreshed in this thesis. Some conceptssuch as primary intrinsically safe power supply, secondary intrinsically safe powersupply, front-end protection mode, back-end protection mode, natural discharge modeand cut-off discharge mode of spark discharge were proposed and their structures,characteristics and other aspects were described in detail.Mathematical models of CL compound circuit and LC compound circuit inopen circuit and short circuit under natural discharge mode were established and thechange law of spark discharge energy and power under different electrical parameterswas also researched in this thesis. From the simulation, it shows that, increasing theinductance value could reduce spark discharge current, spark discharge energy andpower, as well as the peak current time which is conducive to enhance the safetyperformance. Non-oscillatory situation under the bigger inductance value is moreconducive to safety performance than oscillatory situation. In addition, sparkdischarge characteristics of EC circuit and the effect resulting from power potential onspark discharge were analyzed in this thesis. Based on energy equivalent principle,EC circuit was equivalent to a simple capacitive circuit based on the principle ofenergy equivalent so as to make use of capacitance minimum ignition curve undernatural discharge mode to determine its security.Spark discharge mathematical models of capacitive circuit and CL compoundcircuit were established，and the mechanism and rules of intrinsically safe circuitspark discharge were studied under cut-off discharge mode，besides, the influence of the electrical parameters such as cut-off time on the intrinsically safe circuit’s safetyperformance was quantitatively analyzed. The study found that the regularity of thespark discharge was significantly different between the cut-off discharge mode andthe natural discharge one. For capacitive circuit, under natural discharge mode, thespark energy eventually reached a steady state, and the spark discharge energy insteady state was proportional to the capacitance value. While under cut-off dischargemode, the spark energy was approximately exponential to the capacitance value. Thespark discharge energy tended to a steady-state value with the capacitance valuetending to infinity. For the CL composite circuit, under natural discharge mode, thetime of spark power up to the maximum would be longer with the inductance valueincreased, and the maximum would decrease. The spark energy reached a steady stateeventually which has no relationship with the inductance value. But under cut-offdischarge mode, the time of spark power up to the maximum would not be changedeven the inductance value increased, and the maximum would decrease. The sparkenergy decreased monotonically with the increasing of the inductance value. Finally,experiments have been carried out to verify the conclusion of intrinsically safeperformance analysis.Through analyzing factors that affected the spark discharge energy, the methodswere given in this thesis such as increasing the switching frequency, shortening thecut-off time and using virtual soft-switching which could improve the capacity ofintrinsically safe supply. These methods were used in practical intrinsic safety powerwhich had been certificated by Shanghai Research Institute Test Center of China CoalTechnology&Engineering Group Corp.A cut-off self-recovery protection circuit structure which was suitable forhigh-power intrinsic safety power supply was designed, and the three-level flybacktopology was selected to design intrinsic safety switching power supply, which meetsthe designing requirements through the simulation and experimental analysis.