Design of intrinsically safe power supply

Aiming to make a high power direct current supply safely used in coal mine production, this paper made a deep research on characteristics of intrinsically safe power supply, using the mathematical model established according to coal mine intrinsic safety standards. It provides theory support for the application of high power intrinsically safe power supply. The released energy of output short circuit of switch power supply, and the close related factors that influence the biggest output short-circuit spark discharge energy are the theoretical basis of the power supply. It is shown how to make a high power intrinsically safe power supply using the calculated values in the mathematical model, and take values from intrinsically safe requirements parameters scope, then this theoretical calculation value can be developed as the ultimate basis for research of the power supply. It gets the identification method of intrinsically safe from mathematics model of intrinsically safe power supply characteristics study, which solves the problem of theory and application of designing different power intrinsically safe power supply, and designs a kind of high power intrinsically safe power supply through this method. energy, flyback

Equivalent-resistance based on the analysis of inductor-disconnected discharge behavior for intrinsic safety Buck converters

An Equivalent-Resistance based Analysis Method (ERAM) was proposed, which can convert the Inductor-Disconnected Discharge (IDD) behavior of the Intrinsically Safe Buck Converter (ISBC) into that of an Equivalent Simple-Inductive-Circuit (ESIC). According to the inductor disconnected equivalent circuit corresponding to the most dan- gerous operating case of the converter,the arc discharge time and the variation of out- put-voltage during the IDD were deduced based on the simple current linear attenuation model.According to the energy equivalence,the equivalent inductor-current of the ESIC was obtained.It is pointed out that although the inductor-current of the Buck converter is much lower than that of the published ignition curve,ignition still occurs and the ignition ability is strengthened with increase of the output capacitance.The proposed analyzing method is verified by the experiment results on IEC standard spark ignition apparatus.

Application of a novel detection approach based on non-dispersive infrared theory to the in-situ analysis on indicator gases from underground coal fire

Coal mine fires,which can cause heavy casualties,environmental damages and a waste of coal resources,have become a worldwide problem.Aiming at overcoming the drawbacks,such as a low analysis efficiency,poor stability and large monitoring error,of the existing underground coal fire monitoring technology,a novel monitoring system based on non-dispersive infrared(NDIR)spectroscopy is developed.In this study,first,the measurement principle of NDIR sensor,the gas concentration calculation and its temperature compensation algorithms were expounded.Next,taking CO and CH_(4) as examples,the liner correlation coefficients of absorbance and the temperature correction factors of the two indicator gases were calculated,and then the errors of concentration measurement for CO,CO_(2),CH_(4) and C_(2)H_(4) were further analyzed.The results disclose that the designed NDIR sensors can satisfy the requirements of industrial standards for monitoring the indicator gases for coal fire hazards.For the established NDIR-based monitoring system,the NDIRbased spectrum analyzer and its auxiliary equipment boast intrinsically safe and explosion-proof performances and can achieve real-time and in-situ detection of indicator gases when installed close to the coal fire risk area underground.Furthermore,a field application of the NDIR-based monitoring system in a coal mine shows that the NDIR-based spectrum analyzer has a permissible difference from the chromatography in measuring the concentrations of various indicator gases.Besides,the advantages of high accuracy,quick analysis and excellent security of the NDIR-based monitoring system have promoted its application in many coal mines.

Analysis of Discharge Spark Energy in Buck Converter of a Continuous Mode of Inductive Current

The basic idea of intrinsically safe circuit and the discharge spark in the Buck converter in the explosive at- mospheres were introduced. The Buck converter is the main topological structure of the switch type of intrinsically safe circuit, which has two working modes: continuous inductive current (CCM — continuous conduction mode) and dis- crete inductance current (DCM — discontinuous conduction mode). The operating state of the continuous inductive current mode is analyzed in detail and the energy of discharge spark in various operating modes is discussed. The total energy will decrease with the increase of switch frequency, in a switching cycle; the discharge spark energy has a maxi- mum and a minimum value. Therefore, the Buck converter has smaller discharge spark energy than the linear power circuit and the switch type of intrinsically safe circuit can enhance the output power and the conversion efficiency of the intrinsically safe power.

Analysis of low energy arc discharge characteristics based on dynamic V-A characteristics model

Low energy arc discharge characteristics was analyzed based on dynamic V-A characteristics model. It draws conclusions that discharge time relates to the source voltage and the product of inductance and stable current, discharge time will increase when the source voltage increases; current reduce rate is in inverse proportion to the value of inductance; arc resistance when the arc occurs is the ratio of minimum arcing voltage to stable current. It also gains the expressions of arc resistance and arc power, arc resistance and arc power both increase as the source voltage increases and decrease as the value of inductance increases. Conclusions above mentioned are helpful to design intrinsically safe circuits.