| The local fans are indispensable and important equipments for the mining drainage ventilation and gas exhausting. Many important tasks are undertaken by local fans such as providing fresh air for heading face, draining gas and bug dust, improving condition of working circumstance, exhausting gas after gas accumulation and so on. Their running reliability and operating flexibility directly affects the safe production in underground. For a long time, the control apparatus for local fans are out of date with unadvanced technology, uncertainty performance, imperfect function, dispersing apparatus, difficult maintenance in our country, which are unable to meet the requirement of continuous ventilation and safe discharging gas in heading face. The situation has been severely restricting the development of the safe production technology of our coal mine. Therefore, it is very important in practical terms to develop the integrated control system of multi-local fans in underground heading faces.In this thesis the PLC technology has been applied to integrated control system of multi-local fans in underground heading faces. Combined with the protective technology in power system and frequency control technology, the control scheme of the integrated control system of multi-local fans in underground heading faces is proposed and hardware circuit has been designed, the software is compiled, the system is debugged. It has been shown by experiment results that the control strategy and protective methods are availability and utility, which are able to meet the requirement of continuous ventilation and safe discharging gas in underground heading faces.According to the field requirements, the control scheme of integrated control system is proposed which can meet the requirements of multi-local fans in underground heading faces, realizing the function of exhausting gas with frequency conversion, and the protective circuits for motors are designed and the technical characteristics are established in the system. It has been shown by experiment results that the control scheme is exactitude, the protective circuit is reliable and the technical index is advanced .A PID adjuster of gas density in the mixing place of full wind pressure within PLC is designed. The controller can regulate local fan's speed by correcting the measure value and the value in advance of gas density through real-time controlling the output voltage and frequency of transducer. It makes the wind of local fan self-regulating and the value of gas density steady at the scheduled value, so as to exhaust the gas safely.A new type of integrated system controlled by SIMENS S7-200 PLC has been designed, which performs the protective functions of earth leakage lockout, current fault, voltage fault and so on. The two equipments are hot standby each other and have flexible conversion with the reliable function of test and the advanced redundancy mode of control.The interface between human and integrated system is also developed which is fit for the mining production and the technical characteristics of PLC. The CPU control frequency convertor with serial communication. The parameter input mode combining BCD dial plate with LCD panel is proposed to improve the usable operation of worker, decrease the time to find and get rid of the existing fault and boost the productivity in underground.It has been proved by the testing and running results that the designing methods and strategies are right and practical. As a result, the system developed in this thesis can greatly improve the continuity of drainage ventilation and safety of gas exhausting, which can guarantee the safety of coal mine. |
