| This dissertation is devoted to a study of the influence of electromagnetic disturbance from a shearer upon electromagnetic environment in fully-mechanized mining faces. In view of the specific characteristics of electromagnetic environment in coal mines, the induced mechanism of electromagnetic disturbances from a shearer are analyzed.For driving characteristics of shearer traction and cutting motor units, harmonic and transient disturbance and continuous radiation disturbance are studied respectively. According to the variable frequency control principle harmonics produced by shearer traction unit with different control methods have been analyzed deeply in theory. Based on the actual parameters of traction system, simulation models are built and simulation results are given. When a shearer cutting motor is swithching on or off, transient disturbances produced by the cutting motor are analyzed and caculated, and switching off a cutting motor is also simulated by electromagnetic transients program (EMTP). Radiation models for transient current impulse is established based on traveling wave antenna theory and nonsinusoidal pulse electromagnetic radiation theory, and radiated electromagnetic fields of transient impulse are analyzed by simulations.Based on a large number of electromagnetic radiation data measured in underground coal tunnels, the radiated disturbance from a shearer is studied by an analogy method.Some value results for radiation disturbance levels are obtained. According to the electromagnetic wave propagation theory in a coal mine, the electromagnetic wave attenuation rules are analyzed in a coal tunnel and a coal mining tunnel, and the simulation models are established by using the finite element method. The conduction coupling model and radiation coupling model are built in coal mines.and the mechanisms of coupling models are analyzed. |
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