| As the key component of traction power supply system of electrified railway,the electric conductivity of pantograph Current-carrying friction pair(hereinafter referred to as friction pair)has always been the key point in the development of electrified railway.in the actual operation of pantograph mesh,the contact resistance of the pantograph mesh fluctuates constantly and the electrical conductivity of the friction pair changes constantly.Therefore,it is necessary to study the comprehensive characteristics of the contact resistance and the electrical conductivity of the friction pair.this thesis in view of the actual operation of the Pantograph-catenary,Pantographcatenary contact pressure fluctuating objective facts,design,launched a related contact pressure fluctuation in the experiment,explores the general optimal static contact pressure,influence of initial current,running speed,amplitude of contact pressure fluctuation component and frequency of contact pressure fluctuation component(fluctuation frequency)on contact resistance characteristics(including static characteristics and dynamic characteristics).Based on the experiment,the static characteristic law of the contact resistance is obtained,and its cause mechanism is analyzed.in order to describe the dynamic characteristics of contact resistance quantitatively,the concept of stability coefficient of contact resistance was proposed to characterize the overall relative fluctuation degree of contact resistance relative to its mean value,and the fractal theory was introduced to reflect the local absolute fluctuation degree of contact resistance with the dimension of contact resistance box(fractal dimension).Based on the experiment for the rule of the dynamic characteristics of the contact resistance,found that the contact resistance stability factor with the initial current,the amplitude of pressure fluctuation component increases,decreases with increasing speed,along with the increase of the frequency of the wave decreases slightly,contact resistance box dimension with the pressure pulsation component amplitude,speed increases,decreases with the increase of initial current,basically remain unchanged,with the increase of the frequency of the wave skateboard microscopic surface morphology analysis,found the Pantograph-catenary vibration,the Pantograph-catenary arc,Pantograph-catenary wear is the main impact causes.Based on the above characteristics of the contact resistance research,the establishment of a comprehensive evaluation on the conductivity of the friction pair contact system,puts forward the comprehensive evaluation index,with expert investigation method and entropy weight method of combination of subjective and objective method for each division index comprehensive evaluation index weight has carried on the rational distribution,to the comprehensive evaluation index quantitative characterization of the friction pair contact electrical conductivity.Different operating conditions will lead to different degree of change of contact conductivity and contact conductivity stability of friction pair,and then comprehensively affect the contact conductivity of friction pair.Results show that the friction pair of contact conductivity with the increase of initial current,the amplitude of pressure fluctuation component and variation,along with the increase of running speed,wave frequency and get better,the speed relative to the largest,the influence of the initial current and the influence degree of the pressure pulsation component amplitude basic quite,and influence the frequency of the wave relative to minimum,almost to zero.It is found that the main reasons for the variation of the contact conductance of friction pairs are the vibration of the pantograph,the arc of the pantograph and the temperature rise of the contact surface.This thesis has 32 figures,12 tables and 90 references. |
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