One of the most important subjects of overhead contact line and pantograph system is to reduce the contact loss of pantograph in high-speed operation. In this research, the relation between the wave motion of contact wire and the contact force fluctuation of pantograph is studied; the contact force fluctuation in a hanger span cycle is analyzed; and methods to reduce the contact force fluctuation are proposed. It is shown that the contact force fluctuation of pantograph in high-speed operation is mainly caused by the incident wave of contact wire that is generated by the unevenness of contact wire and is reflected at hangers. This influence becomes extremely large when the train speed is close to the wave velocity of contact wire. Increasing the wave velocity of contact wire or decreasing the reflection factor of wave motion at hangers is expected to effectively reduce the contact force fluctuation.

Undulating wear of overhead rigid conductor line causes serious trouble, such as extreme wear of contact line and contact strips of pantograph. In order to analyze the mechanism of wear and propose countermeasures against this problem, we have carried out investigation of wear characteristics of real lines and excitation tests of pantograph. Based on the results of these tests, this paper reports the condition to easily generate undulating wear, discusses the mechanism of wear process and proposes some countermeasures to prevent undulating wear.The unevenness measuring device used in this study consists of two pairs of laser sensors to reduce measurement errors due to the vertical vibration of measurement vehicle. The unevenness of sliding surface of rigid conduction line was measured accurately and continuously with this device. The measured undulating wear was characterized as follows. The sliding surface of conductive rail is roughened with serious arc spots caused by contact loss of pantograph; the maximum amplitude of the unevenness (peak-to-peak) is about 0.4 mm (Fig. 1); the wavelength is about 12 cm, which is equivalent to half the distance between two contact strips of pantograph; and undulating wear tends to occur in the section where trains are in powering at about 45 km/h (Fig. 2) and the deviation of rigid contact line is larger than 50 mm.

The unevenness of contact lines is one of the factors that considerably influences on the dynamic characteristics of current collection system. In order to analyze the influence of the contact line unevenness on the fluctuation of the contact force between contact line and pantograph, an instrument was devised to measure the unevenness of contact lines accurately and continuously. The instrument consists of two pairs of laser sensors for the purpose of reducing measurement errors by the vertical vibration of measurement vehicle. This paper describes the measuring method of contact line unevenness, reports some examples of the measurement of real lines, and proposes a method to evaluate the conditions of overhead equipment.

Rail corrugation is a phenomenon in which roughness patterns of approximately regular wavelengths are formed on the rail running surface by trains running, and causes the vibration and the noise. Therefore, in this paper, we analyze the amplification factor of roughness amplitude using a model that takes into consideration the interaction between the track and the vehicle, and clarify the growth mechanism and the wavelength determination mechanism of the rail corrugation. As a result of the theoretical analyses, it is indicated that the essential factors of growth of the corrugation are (1) interference of rail wave motion between the front and the rear wheels of a bogie of the vehicle, (2) anti-resonance phenomenon of the elastic support of the track system, (3) anti-resonance phenomenon of the total system of the track and the vehicle, and (4) anti-resonance phenomenon of the vehicle system. In addition, as a result of examing the rail corrugation measured on the commercial lines, it is confirmed that the causes of the corrugation occurrence are the above mentioned (1),(2) and (3) factors, and that the measured wavelengths almost agree with the theoretical values.

One of the most important subjects for the current collection system of high-speed railways is to reduce the contact force fluctuation between contact line and pantograph. The unevenness of contact line is one of the factors that considerably affect the dynamic characteristics of contact line and pantograph system. This paper describes the methods to estimate the static installation quality of contact lines by calculating dynamic characteristics and reports some examples of the estimation of real line conditions.The flowchart of the dynamic estimation method of contact line is shown in Fig. 1. The dynamic characteristics, such as contact force fluctuations of pantographs and motion of contact lines, are calculated from the measured unevenness of contact wires, and the calculated results are diagnosed quantitatively. The static parameters, such as the tension of contact wire and the longitudinal force working on hangers, are derived from the unevenness of contact wire between hangers. The estimation conditions, such as pantograph type and train speed, are set at actual values of the section under estimation.In order to verify the accuracy of the estimating method, the calculated results based on a real unevenness data are compared with the measured results in the same section. Fig. 2 shows a comparison between calculated results and measured results of the maximum strain of contact wire at a support point. The calculated values agree well with the measured values. It is also confirmed that the uplift of contact wire and the contact force of pantograph are similarly in agreement.An example of dynamic estimation of contact line is shown in Fig. 3. In this case, since the calculated values do not exceed the This estimating method is useful for quantitative diagnose, such as detection of abnormal equipment, inspection after construction work and assessment of the amount of repair. This method is expected to contribute to efficient maintenance of contact lines for high-speed operation.

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