Although other methods have been studied recently, the regenerative brake system has been contributing to reduced energy consumption on electric railway vehicles for over 30 years. However, there are a lot of problems associated with the system, such as regeneration being cancelled out by wheel slide and trolley voltage conditions, decreases in electric braking force in the higher speed ranges, and restrictions on regenerative power determined by power supply circuit impedance. In order to utilize and recycle braking energy and secure a steady regenerative load, we selected lithium ion batteries to store electric energy and developed a rechargeable lithium ion battery (600 V system) for use on electric railway vehicles as one of the prominent alternatives. In this paper, we report on an energy recycling contact-wire-less tramcar that uses the rechargeable lithium ion batteries and show the tramcar's performance and characteristics of the battery as developed. The battery under development has demonstrated excellent performance in terms of energy and power density, efficiency, 500 A charge and discharge current, internal resistance and maintenance work.
How to stabilize power sources to minimize voltage drops, power load fluctuations, and regenerative power lapses has been a key problem area in DC feeding circuits. Energy storage media that use power efficiently and eradicate such problems have been attracting interest, with several energy storage applications, including batteries and flywheels, having already been investigated. A wide range of large-scale electric double-layer capacitors (EDLCs) quickly charged and discharged, offer durability, maintenance-free features, low pollution and high efficiency levels, have been developed. Our research compared batteries with EDLCs in terms of their ability to charge/discharge at DC 75V. For the latest study, we produced a prototype DC electrified railway energy storage system that consists of EDLCs, a diode bridge rectifier, a chopper system, and a pulse width modulated (PWM) converter, useful information being obtained from charge/discharge tests. This paper describes the characteristics and results of the energy storage system experiments.
The advances made in optical transmission and measurement technologies in recent years have expedited the development of optical networks and current sensors. This paper outlines the characteristics and special features of optical fiber sensors, describes the current measuring principles of optical current transformers (CTs) that utilize the Faraday (magneto-optic) effect, and introduces examples of their railway electric power system applications—the fault detection of Shinkansen changeover switches and the measurement of DC currents.
This paper reports on the basic configuration of the railway static power conditioner (RPC), a static voltage compensator for AC electric railways. 20 MVA / 60 kV RPCs started commercial operation in 2002 at each substations on the newly extended Tohoku Shinkansen. The results of operational test indicate that an RPC can accommodate single-phase loads such as those of PWM-controlled Shinkansen and thyristor phase-controlled Shinkansen, handle the exciting rush current of transformers, as well as compensate for harmonics. The voltage fluctuations on the three-phase side were succcessfully controlled by the RPCs.
The vibration of overhead contact line caused by a patograph passing through an overlap section propagates on the overhead contact line and reflects at an anchor mast. The reflection wave thus generated returns to the pantograph and worsens the performance of current collection. To reduce the reflection wave with a damper, we used a model to calculate the constant and installation point for the damper, which were examined with a pantograph/catenary simulation program to prove that the installation of a damper decreased the contact loss ration and contact force fluctuations. This paper introduces the simulation that uses the results of theoretical calculation to reduce the reflection wave using a damper, evaluates the effectiveness of the damper from the viewpoint of contact loss ratio and contact force fluctuations.
Dead sections are installed in the overhead contact line systems between power feeding sections having different voltage phases on JR's AC electrified narrow-gauge lines. There have been cases where train speed-up has been restricted because high bending strain values tend to occur in the contact wire at the entrance of the dead section when a pantograph passes them. To reduce this strain, the author considered the sliding surface level differences caused by tension at both ends of the dead section and prepared an experimental dead section that reduced these differences. Pantograph running tests on this dead section confirmed a reduction in contact wire strain.
To measure the contact force between a pantograph and contact wire the author is proposing to use a new inversion method, the distinct feature of which is to reduce restraints on the sensor arrangement to facilitate contact force measurement. The contact force is calculated using the convolution between the sensor output and impulse response function, which is defined as the relationship between the former and the contact force. To achieve sufficient levels of precision, high order vibration modes of the panhead have to be taken into consideration by applying a pseudo-inverse matrix. The author has confirmed the accuracy of this method by numerical calculations and an excitation test on a currently-used pantograph.
The unevenness of contact lines is one of the factors that greatly influence the dynamic characteristics of current collection systems. In order to analyze the influence of the contact line unevenness on the contact force fluctuations between contact lines and pantographs, an instrument was devised to measure the unevenness of contact lines both accurately and continuously. The instrument consists of two pairs of laser sensors to reduce measurement errors caused by the vertical vibration of the measurement vehicle. This paper describes a way of measuring contact line unevenness, reports on some results obtained from measuring actual lines, and proposes a method to evaluate the conditions of overhead contact lines.
Environmental management system (EMS) has proven to be very effective in providing railways with solutions to environmental problems. After the investigation and analysis of the EMSs in about 20 organizations, including those in the railway industry, it was found that one of the most important factors in establishing them are the methods of environmental impact estimation. This paper discusses methods used in a wide range of organizations. On the basis of the results, we have been able to propose a new environmental impact estimation equation that is applicable to a number of industries, including railways.
There has been a growing demand for a low-cost, low-maintenance signaling system on cash-strapped secondary lines. To meet this demand, we have developed the new Computer and Microwave Balise-Aided Train Control System (COMBAT). Specific features of COMBAT are the application of microwave radio balises for train detection and centralized interlocking and block functions. This paper introduces the system configuration, its basic functions, and its benefits.