In electrified railway operation, it is easy to result in low-frequency oscillation if the electrical parameters of the locomotive and the traction network are mismatched. This will not only hamper the power supply protection of the traction network, but also lead to blocking of the locomotive’s traction system, posing severe threats to the safe operation of traction network and locomotive. To better suppress the oscillation, this paper presented an optimized oscillation suppression strategy and parameter design method. Firstly, after describing the equivalent circuit topology and control strategy of the vehicle-network system, a closed-loop small signal model of the system was modeled according to small signal theory. Then, on the basis of stability analysis, an optimized oscillation suppression method was proposed based on active damping control, aiming to improve the dynamic performance of the suppression strategy. As for the issue that excessively large coefficient for active damping control would influence the steady-state performance of the system, the minimum value of active damping control coefficient was determined according to Routh stability criterion. At last, the results of the test on time-domain simulation model verified the effectiveness of the optimized suppression method and the rationality of its parameter design.
According to figures provided by the European Commission, more than 20,000 people die each year when traveling in the European Union (Press release European Commission, 2021). In 2019, the EU average of road accidents was 51 deaths per million inhabitants, with significant differences between low and high accident rates. In the Slovak Republic, drivers with a driving experience of up to 5 years (approximately 25%) cause fatal accidents every year, while drivers who belong to this group make up only 11.6% of all drivers (Statistical overviews of the agenda of traffic accident in the Slovak Republic and complete statistics Ministry of the Interior of the Slovak Republic, 2022). One of the causes of this condition can be sought directly in driving schools. The main goal of the paper is to analyse the system of driving schools based on selected criteria in selected thirteen EU countries (Bulgaria, Czechia, Denmark, Finland, the Netherlands, Croatia, Lithuania, Latvia, Germany, Poland, Romania, Slovenia and Sweden), which show differences in numbers. People killed in traffic accidents and compare them with the system of driving schools in the Slovak Republic. The paper also looks for a link between the number of fatal traffic accidents in a given country and the driving school system.
Railroad engineering and operation, Industrial engineering. Management engineering
Introduction. Improving the traction and adhesion properties of freight electric locomotives is currently an urgent issue for the domestic locomotive industry. The increase in the mass and speed of trains enables to seek new ways and possibilities for realising the maximum tractive force of freight locomotives in order to meet the requirements of the rapidly developing transportation methods.Materials and methods. The authors carries out the analysis of existing theoretical and practical methods of adhesion control and developed the algorithm for controlling the wheelsets adhesion of a locomotive with asynchronous traction motors.Results. The authors concerning the tests analysis of a real electric locomotive, developed a mathematical model of the locomotive movement, which included algorithms for axial control of the tractive force with the redistribution of the tractive force between the axles. Calculations of a mathematical model of the movement of a locomotive with a train on a section with the redistribution algorithm both enabled and disabled, as well as with various settings of this algorithm, were carried out. The model also took into account the change in the adhesion coefficient of the wheels with the rails depending on the numerical order of a wheelset in the direction of travel, as well as the additional loading and unloading forces that arise in the undercarriage depending on the tractive force being realised. As a result of the calculations, obtained data showed good convergence with the test data of a real electric locomotive.Discussion and conclusion. The developed mathematical model allows evaluating the realisation of the tractive force of a locomotive as close as possible to that specified by the locomotive throttle under conditions of a changing adhesion coefficient and its heterogeneity under different wheelsets of the locomotive. The obtained results can be further applied in the development of promising freight electric locomotives with asynchronous traction motors.
As a key component of electric locomotives, the traction converter works for the DC to AC energy conversion through a large power insulated gate bipolar transistor (IGBT), thus exerting control over starting, braking and speed regulation of the AC traction motor. Its reliability is directly related to the operational safety of electric locomotives. Since the solder layer failure is one of the main failure modes of IGBT modules, it is very important to clarify the solder layer defect evolution law, for the sake of reliability of IGBT modules. In this paper, the solder layer of an IGBT module was firstly scanned by CT before and after putting into service of the electric locomotive. The statistical results showed that the number of solder layer voids in the IGBT module with different service mileages was in line with the Poisson distribution, of which the variance (λ) had a mapping relationship with the service mileage of the devices. Secondly, a multi-physical field simulation model of IGBT modules for electric locomotives was established, based on the statistical distribution law of voids and considering the initial defects, and the evolution inducements and law of random voids were studied by means of the strain mathematical description on the upper and lower surfaces of the solder layer. Finally, the relationship among void distribution, size and evolution rate was generated according to the energy-based fatigue lifetime model, which provided a basis for guiding optimal design and active maintenance of the devices.
The breakdown voltage is an important parameter for IGBT, and the breakdown voltage of the device is mainly related to the termination structure, so the research on the termination structure has always attracted attention. The termination structure of 1 700 V IGBT was designed in this paper. The termination technique combining field limiting ring and field plate could reduce the peak electric field on the device surface and improve the breakdown voltage. The termination structures with different field plate length and oxide thickness were simulated. Polynomial fitting and multiple regression were used to analyze the relationship between breakdown voltage and surface electric field distribution, the length of field plate on each ring and oxide thickness. Based on this, the breakdown voltage and surface electric field of the device could be predicted, and the time spending on termination design could be shortened. After adjustment, the breakdown voltage has achieved 1 927 V with 366 μm length on termination structure, and efficiency of the termination is 91.5%. The peak of surface electric field was effectively reduced and the surface electric field distribution was optimized.
Based on the Maxwell model calculation method of hydraulic damper dynamic characteristics, the calculation method of the dynamic characteristics of the hydraulic damper was improved by theoretical analysis, with the bench test, the improved algorithm was compared with the existing calculation standard, and the correctness of the improved method was verified. The results showed that, the calculation results are consistent for the bidirectional flow hydraulic damper, which the F-s indicator diagram is nearly symmetry; there are some differences between the two computational results for the unidirectional flow hydraulic damper, which are shown to be asymmetrical F-s indicator diagram. The improved algorithm is a universal method for calculating the dynamic characteristics of hydraulic damper.
The reliability of metro signal system is the decisive factor to ensure the safety, availability and maintainability. Aiming at the lack of signal system RAMS evaluation methods, based on vector data model and statistics analysis methods, CBTC interlock reliability index and sensitivity calculation formula was proposed, which was validated by the real example.
The development of modern railway equipment maintenance system was reviewed, detailed in the current condition and defects of EMU maintenance system, and the disadvantages of periodic maintenance such as insufficient repair, excessive repair, high risk of secondary disasters, and high cost of maintenance were pointed out. Then, the application of condition based maintenance (CBM) in EMU was analyzed and demonstrated. Lastly, the logic decision flow chart of EMU maintenance was proposed and the development trends of EMU maintenance system in the future were prospected.
A brief analysis of the physical and mechanical properties of materials, used in the construction of the rail bed, has shown that in scientific and technical literature there is scattered unsystematic information obtained under different physical conditions for bulk materials (gravel and sand). Unstructured data on the physical and mechanical properties of granular materials does not allow formulating a relatively complete dynamic theory for a wide range of static and dynamic loads, vibration acceleration and humidity conditions in relation to rail transport. In this article the authors formulate the problem of stability of the system “clayey soils in the main area - protective layer of sand cushions - ballast crushed stone prism” under the impact of harmonic oscillations on the basis of physico-chemical mechanics. Loam or clay belongs to isotropic visco-plastic media, sand and gravel - to disperse granular media. Filling the pore space of the gravel with weeds leads to the retention of precipitation and melt liquid. During deflation processes clogging of the gravel layer is increased. Despite the enormous practical value, properties of granular materials, until recently, practically not been studied. Under appropriate conditions this material may behave as a solid and as liquid and as gas. Each phase has unique properties that distinguish granular materials from all other substances. If the vibration field is applied to layer of gravel or sand, the energy of this motion is passed even through individual granules. As a result, with sufficiently high amplitude of jitter a phase transition occurs: the entire mass of granular material gets in motion, begins to flow due to reduction in friction between the particles and behaves as a kind of “granular liquid”. Fluid state of gravel stone occurs at much large values of the amplitude of vibration because of its angular shape. The result is a hydrodynamic instability, then convection starts and the vortices spontaneously appear.
Následující text popisuje vytvoření webové aplikace pro prohlížení digitálních mapových podkladů s možnosti importu externích dat, který by měl v základu sloužit pro zobrazení a analýzu dat udávajících pozici ze systému APRS (Automatic Packet Reporting System) na off-line mapě.
Railroad engineering and operation, Industrial engineering. Management engineering
Dual-power sourced rail heavy-duty track maintenance machines were proposed against the defects of the current diesel engine and hydraulic-driven mode. The advantages and application range of the electric/diesel hybrid on rail heavy-duty track maintenance machine were analyzed, and the technical difficulties were described. Finally, a brief introduction of electric/diesel hybrid 48-stones rail grinding machine was provided.
The proposed paper is focused on measurement and evaluation of supply chain performance in order to its sustainable improvement. The main goal is to suggest categorization of metrics and examine each category in order to verify whether companies exploit the full potential of measurement. The presented outcomes are based on preliminary questionnaire survey conducted among Czech companies.
Railroad engineering and operation, Industrial engineering. Management engineering
The choice of a suitable transport mode greatly affects the effectivity and profitability of realized transportation. Within the research conducted at the Department of Railway Transport, University of Žilina, was choosing the right mode of transport constructed by method of constructing matrix of benefits, or using selective diagram. Those methods largely objectify decision process and are supporting its optimization. Decision-making is performed on the basis of the assessment of the qualitative criteria predetermined for each particular transportation according to the type of goods.
Railroad engineering and operation, Industrial engineering. Management engineering
In order to enhance hardware reliability of distribute train electric control system, the signal integrity problems of high-speed digital circuit was simulated and studied. Simulation methods and tools were introduced, and with an example of DDR circuit, signal integrity simulation analysis of wave, matched resistance, crosstalk, and switching noise were discussed in detail. The simulation results and the test results were consistent which verified the reliability of the methods.
A novel modeling method for three-level traction converter was presented, which could complete all the working modes andmodes transferring simulation of the converters. This method was easy and distinct with few calculations for real-time simulation. Comparisonto the library models of Matlab/Simulink and application of hardware-in-loop simulation indicated the preciseness and reliability of theproposed modeling method.
By comparing laminar and turbulent models, the flow regime of water-cooling plate with straight channels was researched; the results showed that the average velocities were different in channels, and it was improper to set the flow regime of all channels with laminar or turbulent. The highest different temperature of IGBT installing place of water-cooling plate would be 6~9 ℃ to IGBT precise model compared with uniform layout heat source. The exact temperature field and junction temperature of IGBT would be got with precise model, which helped optimizing channel structure and improving heat transfer efficiency.