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Principles of Energy Conversion
Published in Hamid A. Toliyat, Gerald B. Kliman, Handbook of Electric Motors, 2018
Hamid A. Toliyat, Gerald B. Kliman
Third-rail contact systems supply power through steel rails, usually alongside and somewhat higher than the running rails. Third-rail shoes, usually four per car, are mounted on insulating beams on the trucks. This system is optimum for highplatform subways, as it is out of reach of passengers in normal operation and no tunnel dimension need be increased for it. It is unsuited to services having street running or frequent grade crossings. While shoes on both sides of the car give some freedom in physical arrangement of the third rail, gaps occur at most switches and crossings. In the real world, with low and high third rail and broken shoes, motors running on these systems experience frequent power interruptions.
Rail – urban, suburban and regional
Published in Corinne Mulley, John D. Nelson, Stephen Ison, The Routledge Handbook of Public Transport, 2021
Heavy rapid transit (HRT) systems are found in the world’s major cities and are typified by systems such as the London Underground, the Paris Metro, the New York Subway and Hong Kong’s Mass Transit Railway (MTR). Generically known as Metro systems (despite the eccentricities of the Parisian system) or U-bahns in Germany, they have capacities of up to 60,000 passengers per hour, although the Hong Kong Mass Transit Railway achieves 80,000 per hour (White, 2002 – and also discussed in the case studies section). They are usually exclusively segregated, at least in the central city, although they may share tracks with other services in the outer suburbs. Category A rights of way may be provided by underground operation in the central area, either through shallow ‘cut and cover’ tunnels (also known as subways) or deeper tube tunnels. Alternatively, exclusivity may be provided by elevated rights of way, as with the Chicago Loop or the Sky Train services in Bangkok or Vancouver. They have full signalling, frequent stations (with spacings as low as 400 metres in central sections but more typically 1 km) and conventional platforms. Rolling stock is high capacity, with crush loads as high as 300 per car but more typically 150, and with a typical stock life expectancy of around 30 years. Trains are run in formations of at least 8 cars, usually in fixed formations, and have good performance in terms of acceleration and deceleration, with rates of 1 metre per second squared or more. This is assisted by the hump-back design of the track at stations. Trains are powered by electric motors. The electricity supply is typically up to 750 volts dc (direct current) and, given loading gauge constraints, usually delivered via a third rail. This requires frequent substations (typically every 3 to 5 km) but less electrical equipment on the trains. Trains have full crash worthiness and typically have a mass in excess of 1.42 tonnes per metre (De Leuw, Cather and Company, 1976), although more recent initiatives have seen attempts at light-weighting. White (op cit., p. 68) gives a typical weight for a heavy rail vehicle of 250 kg per passenger space compared to 125 kg for a bus. Full signalling is provided, with short blocks, and in the most advanced systems may be of the moving block type. Advanced systems will also have automatic train operation, a feature that in theory dates back to the Victoria line on the London Underground in 1968 (although the trains on this line have drivers). Early examples of fully automated systems with moving block signalling (or similar) include the Lyon Metro Line D (1992) and the Paris Metro Meteor Line 14 (1998), and some existing systems are gradually transitioning towards full automation, particularly where there is a simple route structure, as is the case for the Glasgow Subway, which plans to transition in 2021.
T
Published in Philip A. Laplante, Comprehensive Dictionary of Electrical Engineering, 2018
thermomagnetic process reaction between a metal oxide and aluminum with or without the application of pressure. thermomagnetic process the process of recording and erasure in magneto-optical media, involving local heating of the medium by a focused laser beam, followed by the formation or annihilation of a reverse-magnetized domain. The successful completion of the process usually requires an external magnetic field to assist the reversal of the magnetization. thermomagnetic recording recoding method used with magneto-optical disks. It involves first using a focused laser beam to heat the disk surface and then forming or annihilating magnetized domains. thermometer coding a method of coding real numbers in which the range of interest is divided into nonoverlapping intervals. To code a given real number, say x, the interval in which x lies is assigned the value +1, as are all intervals containing numbers less than x. All other intervals are assigned the value 0 (in the binary case) or -1 (in the bipolar case). thick lens lens inside of which internal ray displacements and beam profile evolution are too large to be neglected. thin film capacitor capacitor. See metal-insulator-metal laid along the railbed just outside the traction rails. This third rail is maintained at (typically) 600 volts DC by the railroad power supply, and contact is made to the locomotive by a shoe which slides atop the rail. Ground return is through the traction rails. third-harmonic generation the process in which a laser beam of frequency interacts with a nonlinear optical system to produce a beam at frequency 3. See also harmonic generation. third-order intercept (TOI) point this gives a measure of the power level where significant undesired nonlinear distortion of a communication signal will occur. It is related to the maximum signal that can be processed without causing significant problems to the accurate reproduction of the desired information (e.g., TV signal). Technically, the TOI is the hypothetical power in decibel-meter at which the power of the "third-order intermodulation" nonlinear distortion product between two signals input to a component would be equal to the linear extrapolation of the fundamental power. third-order susceptibility a quantity, often designated 3 , describing the third-order nonlinear optical response of a material system. It is defined through the relation P 3 = C 3 E 3 , where E is the applied electric field strength and P 3 is the 3rd order contribution to the material polarization. The coefficient C is of order unity and differs depending on the conventions used in defining the electric field strength. The third-order susceptibility is a tensor of rank 4 and describes nonlinear optical processes including third harmonic generation, four-wave mixing, and the intensity dependent refractive index. See also nonlinear susceptibility. Thomson, William (Lord Kelvin) (1824- 1907) Born: Belfast, Ireland Best known as a physicist who championed the absolute temperature system that now bears his name (Kelvin). Thomson did significant
Optimal energy management of a DC power traction system in an urban electric railway network with dogleg method
Published in Energy Sources, Part A: Recovery, Utilization, and Environmental Effects, 2021
Xiaojuan Hu, Shan Zhou, Tie Chen, Mohammad Ghiasi
A typical configuration of the AC-DC RTPSS is shown in Figure 3. As can be seen from Figure 3, substations are installed in the specified locations, including transformers and rectifiers. Also, transformers are responsible for reducing the voltage distribution network from 20 kV to 750 V. Besides, the rectifiers are responsible for converting the AC voltage into the DC voltage network. In every substation, there are two parallel rectifiers and a transformer to increase the reliability of the stretching. The third rail is responsible for transferring power from underground stations to the trains.
Dynamism of Parasite Capacitance of AC Electric Traction Line Inside the Railway Tunnels
Published in IETE Journal of Research, 2022
Ravi Kumaran Nair.C, Devender Kumar Saini, M. Jayaraju
Normally, the traction power to metro rails is fed through third rail in DC (mostly 750 volts). But in some metro transportation like Delhi metro rail corporation (DMRC), 25 kv ac OHE has been implemented [20]. OHE at 25 kv can be adopted for Broad Gauge (BG) tunnel rails, but it is not desirable for Standard Gauge (SG), since the clearances required for such a high voltage from the surrounding structures are the constraints.