Beginning with the rise of rail transport, the braking of a train acts via the wheel. The adhesion force between the wheel and the rail is one of the determining factors when the braking had its greatest impact. However, for high-speed trains (speed to 350 km/h) with heavier loads on the axle and more complex functions in reduced mounting space, the conventional braking systems relying on the adhesion force between the rail and the wheel are no longer adequate. Firstly, the braking distance increase is unusable. Secondly, the weather dependence of the braking distance is entirely unsuited. Thirdly, it requires of a braking system that will perform the profitable braking in the event of failure of the brake based on the adhesion force between the wheel and the rail.
The electrodynamic braking of trains is of particular importance for high-speed railway transport from theoretical and technical perspectives. Braking methods used for high-speed trains should ensure compatibility and redundancy of braking systems. They include a mechanical method (based on adding frictional disks to wheelsets), as well as magnetic braking, which is being currently implemented and based on eddy currents. High-speed trains have AC/DC engines, for which the principles of electric braking can be applied. Electrodynamic braking is of particular importance for high-speed transport using linear motors and developing the speed of 400-500 km/h. These traction rolling stocks will not have commonly used bogies. The tests in this area were being conducted in Japan and Germany in the last years.
Tests are also carried out to obtain more silent braking. Deutsche Bahn is speeding up the Europe-wide introduction of whisper brakes: the “Europe Train”, which has been traveling throughout Europe since December 2010, arrived in Berlin in April this year after putting a new type of whisper brake – the LL block – through its paces before it goes into series production. Made up of various types of freight car, carrying all kinds of cargo and commissioned by several European rail operators, the test train, which is being monitored by engineers and technicians, will have covered a total of 200,000 kilometres before the test program comes to an end at the beginning of 2012.
The LL brake block has the potential to halve rail noise produced by conventional freight trains. Unlike the K block, which also reduces noise levels by half, the LL brake block can be retrofitted to an existing fleet at significantly reduced cost.
by Elena Ilie
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