ADD systems, a necessity in high-speed transport

The TSI adopted on April 26, 2011 by the European Commission stipulates the need to equip the electric traction units with an automatic dropping device of the pantograph. It is still to be debated the compulsory regulation according to which the electric locomotives designed for a maximum speed of more than 100 km/h would be equipped with such a system that lowers the pantograph in case the contact wire is damaged.

To avoid the wear of the pantograph-catenary system, the black lead is used in the construction of collector shoes. “No other contact material better than carbon can ensure a longer life expectancy of the contact wires”, believes Herbert Fichtner, Manager of SBI-S (Schunk Bahn- und Industrietechnik GmbH – Salzburg).
Locomotive manufacturers are doing their best to install performing pantographs that would meet the safety and interoperability demands and equipped with damage protection systems. “In case the contact is not good enough (frost, insufficient contact force), the pantograph, more precisely carbon strips, will be damaged. The mechanical design of the pantograph has to permit that the unsuspended mass (next to the catenary) will be as light as possible. This is a very important principle for high-speed where it is recommended to use an automatic dropping device to avoid the wear of the catenary in case the pantograph slider is damaged”, points out Peter Honegger, Director of Sales and Marketing, Bombardier.
Pantograph manufacturers use a “pneumatic automatic dropping device in case of an unwanted railway incident at the level of the catenary”, called ADD System (Automatic Dropping Device). “A manufacturer famous worldwide that provides an innovating pantograph is Schunk Group which, through its subsidiaries in Austria and Sweden, is also the father of the electric locomotive pantographs manufactured under the license of the Swedish ASEA by Electroputere. With the WBL pantograph, Schunk manufacturer provides a protection solution by using the ADD system, a pantograph whose lightness and optimal aerodynamic form guarantee the best performance in exploitation, while the individual suspension of the pantograph slider guarantees an excellent contact behaviour. Currently, there are around 10 electric locomotives in Romania, all operated by CFR CĂLĂTORI and equipped with such Schunk pantographs. The locomotives are authorized to also run in Bulgaria, Hungary and Serbia”, declared PhD Eng. Adrian Zanfir, Director of Production,  Schunk Carbon Technology Romania.
By using this system, when an event occurs such as the accidental brake of the graphite collector shoe, the total wear after a too long period of exploitation or the brake of the catenary from different reasons, the pantograph receives an automatic dropping command, interrupting the direct contact with the catenary and ensuring its protection, thus helping to reduce structural costs both for the train and for the infrastructure, as well as operation costs due to traffic interruption.
This system has a very short reaction time: in just one second, the pantograph has to drop 20 cm below the catenary. During every raising action of the pantograph the electric control of the ADD-system must be switched of for 15 to 20 seconds. This is the time when the system needs to fill with air pressure. If the electric control is not switched off during this time, the pantograph will not raise, because the electro-pneumatic pressure switch does not have enough pressure. “If more than one pantograph is in the operating position and the first pantograph is damaged, the signal of the first pantograph will be used to lower the second pantograph. For this function, the electric signal of the pressure switch will be used to switch the electro-valve to the next pantograph that will command the lowering of the second pantograph”, said Herbert Fichtner, Manager of SBSI-S.
In Romania, a traditional pantograph manufacturer is Electroputere Craiova, providing equipments for more than 90% of the Romanian locomotives. “Our pneumatic EP3 series pantographs have a pressure delivery valve installed in the engine room for regulating the contact force in order to avoid the formation of electric arcs and consequently the wear of the pantograph and of the catenary”, declared Gheorghe Grămadă, Director Locomotives, Electroputere SA.

[ by Teodor Turcu ]
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