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Products and solutions, 2001-04-23, 02:00 AM

High-tech material for high-tech rail system

Transrapid uses electrical steel from EBG

The construction of the Transrapid line in China between Shanghai-Pudong international airport and the Lujiazui financial center of the Chinese seaport not only represents a breakthrough for a completely new form of transport, it also offers lucrative prospects for electrical steel producer Bochumer EBG Gesellschaft für elektromagnetische Werkstoffe mbH: some 13,000 metric tons of electrical strip will be needed to ensure that the high-speed maglev train achieves its planned running speed of 430 km/h on the 30 kilometer route. Electrical strip is the material used to make the so-called longstator motor, the Transrapid`s central propulsion component. For this application EBG has developed a special, functionally optimized electrical strip variant.

EBG is the world`s biggest manufacturer of grain-oriented electrical steel, and worldwide number two in non-oriented grades. The product is used wherever electrical energy is generated, transformed or converted into mechanical energy. Grain-oriented electrical steel is mainly used in power, distribution and small transformers or for signal transmission. Non-oriented electrical strip is found in generators or electric motors, to name just two examples.

The feedstock for this material is hot-rolled strip with a very low carbon content and a silicon content of up to 3.5 percent. After cold rolling, the non-oriented strip is subjected to recrystallization annealing in continuous furnaces, during which the microstructure is adjusted to give the material the required electromagnetic properties. The magnetic properties of grain-oriented strip are generated by laser surface treatment following annealing. The reactions which take place in the material during annealing can be controlled via the annealing temperature, annealing speed and annealing atmosphere.

The primary objective when developing new electrical steel grades is to minimize the hysteresis loss associated with any electromagnetic process and to achieve high polarization values. The lower the hysteresis loss, the lower the energy required to run the equipment in question. For the Transrapid`s longstator motor, EBG has developed a functionally optimized electrical steel grade with a magnetic reversal ratio of six watts per kilogram. Moreover, the material is provided with a self-bonding insulating coating.

The electromagnetic propulsion of the Transrapid is provided by a longstator linear motor located not in the vehicle but in the guideway. In principle it operates like a rotary electric motor whose stator has been cut open and stretched out. In contrast with conventional electric motors, this gives rise not to a rotating but to a traveling magnetic field which pulls the vehicle along.

Each of the stators is around 1,030 millimeters long and composed of 360 thin plates of EBG non-oriented electrical steel. The coating applied by EBG is used to bond the plates to form laminations. Bonding in this way avoids negative influences on hysteresis loss, and thus efficiency, which could be exerted by welding, riveting or clamping. Power is supplied for the traveling magnetic field via shielded cables fixed in grooves in the laminations. Some 200 metric tons of the EBG material are required for each kilometer of a Transrapid line.

For further reference: ThyssenKrupp AG, Trade Press, Bernd Overmaat Tel: +49-211-824-36012, Fax: +49-211-824-36035 e-mail: overmaat@tk.thyssenkrupp.com

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