Secondary braking, by magnet

A revolutionary secondary brake, known as the Magnetarder, has been developed by Voith from Germany and Japanese retarder manufacturer Sumitomo Metal Industries (SMI). A joint venture was established in 2008 between the two companies to develop this technology.

The new technology is said to be able to provide the ideal solution for retardation in vehicles with the GVM between 7.5 and 16 tonnes. The Magnetarder has been developed as a combination between the Hydro dynamic retarders produced by Voith and the compact Permanent Magnet retarder currently sold by SMI on the Japanese domestic market.

The stator in the hydraulic retarder contains a number of maximum strength permanent magnets. These magnets are arranged in such a way that the opposing poles face each other. When the Magnetarder is switched off, the magnets are bridged allowing magnetic force to flow through the poles. However, when it has been switched on, the magnets are moved using compressed air to create magnetic forces flowing through to the rotor. Strong eddy currents are generated in the hydraulic fluid which retard the rotor.

The advantages of the Magnetarder include low tare weight and low heat generation. The new retarder is expected to be particularly useful for trucks powered by natural gas, as other retardation technologies are ineffective in CNG and LNG engines. The company says tests have demonstrated a 64% reduction in the use of service brakes in a 12 tonne truck.

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