In order to reduce the braking burden of traditional friction brakes (such as drum brakes and disc brakes), more and more large buses and trucks are equipped with eddy current retarder as auxiliary braking device. As early as 1903, the French engineer Steckel applied for the world's first patent of eddy current braking for automobiles according to the eddy current principle. 1936, French engineer Raoul Roland Raymond Sarazin developed the world's first eddy current retarder.
After the end of World War II, Telma S.A of France officially purchased another patent of eddy current retarder from Sarin, and successively introduced A series retarder installed on the transmission shaft and F series retarder installed on the gearbox and rear axle.
Retarder principle
Eddy current braking is based on the eddy current phenomenon discovered by French physicist Leon Foucault. The basic principle is to arrange magnets alternately according to N and S poles and keep a certain gap with metal conductors. When the magnet moves relative to the conductor, electromagnetic induction is generated, and a closed eddy current (eddy current) is generated in the conductor. The magnetic field generated by the eddy current deforms the main magnetic field, deflects the magnetic lines of force, and produces a tangential component force opposite to the direction of motion, that is, braking force. The direction of resistance can be determined by Fleming's left-hand rule. When eddy current flows in a conductor with a certain resistance, it converts electromagnetic energy into heat energy, which causes the conductor to heat up.
The main advantages of eddy current braking are no mechanical wear, and the braking force is stable in a large speed range, which is suitable for heavy vehicles, high-speed trains, lifting machinery and other occasions.