08-16-2017, 09:44 PM
vehicle retarder braking system seminar abstract
A retarder is a device used to augment or replace some of the functions of primary friction-based braking systems, usually on heavy vehicles. Retarders serve to slow vehicles, or maintain a steady speed on declines, and help prevent the vehicle from "running away" by accelerating down the decline. They are not usually capable of bringing vehicles to a standstill, as their effectiveness diminishes as vehicle speed lowers. They are usually used as an additional "assistance" to slow vehicles, with the final braking done by a conventional friction braking system. As the friction brake will be used less, particularly at higher speeds, their service life is increased.
Retarders are not restricted to road motor vehicles, but may also be used in railway systems. The British prototype Advanced Passenger Train (APT) used hydraulic retarders to allow the high-speed train to stop in the same distance as standard lower speed trains, as a pure friction-based system was not viable.
Electric retarders use electromagnetic induction to provide a retardation force. An electric retardation unit can be placed on an axle, transmission, or driveline and consists of a rotor attached to the axle, transmission, or driveline and a stator securely attached to the vehicle chassis. There are no contact surfaces between the rotor and stator, and no working fluid. When retardation is required, the electrical windings in the stator receive power from the vehicle battery, producing a magnetic field through which the rotor moves. This induces eddy currents in the rotor, which produces an opposing magnetic field to the stator. The opposing magnetic fields slows the rotor, and hence the axle, transmission or driveshaft to which it is attached. The rotor incorporates internal vanes (like a ventilated brake disk) to provide its own air cooling, so no load is placed on the vehicle's engine cooling system. The operation of the system is extremely quiet.
Retarder is an external brake frequently used in trucks. The purpose of the retarder is to assist in stopping the vehicle, controlling vehicle downhill speed on a steep grade, extending the life of the vehicle service brakes, and enhancing vehicle control. There are several retarder technologies currently available. Two major kinds are Hydraulic retarders and Electromagnetic retarders.