A retarder serves as an auxiliary device to the braking system. The vehicle retarder operates by energizing the excitation coil of the stator assembly through a control circuit, generating a magnetic field. The rotor assembly, rotating at high speed with the vehicle's drivetrain, cuts through the magnetic lines, creating a reverse torque that decelerates the vehicle. Simply put, when a vehicle needs to slow down or descend a long slope, engaging the retarder allows for smooth deceleration, avoiding the wear and heat generated by using the brakes. Additional information on retarders: Depending on their working principles, vehicle retarders can be categorized into engine retarders and hydraulic retarders. Engine retarder classification: Engine exhaust braking: An exhaust throttle valve is installed between the exhaust manifold and the muffler. By throttling the exhaust, the engine acts as an air compressor driven by the vehicle during the exhaust stroke. The increased exhaust backpressure enhances the negative work performed during the exhaust stroke. When the force difference acting on both sides of the exhaust valve (due to exhaust backpressure and cylinder pressure) exceeds the exhaust valve spring pressure, the exhaust valve floats (opens) independently of the camshaft control. The compressed air escapes through the intake valve during the valve overlap period, reducing the work done by expansion during the intake stroke. Hydraulic retarder: By operating a control valve, pressure is applied to the oil reservoir, filling the working chamber between the rotor and stator with working fluid. As the rotor rotates, it exerts a torque on the stator through the working fluid, and the stator's reverse torque becomes the braking torque for the rotor. The magnitude of this torque depends on the amount and pressure of the working fluid in the chamber (determined by the control valve's preset braking intensity level) and the rotor's speed. The vehicle's kinetic energy is converted into heat through the friction of the working fluid and its impact on the stator, raising the temperature of the working fluid.
