High-speed rail EMUs use composite braking. That is, at least two methods are used for braking.
National high-speed rails all use dispersed power electric multiple units. Therefore, during the normal braking process, regenerative braking is given priority, that is, the electric motor is reversed and turned into a generator, which turns the electric motor into a generator. The kinetic energy of the EMU is converted into electrical energy, which is sent to the catenary for use by other EMUs in adjacent sections. However, the electrical energy generated by the EMU through regenerative braking cannot be fed back into the external national grid because it contains a large number of harmonics. Regenerative braking is also a relatively environmentally friendly and green braking method.
When the speedof the EMU is very weak and it is about to stop, the effect of regenerative braking is relatively small, so it will be replaced by disc braking, or when the catenary fails or If there is a power outage, emergency braking must be initiated. When traveling, disc brakes are used. It works the same way as your car's brake rotors. Two to four brake discs are placed on the axle, or part of the wheels at both ends are used as brake discs. The calipers hold the brake rotors and generate friction and heat, thereby converting the kinetic energy of the EMU into thermal energy and dissipating it. to achieve the deceleration objective. Disc brakes are also called safety brakes, which are designed to be used normally even in the event of a failure of the external contact network and in the absence of power supply, thus ensuringthat the EMU can safely shut down.
The national high-speed test vehicle CRH380AM also uses wind resistance braking. That is, when braking, the wind resistance plate is raised at the end of the train, thereby increasing the air resistance of the EMU and achieving accelerated deceleration the purpose of.
The German EMU ICE3 also uses eddy current braking, that is, when braking, a set of electromagnets is lowered to a distance of less than 10 centimeters from the rails, then energized, the electromagnets are in contact with the rails. Eddy currents are generated to generate heat, thereby converting kinetic energy into thermal energy and dissipating it to achieve the goal of deceleration. The advantage of this braking method is that it is not affected by increasing speed at high speeds and can maintain itself. greater braking forcelifting at high speed. The downside is that the track overheats due to high heat generation, which requires time to dissipate and cool down.
Japanese Shinkansen, like the 500 series, still use disc eddy current brakes. Unlike the German ICE3, an eddy current disk is placed directly under the car to directly convert kinetic energy into thermal energy. achieve the goal of slowing down.
The French TGV-A uses an alternating current synchronous motor, the safety brake therefore uses resistance braking. In other words, when the catenary fails, the battery is directly used to reverse the motor and transform it into a generator. the electrical energy generated is consumed by heating through the braking resistor of the motor vehicle.