The magnetic rail brake (Mg brake) is a technology used to stop rail cars. It works by creating a powerful magnetic field between electromagnets mounted under the carriage and the rails. This magnetic field generates an electromagnetic force that counteracts the carriage’s motion, thus slowing and stopping it.
Device and Working Principle Use Principle and Functionality Suspension Pole Shoes Actuating Cylinders Friction Material Modular Magnetic Rail Control (MMBC) Advantages of Mg Brakes Disadvantages of Mg Brakes
Device and principle of operation
It consists of brake magnets, pole shoes, suspension and rail rod. When current flows through the magnetic coil, the magnet is attracted to the rail, which presses the pole shoes against the rail, thus slowing the vehicle.
Whereas disc brakes or shoe brakes depend on the frictional connection between the wheel and the rail, the magnetic rail brake acts directly on the rail. Therefore, its braking effect is not limited by the wheel-rail contact. Thus, environmental factors such as moisture or rail contamination have less influence on the braking force.
Usage
Magnetic rail brakes are used on rail vehicles in addition to the basic, effective wheel braking systems. As an additional braking system, they help to comply with the prescribed braking distances of rail vehicles.
Since magnetic rail brakes always operate unregulated and at maximum braking force, they are only used as safety and emergency brakes. They can be used at speeds up to 270-280 km/h. With the use of special friction materials, they can be used up to speeds of 350 km/h.
Thanks to their cleaning effect, magnetic rail brakes increase the coefficient of adhesion between the following wheels and the rail during the braking process. This further leads to the improvement of wheel-efficient braking systems.
In general, magnetic rail brakes are distinguished between solid and hinged magnets.
Principle and functionality
The main component of a magnetic rail brake is the brake magnet. Following the principle of the electromagnet, it consists of a coil wound around an iron core, which is surrounded by horseshoe magnets.
A direct current flows through this magnetic coil, generating a magnetic field. This causes a force of attraction between the brake magnet with its attached pole shoes and the rail. The shoes of the posts are pressed against the rail and the resulting friction converts the kinetic energy of the movement into heat (dissipation) until the kinetic energy is used up or the brake is deactivated.
Magnetic rail brakes must also operate safely in the event of contact line failure. Therefore, the braking system must be designed in such a way that in the event of a power failure, power from the car’s batteries is guaranteed at all times.
Suspension
The suspension is responsible for holding the disconnected magnet above the rail. In case of braking, the magnet is automatically attracted to the rails against the effect of the suspension springs. After tripping, the suspension springs pull the magnet back to the ready position.
Pole shoes
The pole shoes are located on the underside of the brake magnet. There is a non-magnetic strip between the two pole shoes to ensure that no magnetic short circuit will occur.
The friction material of rail shoes can be made of different materials, each of which determines the service life and braking performance of the rail shoes.
Actuating cylinders
The drive cylinders are located on top of the brake square. They are responsible for lowering the brake frame onto the rails and raising it again.
Built-in springs hold the brake frame in a high position when the brakes are not actuated. When the brakes are applied, the brake frame is pneumatically lowered onto the rails against the force of the springs. The compressed air supply required for this is provided by a separate compressed air tank. This ensures that the braking system continues to work even if the wagon’s brake pipe fails. When the brakes are released, the springs in the actuating cylinders raise the brake frame back to the high position
Friction material
The pole shoes in magnetic rail brakes can be made of different materials. They differ mainly in their magnetic properties, braking force coefficient and wear.
Modular Magnetic Rail Control (MMBC)
Knorr-Bremse electromagnetic rail brakes are controlled by the Modular Magnetic Rail Control (MMBC) system. Within the group, Knorr-Bremse is responsible for the development of this fully electronic control system.
The key advantage of electromagnetic rail brakes in the daily operation of rail vehicles is that the braking force is applied directly to the track and is not affected by the coefficient of friction between wheel and rail. For this reason, they are mainly used in LRV braking systems – the fact that LRVs share roads and transit corridors with many other road users means that track conditions can be much more variable than in the case of other forms of rail. transport.
Advantages of Mg brakes
Shorter braking distance: Mg brakes can shorten the braking distance by 2-3 times compared to traditional friction brakes. This is especially important on high-speed trains, where it is essential to stop quickly and safely.
Reduced wear: Mg brakes do not wear the wheels and rails in the same way as friction brakes. This can lead to significant savings in maintenance costs in the long run.
Lower noise level: Mg brakes are much quieter than friction brakes, which can reduce noise pollution, especially in urban areas.
More environmentally friendly: Mg brakes do not emit harmful emissions or dust like friction brakes.
Disadvantages of Mg brakes
- High initial investment: Mg brakes are more expensive to install than traditional friction brakes.
- Limited compatibility: Mg brakes cannot be fitted to all railcar types.
- Electrical power required: Mg brakes require electrical power to operate, which can be a problem in some areas with limited power supply.
Despite these drawbacks, Mg brakes are considered a promising technology with the potential to revolutionize rail transport. They are already used in some high-speed trains and are expected to become more widespread in the future.
In addition to the information above, here are some more interesting facts about Mg brakes:
The first Mg brake was developed in Germany.
The first commercially used Mg brake wagon was put into service in Japan.
Mg brakes are currently used in railway systems in Japan, China, South Korea and Germany.