A magnetic brake (abbreviated Mg) is a brake for rail vehicles. It consists of iron sanding pads with built-in solenoid. Wherein current flow through the solenoid of the pressure pad is drawn against the rail. This mainly results in a braking friction force.
In addition, an eddy current occurs to the induction rail, generates a force opposing the movement. Since the friction forces decrease with decreasing speed and the eddy current forces, the brake acts compared to a wheel with metallic brake pads in the entire range of relatively linear.
Use in standard-gauge railways
In full paths, the magnetic track brakes in the resting state are relatively far away from the rail; the German railway for example, prescribes a minimum distance of 5.5 cm. Therefore, the brake shoes must be lowered pneumatically upon activation; only to the last millimeter pulls the brake shoe itself magnetically to the rail. Magnetic rail brakes in the event of a catenary failure to operate safely. The braking system is therefore interpreted as meaning that in the event of a power failure at any time a supply from the batteries of the vehicle is guaranteed.
According to the brake boards of the Deutsche Bahn are for driving in a Vorsignalabstand of 1000 meters at point-like train control ( PZB )
- Up to 140 km / h 146 braking percentage
- Up to 160 km / h 208 braking percentage
Necessary. More than 170 brake mass percentages are not approved for use in international traffic by way of value-dependent wheel - stopping (eg shoe brake, disc brake or electric motor brake). At still higher stress is a risk of excessive response of the WSP.
The magnetic brake acts directly on the rail and is the coefficient of friction between wheel and rail independently. It is therefore used in Germany for all coaches and trainsets that are out PZB approved for speeds over 140 km / h. In long-distance trains the magnetic rail brake is off at speeds below 50 km / h due to the high braking forces.
Only the approved for 330 km / h ICE 3 is the only fast-moving series-production of the Deutsche Bahn on eddy current instead of magnetic track brakes (as of October 2006). This braking system is wear-free and more powerful than a magnetic rail brake.
Use in trams
Trams must be fitted in Germany since 1st January 1960 generally with magnetic track brakes to deliver in the event of emergency braking the prescribed delay of up to 2.73 m/s2, so that the necessary road traffic short braking distances remain guaranteed even with slippery rails. Not the Passenger Transportation serving tram vehicles are exempt from this requirement, but it may only run at a reduced speed.
Unlike full tracks the magnetic track brakes for trams are very close mounted on the rail ( 0.8 to 1.2 cm) and therefore need not usually pneumatic lowering unit.
- Martin Karr: multi-system concepts of railways in Europe. Presented as Vertieferarbeit at the Institute of Road and Railway Engineering (Department of Railway Engineering ), University of Karlsruhe ( TH) with Prof. Dr. -Ing. Hohnecker. Karlsruhe 1998
- Railway operation
- A rail vehicle brake