Electropneumatic brake

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The electropneumatic brake (ep or EP brake) is an electropneumatically controlled automatic compressed air brake on railways .

Brake address on a car with an electro-pneumatic brake
Nine-pin plug of the control cable for UIC-ep brake

The ep brake enables all vehicles to be braked or released simultaneously, regardless of the length of the train. That is with the pure air brake because of the 280 m / s limited penetration speed not possible. The ep brake actuates all braking devices electrically at the same time and enables even braking with the lowest longitudinal pressure forces in the train. The ep brake is particularly suitable for passenger cars that already use electrical energy and are equipped with a main air reservoir line to supply non-brake consumers such as door and toilet controls or air suspension systems.

The locomotive is equipped with a control unit. The individual cars are equipped with electropneumatic valves. The electrical control commands are transmitted and monitored via a control line ( ep line ). The ep brakes are divided into two versions:

Indirectly acting ep brake

In passenger trains of long-distance transport , the indirectly acting dual-line ep-brake has prevailed. The driver's brake valve is used to actuate the control unit on the locomotive or control vehicle , which issues an electrical brake or release command when the pressure in the main air line is reduced or increased. This brake works in parallel with the automatic compressed air brake. Each vehicle has two solenoid valves: a brake valve and a release valve. The brake valve allows air to flow out of the main air line. The release valve connects the main air reservoir line to the main air line and increases its pressure so that the brake is released. The indirect ep brake thus acts on the automatic compressed air brake of all vehicles coupled to the main air line. If the electro-pneumatic control fails, the brake is controlled purely pneumatically via the main air line.

However, the indirectly acting ep brake was only used with the demand for passenger emergency brake bridging systems (NBÜ), with which a stop at unfavorable points can be prevented. Two different systems are used:

  • The UIC-ep brake according to leaflet 541-5 uses the UIC control line to transmit the brake and release signals. It is therefore also suitable for vehicles without their own power supply such as B. freight cars can be used. Monitoring the control line for malfunctions and any train separation controls the current availability.
  • the DB-ep brake, which is used in long-distance passenger coaches operated by Deutsche Bahn , uses the information and control cable or the loudspeaker cable for signaling. The switching energy for the solenoid valves is taken from the power supply of the car. The functionality of the DB-ep brake is not monitored.

The ep brake has not caught on with freight trains . On trains with an automatic UIC central buffer coupling and large coupling play, the use of the classic compressed air brake caused violent reactions in the train, which led to derailments . The ep brake turned out to be the most effective way of avoiding them. Since the automatic coupling was not introduced, the ep brake was also dispensed with in freight trains.

Direct acting ep brake

Direct-acting ep brakes are mainly used in local multiple units. A control unit on the locomotive or control car is combined with the driver's brake valve or the relevant control element. The control unit issues a brake or release command that is proportional to the desired braking effect. There is an electropneumatic valve on every vehicle in the train, which regulates the pressure in the brake cylinders depending on the command in the electrical control line.

An essential condition of the direct ep brake is that the automatic braking effect is guaranteed in the event of a train separation. For this purpose, either an additional, indirectly acting compressed air brake is installed, or the train is monitored with an elaborate electrical safety loop.

Data bus or train bus brake

The indirect and direct ep brakes can be controlled via a data bus . This means that numerous additional functions such as diagnostics , remote control or continuous blending can be easily carried out.

Such brakes essentially consist of a traction vehicle control computer, the train bus based on wire or radio, and the vehicle equipment with electronics and pneumatics. For multiple units and passenger trains, the Wire Train Bus (WTB) is used as the train bus , which is designed for train lengths of up to approx. 860 meters. Within a vehicle, a vehicle bus, e.g. B. the Multifunction Vehicle Bus (MVB) communicated. The WTB is not suitable for freight trains, especially since other requirements are in the foreground. For freight trains, the possible bus length (at least 1000 meters) and the costs are decisive.

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