Relays for safe braking control

Relays for safe braking control

Reliable switching in railway technology

Rail relays ensure electrical isolation between sensor and controller.

Your advantages

  • Optimum relay operation, thanks to wide-range electronics
  • Extended temperature and input voltage range up to TX class
  • Robust, plug-in relay: splash-proof (RTIII protection) and resistant to dust and humidity
  • Shock and vibration resistant, according to DIN EN 50155
  • Safe isolation according to DIN EN 50178 between coil and contact


The braking control is one of the safety-related systems of a train. Depending on the application, intelligent additional functions can be integrated into the braking control, such as load-dependent braking or emergency braking equipment. To this end, in the event of emergency braking, disc brakes are supported by additional braking systems.


Rail relays from Phoenix Contact  

Rail relays from Phoenix Contact

Special relay modules from Phoenix Contact are used to control auxiliary braking systems. In order to activate the auxiliary brake, for example a magnet rail brake, several requirements must be met first: rotary transducers on the carriage axle continuously detect the travel speed and evaluate this.

From a defined speed, a signal is sent to the rail relay. The electromechanical relay switches through and forwards the 24 V DC signal to the central controller. Furthermore, the relay ensures electrical isolation between the field sensor and the controller.

The electrical interference signals, or transients, which are common in rail vehicles, are filtered out. As such, the central controller is protected from surge voltage and overcurrent and all safety-related functions of the system can run without errors.

Hard gold-plated contacts for reliable contact

The reliable switching of the rail relays is ensured, thanks to hard gold plated contacts. The plating prevents oxidic contamination layers forming on the contacts. However, this is just one of the features of a rail relay, as gold contacts are also used in other industrial applications where small loads and signals have to be switched.

When it comes to special relays, the PLC.../21RW module must initially conform to the EN 50155 railway standard. Electromechanical relays usually have to conform to EN 61810.

Extreme temperatures are not uncommon

The rail relays are equipped with an extended temperature and input voltage range. This is one of the requirements of EN 50155, as the high demands placed on the ambient temperature play an important role in practical operation.

Control cabinets for the braking control are installed in the rail cars below passenger level in the underfloor vehicle body. The vehicle body is made of steel and is not heat-insulated. Depending on the time of year and location where the train is used, the temperatures inside the vehicle body can differ greatly from ambient temperatures encountered in industrial applications.

In extreme cases, an input voltage up to 125 percent of the nominal voltage can occur simultaneously as an increased ambient temperature of up to +70°C. Due to the high voltage, more current flows through the relay module, which results in increased self-heating. Faced with a high ambient temperature simultaneously, a normal relay module would quickly fail.

Other fields of application for rail relays

rail relays from Phoenix Contact are used in an extremely wide range of applications in rail vehicles, for example in the vacuum-operated toilet controllers. The relay, as the link between the field level and the central controller, provides electrical isolation.

The relays developed specially for the railway industry, with their narrow modular design of just 6.2 mm, can be plugged in flexibly and are therefore easy to maintain.


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