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Railway applications present many potential uses for DC-DC converters. Electronic systems onboard modern trains for both critical systems or passenger comfort and convenience need DC-DC converters to lower the main DC battery voltage to their individual input requirements. But, all these systems in close proximity create unwanted signals that affect the safe operation of the train. They also encounter harsh environmental conditions aboard the train including shock, vibration and temperature and humidity extremes.


What is EN50155?

EN50155 is an international standard pertaining to the conditions that can impact railway operations and safety such as harsh environments or the interacting signals between multiple electrical/electronic systems. It encompasses several existing standards, such as EN50121-3-2 for EMC (electromagnetic compatibility) and EN61373 for shock and vibration. In order to attain EN50155 approval, power supplies undergo stringent testing for a host of challenging conditions. Some of the most important parameters pertaining to power supplies include:

  • Input voltage. Since trains present a diversity of bus voltages, EN50155 outlines nominal input voltages of 24, 48, 72, 96 and 110V. EN50155 sets limits for fluctuations of the rated voltage and establishes short-term deviations. The supplies must also provide an output during power interruptions.
  • EMC. With so many electronic systems populating railway vehicles, EN50121-3-2 sets strict limits to radiated emissions and ESD levels, including events like surges and fast transient bursts.
  • Shock and vibration. Not surprisingly, components inside moving rail stock will encounter frequent vibration and mechanical stresses. EN50155 establishes minimum vibration and shock requirements depending on where the device is mounted in the railway vehicle: body mounted, bogie or "truck" mounted or axle mounted.
  • Temperature and humidity. The standard provides different classes of operating temperatures for power supplies, depending on the environment. They must operate at 85 percent efficiency to reduce dissipated power that can otherwise be lost as heat, and they are required to withstand a 15-degree overtemperature at startup for 10 minutes. EN50155 also establishes humidity requirements.


Look for EN50155 Compliance

Designers that choose a DC-DC converter with EN50155 approval can be sure it will perform reliably aboard rolling stock. One example of a DC-DC converter designed especially for railway applications is Polytron Devices’ HWB Series DC-DC converters. These half-brick power supplies operate from 9-36V, 8.5-36V, 16.5-75V and 43-160V DC with no minimum load requirement, and they boast a high efficiency of up to 91 percent. The series’ EN 50155 approval also means it satisfies EN50121-3-2 (with external filter) and EN61373 for shock and vibration. Additional approvals include the EN61000-4-2, -3, -4, -5 and -6 EMC standards and UL/EN/IEC 60950-1 for safety. HWB Series converter safeguards include overvoltage, overtemperature and short-circuit protections plus heat sink options.


Conclusion

When selecting DC-DC converters for railway applications, look for devices that carry EN50155 certification. HWB Series DC-DC converters have been tested and approved to EN50155 so you can be sure they can both manage EMC and perform in the challenging conditions aboard rolling stock. Polytron Devices can furnish the applicable EN50155 test reports upon request.


For more information about Polytron Devices’ HWB Series DC-DC converters for railway applications, visit www.polytrondevices.com.