EN 50155: The Essential Standard for Power Supply Design in Railway Applications

ENSURING SAFETY IN MODERN RAIL SYSTEMS

Standards are essential for the design and development of safe and reliable power supply products, especially for transportation systems such as railways. Technical standards address performance, design methodology, verification, implementation, safety, and risk assessment within the context of how they’re going to be used in the real world.

Power distribution systems on trains, no matter their purpose, must be safe and reliable, which means complying with a host of standards, EN 50155 prominent among them. EN 50155 is a European standard that covers electronic equipment used on rolling stock for railway applications, including power supplies. Though the standard was developed by the European Committee for Electrotechnical Standardization (CENELEC), it addresses the global rail market, and is the standard that power supplies for rail applications are often designed and tested to.

Trains, including commuter, light rail, freight, and high-speed are already quite popular in places like Europe and Japan, and other regions are increasingly turning to rail to move people and goods more efficiently. EN 50155 has become increasingly important as trains have become more technically advanced from an engineering and passenger experience perspective.

Onboard Wi-Fi, sophisticated climate systems, and complex control and management systems are all placing new demands on electrical systems. This has led to several revisions of EN 50155 as it is continuously updated to assure that standards are keeping up with the growing complexity.

THE PRIMARY STANDARD

EN 50155 covers all of the electronic equipment used for control, regulation, protection, diagnostics, and energy supply in rolling stock applications. The requirements placed on this equipment includes operating conditions, product design and documentation, testing, integration, and software.

Power supplies and converters, which are needed to provide clean and stable power to all of electronics found in modern rail applications, fall within the scope of the standard. The key concerns of power supplies in the rail market include supply voltage variation, operating temperature, shock and vibrations, electromagnetic compatibility, and reliability.

REFERENCED STANDARDS

Standards don’t exist in proverbial silos, and EN 50155 is no different. It references many other standards that often deal with more specific issues. Some of those standards that especially apply to power supply design include:

THE EVOLUTION OF EN 50155

As power supply technology has evolved, railways have modernized, and safety requirements have changed, EN 50155 has undergone several revisions since its first publication in 1995 to keep pace.

The first revision came in 2001 and included new requirements for safety management. It also clarified and strengthened existing requirements.

A big update occurred in 2007 and included the addition of three test categories:

Testing provisions in the update require that the user shall identify any tests subject to agreement at the time of tendering, while the manufacturer is required to provide a test plan listing all the tests to be performed and their specifications. The equipment is not allowed to malfunction or produce a performance which is outside its specification, as per the 2007 update, which also advises only those tests which are necessary must be carried out as some tests may be costly.

Notable changes in 2017 include the addition of a new reliability test, a rapid temperature variation test, while definitions and illustrations of test conditions were further clarified to allow for more accurate experimentation.

The most notable update in 2017 was a move to six operating temperature classes, shown in Table 1. The default level is OT3. This update also added responsibility with equipment manufacturers and end-users to define operating temperatures for equipment and determine relevant constraints.

There is also more flexibility around the length of useful life of all equipment – previously it was 20 years, but as of 2017 there are five classes, beginning with five years. However, level 4 is the default, unless otherwise specified.

In 2021, a third performance criterion was added, outlining allowable degradation in the event of a test or environmental disturbance, and stipulating the loss of significant stored data is not permitted. EN 50155:2021 also outlines which type of battery voltage supply systems are permitted.

EN 50155 AND ITS RELEVANCE TO POWER SUPPLIES

Power supplies for any type of equipment always influence the design and development of products they’re going into. Standards such as EN 50155 are especially relevant where there are not only stringent performance requirements, but also public safety concerns.

The EN 50155 standard applies to many different aspects of electronic equipment, including installation, control, regulation, and protection. All this equipment is integrated into complex systems, operating in complex real-world environments.

There are five areas that are crucial when designing power supplies for railway rolling stock equipment.

These five main areas of EN50155 reflect the real-world environment within which railway rolling stock must operate while accommodating for the utmost safety of people, whether it’s passengers, crew or anyone that comes close to where the train is traveling.

STANDARDS STEER BEL POWER SUPPLIES FOR RAILWAY APPLICATION

Power supplies are critical elements in rail system design and proper selection is fundamental to rail safety. That multiple standards apply simultaneously makes the selection more complex than it otherwise would be, so consulting an expert vendor is recommended, one with a long history of designing and developing power supplies in rolling stock for railway applications, as well as harsh environments.

Bel, through the Melcher brand, offers a wide breadth of AC-DC power supplies and DC-DC converters designed to meet the latest requirements of the EN 50155 standard. Melcher has a long history of designing and manufacturing rugged and reliable power supplies for railway applications and ensuring that products keep pace with the ever-changing safety requirements. The experts and engineers at Melcher can assist with finding the optimal EN 50155 compliant power supply solution for your railway applications.

Bel can create a custom versions of our many power supply designs to meet specific requirements by easily modifying standard designs to include features such as extended hold-up, long life, and inverse volt protection.