What Is EN 50121-3-2?

EN 50121-3-2 is the European standard for the electromagnetic compatibility (EMC) of electrical and electronic apparatus installed on railway rolling stock. Its full title is Railway applications – Electromagnetic compatibility – Part 3-2: Rolling stock – Apparatus, and its international counterpart is IEC 62236-3-2.

A train is full of high-power electrical systems, from traction motors and converters to signalling and train control, and electronics on board must coexist with them. EN 50121-3-2 sets the emission limits and immunity tests for apparatus installed on rolling stock, so that a computer, display or camera neither disrupts other systems nor is disrupted by them. It is commonly listed alongside EN 50155 on railway computer datasheets.

EN 50121 is a family of standards, each covering one part of the railway. Part 3-2 is the one that applies to a computer or other device fitted to a train. The current edition of Part 3-2 dates from 2016, with a later amendment, so the edition on a test report matters.

EN 50121-3-2 calls on the general EN 61000-4 test methods, with levels set for the railway environment. Levels depend on the port being tested and the edition of the standard, so the values below are typical rather than complete.

Each immunity test also has a performance criterion: whether the equipment must carry on working normally during the test, may degrade and recover by itself, or may need a reset. Railway buyers usually specify which criterion applies to each function.

EMC compliance matters as much as temperature and vibration on a train. EN 50155 is the main standard for electronic equipment on rolling stock, covering power supply variations, temperature, humidity and construction. Rather than repeat the EMC rules, it refers to EN 50121-3-2 for them, and to IEC 61373 for shock and vibration. That is why the three usually appear together on a railway computer datasheet. Fire behaviour of materials is covered separately by EN 45545-2, which railway buyers often ask for alongside the three.

Our EN 50155 summary covers the main rolling stock standard in more detail.

For a computer, meeting EN 50121-3-2 comes down to design rather than a single component. The features below are the ones that most affect the test results.

When you read a datasheet, check whether it says the product is compliant with EN 50121-3-2 or tested to it, which edition is cited, and whether a test report is available. Ask which ports were tested and which performance criterion each function met: a computer that resets during a surge test may still comply, but only for functions where a brief restart is acceptable. For safety-related or passenger information systems, look for the criterion that requires uninterrupted operation. Approval of the whole vehicle still depends on how the equipment is installed, so cabling and earthing on the train matter as much as the computer itself.

Our railway computers list their approvals, and our railway panel PCs cover driver and passenger displays. Our track inspection case study shows railway computers in service.

We supply railway computers and displays with the EN 50155, EN 50121-3-2 and IEC 61373 documentation for each model, and configure the system, power input and connectors to suit the vehicle as standard.