Designating a product as rail-approved means that the product has been tested according to all relevant standards for rail vehicles. The relevant standards differ between component types. For DC/DC converters, the relevant standards are:
EN 50155 – Railway applications – Electronic equipment for rail vehicles
EN 50121-3-2 – Railway applications – Electromagnetic Compatibility (EMC) – Part 3-2: Vehicles – Apparatus.
EN 61373 – Railway applications – Shock and vibration requirements for vehicle equipment
EN 45545-2 – Fire safety of railway vehicles – Part 2: Fire safety requirements for materials and components