Magnetics for Railway Rolling Stock: EN 50155, EN 45545-2 and EN 61373

Rail Standards Change the Component, Not Just the Paperwork

Magnetics for rolling stock — auxiliary converters, traction drive isolation, battery chargers, door and HVAC inverters — are specified against a different standard set than industrial parts. EN 50155 governs electronics on rail vehicles, EN 45545-2 governs fire behaviour of materials, and EN 61373 governs vibration and shock. Together they eliminate several constructions that would be perfectly acceptable in a factory.

The practical consequence: a magnetic component that passes on the bench can fail rail qualification for reasons that have nothing to do with its electrical design — a bobbin resin that fails smoke toxicity, a potting compound that cracks under vibration, or a thermal design that assumed 25 °C ambient instead of a sealed cabinet at 70 °C.

The Three Standards That Matter

Rail requirements that directly shape a magnetic component
Standard	What it requires	Design impact
EN 50155	Ambient classes (OT1–OT4, ST1–ST2), supply voltage ranges, temperature cycling	Class OT4 (-40 to +70 °C) is common; hotspot margin shrinks
EN 45545-2	Fire hazard level (HL1–HL3) by material and application	Bobbin, potting, tape and sleeving need R22/R23/R24 compliance data
EN 61373	Random vibration and shock by mounting location (body, bogie, axle)	Clamping, potting and lead-wire strain relief must be designed, not assumed

EN 45545-2 is the one buyers underestimate. It is not a burning test on the finished part; it is a material-level hazard assessment where each plastic in the construction contributes to smoke density and toxicity. A standard PET bobbin with no rail-grade documentation can block approval even if the electrical design is perfect.

Thermal Design in a Sealed Cabinet

Rail auxiliary cabinets are sealed and often passively cooled, with internal ambient 60–70 °C. A 5 kVA transformer that runs at 40 K rise on the bench may see 100 K rise inside the cabinet, which pushes Class H insulation to its limit and cuts life. Two design responses:

Specify the rise at the actual cabinet ambient, and require the supplier’s hotspot location and thermal resistance, not a generic “class H” claim.
Prefer conduction-cooled construction — a potted or thermally bonded core path to the mounting surface — over open-frame parts that rely on air movement that does not exist in the cabinet.

Vibration and Connection Integrity

EN 61373 vibration at body-mounted levels is modest, but at bogie or axle level it is severe. The failure mode in magnetic components is rarely the core: it is the winding moving against the barrier, enamel abrasion, and lead wires fatiguing at the solder joint. Potting plus a defined lead-wire support, with a pull and bend test in the qualification plan, prevents the majority of these failures.

Terminations should be rated for the vibration class, and the drawing should state the clamping force and the mounting bolt torque, because a core that shifts under vibration changes inductance and can open a gap that was never designed.

What to Put in the Rail RFQ

EN 50155 ambient class and supply voltage range, including the dips and surges the converter must ride through.
EN 45545-2 hazard level and the material list you need documented.
EN 61373 mounting location category and the vibration test level.
Required documents: fire test reports per material, vibration test report, thermal analysis at cabinet ambient.
Expected service life and maintenance interval — rail programs often specify 30 years with defined refurbishment.