Railway FAQ & Glossary
Railway Market FAQ
Compliance & Certifications
What is EN 50155 and why does it matter for my railway power supply design?
EN 50155 is the CENELEC standard covering electronic equipment on rolling stock, including power supplies. Though European in origin, it's the standard railway power supplies worldwide are most commonly designed and tested to — addressing supply voltage variation, operating temperature, shock and vibration, EMC, and reliability.
If you're designing for rolling stock, EN 50155 compliance should be your starting point. Our Melcher-brand AC-DC and DC-DC converters are designed to meet the latest requirements, and our engineering team can help you select the right solution for your application.
What companion standards do I need to account for alongside EN 50155?
EN 50155 doesn't stand alone — you'll need to address several companion standards simultaneously:
- EN 45545-1/-2: Fire safety — materials, construction, and testing; hazard levels HL1 to HL3.
- EN 50121-3-2: EMC — conducted emissions and immunity for railway equipment.
- EN 61373: Shock and vibration — test severity by mounting category (body, bogie, or axle).
Navigating overlapping standards is one of the biggest challenges in railway design. Our Melcher products comply with EN 50155, EN 50121-3-2, and EN 45545 (HL1–HL3), and we can provide fire safety assessment test reports to support your system-level certification.
What fire safety certification does my railway power supply need?
EN 45545-2 specifies flammability, smoke density, and toxicity requirements across three hazard levels. HL3 is the most stringent, typically required for enclosed areas with limited escape routes. You'll need certification demonstrated through testing at a certified lab.
Our Melcher cassette converters are certified to EN 45545 for HL1 through HL3, and also comply with national fire standards DIN 5510-2 (Germany) and NFF 16-101 classification I3/F2 (France) — so you're covered regardless of where your rolling stock operates.
My project has deployments outside of Europe. What regional railway standards should I know about?
Several countries maintain their own standards with distinct input voltage ranges, environmental requirements, and fire safety classifications. Depending on your deployment geography, you may need to comply with:
- AREMA: USA/Canada
- RIA 12: UK
- NFF 01-510: France
- STM-E 001: Sweden
- GOST: Russia
Our railway products are designed for global compliance across EN 50155, AREMA, RIA 12, STM-E 001, and GOST. Reach out to our engineering team to confirm which regional certifications you'll need for your target markets.
Technical Specs
What battery voltages and input ranges does my power supply need to handle?
EN 50155 defines nominal DC battery voltages of 24, 28, 36, 48, 72, 96, and 110 V (24, 72, and 110 V recommended). Your supply must handle continuous operation at nominal ±25%/−30%, transients of ±40% for 0.1 s, and ride through voltage interruptions — the default class (S2) requires maintaining operation through complete interruptions up to 10 ms.
These ranges are significantly wider than standard commercial DC-DC inputs. Our converters offer ultra-wide input ranges (up to 10:1 ratio) covering all common railway battery voltages, with extended hold-up time options to meet S2 interruption requirements.
How do I choose the right operating temperature class?
The 2017 edition of EN 50155 defines six classes. OT3 (−25 °C to +70 °C) is the default for equipment in technical cabinets. OT4 extends the low end to −40 °C, while OT5/OT6 reach +85 °C for special applications. All equipment must also handle −40 °C to +85 °C for at least 10 minutes during start-up.
Match your temperature class to where the equipment will actually be mounted — not just where it's tested on the bench. Our Melcher cassette and chassis-mount converters start up at −40 °C with no derating to +70 °C, covering OT3/OT4. Talk to us if you need OT5/OT6.
How do shock and vibration requirements affect my power supply selection?
EN 61373:2010 defines three mounting categories — body-mounted (Category 1), bogie-mounted (Category 2), and axle-mounted (Category 3) — with increasing test severity. Category 2, Class B is the default. Your mounting location determines the required test level, so decide this early in your design.
Don't wait until qualification testing to discover your power supply can't handle the vibration profile. Our Melcher converters are built in rugged housings and undergo extensive EVT/DVT and HALT/HASS testing for railway mechanical environments.
What useful life should I be designing for?
EN 50155:2017 defines five life classes: L1 (5 years) through L4 (20 years) and LX (special). L4 — 20 years — is the default unless you and your customer agree otherwise. Get alignment on this early, as it influences component selection and design margins.
Our Melcher converters use fanless, convection-cooled designs and dip-varnished circuits built for the long haul. If you need custom extended-life configurations, our engineering team can help.
Product Fit & Use Cases
What power conversion options are available for my railway application?
We offer railway-qualified products from 4 W to 15,000 W under the Melcher brand, including DC-DC cassette converters (rack or chassis mount, inputs from 12–220 V nominal), DC-DC chassis-mount converters (60–1,000 W), PCB-mount DC-DC converters (wide inputs from 7–160 VDC), AC-DC subrack systems (up to 1,500 W with hot-swappable cassettes and true redundancy), and railway battery chargers. We also offer transformers, fuses, and integrated connector modules (ICMs) for rail systems.
Use our parametric search on belfuse.com to filter by input voltage, output, power level, and form factor — or contact us directly to talk through your application requirements.
What if I need something that isn't a standard off-the-shelf product?
We can modify standard Melcher designs to include features like extended hold-up time, extended useful life, inverse voltage protection, output voltage adjustment, monitoring relays, and shutdown inputs. We also provide regulatory assistance to help you navigate multiple simultaneous standards.
Whether you need a small modification or a fully custom solution, reach out to our sales engineering team. We'll scope the right approach and include regulatory support so you're not solving compliance on your own.
Railway Market Glossary
AREMA
American Railway Engineering and Maintenance-of-Way Association. The US/Canadian body that publishes recommended practices for railway engineering, including electrical equipment standards.
CENELEC
European Committee for Electrotechnical Standardization. The organization responsible for developing EN-series standards, including EN 50155.
DIN 5510-2
German national standard for fire protection on railway vehicles, covering material flammability, smoke density, and toxicity.
EMC
Electromagnetic Compatibility. The ability of equipment to operate without generating interference that affects nearby devices, and to function correctly in the presence of external electromagnetic disturbances.
EN 45545-1/-2
European fire safety standard for railway vehicles. Specifies material, construction, and testing requirements across three hazard levels (HL1–HL3).
EN 50121-3-2
European standard for electromagnetic compatibility of railway equipment. Defines conducted emissions limits and immunity test levels by port type.
EN 50155
European standard for electronic equipment used on rolling stock. The primary standard governing power supply design for railway applications, covering supply voltage, temperature, shock/vibration, EMC, and reliability.
EN 50163:2014
European standard covering voltage requirements for AC supply from overhead lines or third rail.
EN 50533:2011
European standard covering AC power supplied by auxiliary converters on rolling stock.
EN 61373
European standard for shock and vibration testing of electronic equipment on rolling stock. Defines three mounting categories (body, bogie, axle) with increasing test severity.
EVT/DVT
Engineering Validation Testing / Design Validation Testing. Rigorous test programs used to verify that a product meets its design specifications and performs reliably under expected operating conditions.
GOST
Russian state standards system. Includes railway equipment standards applicable in Russia and CIS countries.
HALT/HASS
Highly Accelerated Life Testing / Highly Accelerated Stress Screening. Test methods that apply extreme stress (temperature, vibration) to identify design weaknesses and screen for manufacturing defects.
HL1 / HL2 / HL3
Hazard Levels defined in EN 45545-2. HL1 is the least stringent; HL3 is the most stringent, typically required for enclosed areas with limited escape routes.
ICM
Integrated Connector Module. A component that combines magnetic isolation and RJ45 connectivity in a single package, used for Ethernet connections in railway systems.
Melcher™
Bel's brand for high-performance, ruggedized power converters designed for railway, industrial, and harsh-environment applications. Founded in 1973.
NFF 01-510
French national standard for electronic equipment on rolling stock, with distinct input voltage specifications from EN 50155.
NFF 16-101
French national fire safety standard for railway rolling stock materials. Classification I3/F2 indicates compliance with flammability and smoke requirements.
NFPA 130
US standard for fire protection in fixed guideway transit and passenger rail systems.
OT1–OT6
Operating Temperature classes defined in EN 50155:2017. Range from OT1 (−25 °C to +55 °C) to OT6 (−40 °C to +85 °C). OT3 is the default.
RIA 12
Legacy British standard defining input voltage specifications for electronic equipment on railway rolling stock.
S1 / S2 / S3
Supply voltage interruption classes defined in EN 50155:2021. S2 (default) requires maintaining normal operation through complete interruptions up to 10 ms.
STM-E 001
Swedish standard for electronic equipment on railway rolling stock.
L1–L4 / LX
Useful life classes defined in EN 50155:2017. Range from L1 (5 years) to L4 (20 years, default). LX covers special requirements agreed between manufacturer and end user.
Vn
Nominal voltage. The designated battery voltage of a railway DC supply system (e.g., 24, 72, or 110 V), used as the reference point for calculating continuous, transient, and overvoltage limits in EN 50155.
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