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RAIL Condition
Nominal Voltage Rated Voltage Continuous Voltage Transient voltage Extended Overvoltage DC Ripple Factor
Limit
Vn Vn + 15% Vn +25/- 30% Vn +/- 40% Vn + 40% 5%
Duration
Continuous Continuous Continuous 0.1s 1.0s
Continuous EN 50155 also accounts for long and complete
voltage interruptions. Equipment must be able to operate through supply changeover with a 40% dip in supply voltage for up to 100ms unless otherwise specified. Complete interruptions are divided into three classes designated S1 through S3, with S2 being the default test level, as shown in the table below.
Class S1 S2 S3
Interruption time >0 ms
<= 10 ms >10 ms
<=20 ms <20 ms
• Category 2 – Bogie mounted equipment. • Category 3 – Equipment mounted to the axel or wheels of the railway vehicle. The category determines the severity of the
testing that is required. Category 2, class B is the default requirement. Electromagnetic Compliance: Electromagnetic
compatibility (EMC) testing is usually mandatory and covered in EN 50121-3-2. EMC includes requirements for both emissions and immunity. The limits are based on the port type (battery source, auxiliary source, measurement or control, or communication). Performance and reliability: Railway
applications always involve people, and performance and reliability are key enablers of both safety and quality. Power supplies, unless otherwise declared and documented according to
Performance Resume normal operation after interruption
Maintain normal operation throughout interruption Resume normal operation after interruption
Maintain normal operation throughout interruption Resume normal operation after interruption
Table above: Supply voltage interruption classes introduced in EN 50155:2021
INDUSTRY FOCUS
make it difficult to be certain which power supply is best for your design. Selecting a power supply from an experienced and knowledgeable supplier is crucial.
POWER SUPPLIES FOR RAILWAY APPLICATIONS Power supplies are critical elements in rail system design and proper selection is fundamental to rail safety. The fact that multiple standards apply simultaneously makes the selection more complex than it otherwise would be, so consulting an expert vendor is recommended. Choose 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 ensures that its products keep pace with the ever-changing safety requirements. The reputable experts and engineers at Melcher can therefore assist with finding the optimal EN 50155 compliant power supply solution for your railway applications.
Common electronic systems in railway
applications
Environmental conditions: There are six
possible operating temperature classes, shown in the first table, with a default level of OT3. Any power supply solutions must also operate across a temperature range of 40°C to +85°C for at least 10 minutes during start-up, and temperatures must be managed in environments where there are extreme fluctuations. As of the 2017 edition, rapid temperature variations are taken into account. These variations can occur when trains enter and exit tunnels and apply primarily to equipment mounted outside the vehicle body. Shock and vibration: EN50155 references EN 61373:2010 for shock and vibration testing. That standard outlines allowable tolerance levels by breaking them into three categories: • Category 1 – Equipment mounted directly on or under the body of the rail car.
the standard, must have a useful life of 20 years. 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. Complying with a standard as complex as EN 50155 can
Bel can also create a custom version of its 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.
Bel
www.belfuse.com
JUNE 2024 DESIGN SOLUTIONS 23
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