Feature: Rail electronics


The design challenges for electronic systems on board trains


By Jasmin Sommerfeldt, Mechanical and Thermal Design Engineer, Duagon T


rains still remain an important method of transport throughout the world – in some countries even the primary mode. Trains also evolve, with


new technologies added all the time, such as communications (Wi-Fi, etc), seat displays, video surveillance and more, all of which require more processing power, memory, power supplies, specific connectors, and more. But, higher density of components and modules for all these applications lead to significantly higher power dissipation, which then calls for better thermal management onboard trains, where space is already very limited. Due to the harsh environment and


higher component density, rail electronics face several demanding challenges, one of which is high temperatures and how to manage them in the limited space available. Embedded systems in the rail sector are expected to operate to 70o


cabinet, with a maximum air temperature around them of 85o


C. Tis applies, for


example, to a train standing still in direct sun with its air conditioning off yet most of its electronic systems operating normally. Te environment on board trains is


considered harsh for electronic systems, which are expected to be rugged enough to handle shock, vibration, dust and humidity – all in accordance with the EN 50155 railway standard.


C inside a 20 March 2023 www.electronicsworld.co.uk


More components, smaller space To house computing onboard trains, 19” racks are typically used – but maintaining them is also a challenge. Although there’s air flow around these cabinets, space around them is overcrowded with multiple systems, which limits that air flow. Tus, 19” systems now have their own fans, which in itself is a problem: fans have limited lifetime and must be easily accessible to be replaced – leading to the use of fan cassettes; see Figure 1.


Ten there’s the presence of dust in


this environment: to prevent it from being blown into the system by the fans, air filters must be used. Filters, however, can significantly reduce air flow from the fans, which also impacts cooling. And, the longer an air filter is in use, the more becomes clogged with dust, leading to an even more reduced air flow. For this reason, it is important that air filters are cleaned and replaced regularly. All of these parameters must be


considered during system design, making it a particularly challenging task.


Durability by thermal connection There are hard limiting factors for the computing power onboard trains, which include their maximum permissible power dissipation. New CPU series, such as the Intel Xeon W-11000E/ Tiger Lake-H (TGL-H) and the 11th generation Intel Core, have a TDP (thermal design power) scaleability from 25W to 45W; see Figure 2.


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