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Reliability, safety and operation under adverse and sometimes extreme conditions play a central role in train electronics. Railway systems operate in wide temperature ranges and are exposed to vibrations and shocks. The pantograph's up and down movement causes high-energy arcing, which leads to voltage spikes in the train's electrical system – a threat to any type of electronics. Voltage drops and the subsequent restoration of voltage are the triggers for strong vibrations due to the inductance of the 100-metre-long and longer carriage cabling. A failure of railway electronics leads to delays in the best case scenario and, in the worst case, can endanger human health and life. It is time to take a look at the influence and importance of selecting the right semiconductor components.

First of all, designers should consider safety margins that exceed the values commonly used in conventional industrial circuits. Rectifiers or MOSFETs operating in a 110 V DC system would normally be selected with a permissible reverse voltage of 200 V. For the voltage spikes mentioned above, the use of 400 V types or even higher values is not an exaggeration. It is advisable to use only avalanche-rated parts, as these parts are designed and tested to withstand a defined surge energy. Forward peak current and reverse peak pulse power are parameters that lead to immediate failure if their maximum ratings are exceeded. If the amount of energy is known, e.g. through measurements in the circuit and based on calculations, it is again advisable to select components that can withstand at least twice that amount.
The additional costs for these high-quality components are certainly money well spent, as they increase the reliability of passenger transport vehicles. The savings in negative follow-up costs associated with failures, fault analysis, redesign and repairs are strategically important.

Secondly, there is an area of application that requires the same high level of reliability and qualification, but which is often overlooked by railway electronics engineers. We are talking here about automotive environments and the appropriately qualified semiconductors. These components meet the strict AEC-Q101 standard and are specially designed to function reliably under adverse environmental conditions. This makes them particularly attractive for trains. They offer high reliability and a long service life, as they are subjected to intensive testing and ageing simulations. The components remain stable even at extreme temperatures and feature improved surge and short-circuit resistance. This reduces maintenance costs and ensures smooth operation of trains on the rail network – a desirable design goal. Despite higher acquisition costs, automotive components pay for themselves through lower failure rates, less maintenance and longer replacement cycles.

Thirdly, semiconductor manufacturers' expertise is available. Semiconductor manufacturers know which component is the perfect choice for your specific ecosystem and environmental conditions. Their FAE and QA engineers can tell you which qualification level is recommended for a particular application and inform you about failure rates and life expectancy. Manufacturers are fully aware of the built-in safety margins of their components, the parameter variations typical for each semiconductor, and their temperature drift.

Years of experience in special applications in specific environments can thus be integrated into customer products. 

In summary, above-average safety margins, semiconductors qualified for the automotive sector and early consultation with the manufacturer's experts are the right way forward.

The result is reliable, robust, long-term available and, in any case, safety-relevant designs. This contributes significantly to optimising operational safety, maintenance intervals and total cost of ownership in the railway sector.