Interconnection opportunities in the rail sector abound as investment booms

While Europe remains the world's largest market for rail equipment, Asia is investing heavily in its own railway networks and networks in Africa, the Middle East and Latin America are also set to double in size over the next ten years. Ideally, connectors should be designed in at the start of any project: as soon as the basic specification of the carriage and signal requirement is known, then it is possible to work out the electrical specification. Designers of rolling stock are setting requirements higher and higher and it is essential for the connector requirements to be considered as early as possible in the design process. But, in reality, this is not what happens. "Modular connector systems will allow for change and provide the flexibility that designers need to determine the final mix of power, signal and even coax and fibre at a late stage. It's not ideal, but that is the reality we're working with," says Gary Evans, manager of Astute's new Emech division. The UK supports a diverse range of subcontractors, according to Alec Sluce, connector product manager at Aerco. "Because expenditure is stable, many are able to commit to new projects, so turnaround on new designs is usually quicker than for other major market sectors. "New connector types are being introduced continuously, but certain key requirements remain constant, such as: low halogen/low smoke – typically meeting spec NFF16-101; high reliability/mating cycles; the use of positive coupling designs and higher spec turned contacts; as well as environmental sealing." Rail systems are very noisy electrical environments, so ensuring the integrity of the signal with minimal interference will require EMC to also be considered. "Naturally, anything used on the outside of the train or beside the track remains fairly heavy duty," suggests Sluce. "These designs need to be able to withstand high shock and vibration and limit contact fretting." Harting's Han M Plus range of heavy duty connectors, for example, incorporates a special covering designed to withstand ballast and impact strikes to protect the interconnection components mounted under the train. In an increasingly connected world, people now expect to use their smart devices, even when travelling by train. As a result, there is growing demand for Wi-Fi capability and for power outlets on trains. "As a result, we are seeing an increase in the amount of electronics in each carriage," says Evans. Operators want extra features within the rail vehicles to be able to offer passengers access to information throughout their journey, agrees Kevin Canham, products and applications manager at Harting. "This demands higher bandwidth for high definition quality information screens. The use of high speed networks within trams or carriages, supported by high data rate connectors, can solve this issue. The design of the connector for these applications is a key element in enabling fast and effective connections to be made without interruption on the network." Along with demands for Wi-Fi and power, carriages require information and safety systems, improved lighting and communications systems, so connectors capable of handling high signal speeds are necessary. Modular systems that manage power and signal in one shell and can provide screening are also in demand and EESeals can be inserted into existing connector bodies, providing EMC protection when required. "Carriages are not miniature, but they are still finite in dimension so there is pressure to reduce the space and weight of connector systems used in rail. One way to achieve such savings is certainly through the use of modular connector systems, which enable power and signal to be mixed within the same connector housing," says Sluce. "New composites are also being used for their light weight. PEEK is a thermoplastic that is 35% lighter than PTFE and can withstand higher temperatures. Aluminium connectors are also now being specified, instead of steel." With the only major train builder in UK being Bombardier, prospects for UK suppliers in terms of rolling stock are not as positive as they are for trackside applications. "Most of the build is still done abroad," says Sluce. "Whilst there has been a lot of press around Hitachi's move to the UK, it tends to favour the Harting rectangular design for most of its power distribution and so this, in turn, limits the scope for suppliers in the UK." Engineers face numerous technical challenges when designing connectors that are suitable for use in the rail industry. Where are the connectors to be located?; how can they ensure that their designs meet anti-spray requirements or are able to cope with high levels of humidity? Are they resistant to moisture, gases and corrosive atmospheres and can they handle high levels of vibration, corrosion and fretting? In light of those demands, a range of industry standards needs to be met and this means railway applications will need to meet specific quality and reliability standards. "Previously, companies such as the London Underground, Thales and Bombardier controlled all the specifications," explains Evans. "Now, we look to standards from other industries such as JN used in High Speed Switching for example in the UK, as well as adapting various Military/Defence specs, such as 5015." The volume of information required within railway systems has increased substantially and traditional connector technologies are not always able to support the transmission requirements for speed, integrity and distance so to address this issue companies have developed a range of modules for circular and rectangular connectors to fit with high quadrax contact technology supporting high speed communications protocols. "Demand for these services is very high and because certain performance criteria can be relaxed, new smaller designs which save weight and size and use plastic shells are being used. Major manufacturers, such as Hypertac, ITT Cannon and Amphenol, are all competing in this space with small rectangular plastic connectors, which still offer very high performance," explains Sluce. "Signals need to be high speed and reliable, so quadrax, twinax, triax contacts are increasingly used, as are Ethernet configurations in ruggedised RJ45 formats and M12 connectors." While the market is certainly buoyant, supplying connector solutions – whether for rolling stock, inter car connections, train communication systems, driver cabin equipment or doors and access devices – will continue to provide a testing set of challenges for engineers.