Ethernet communications links are now being widely used both within trains and for inter-car connections. The first generation of these interconnectivity solutions was developed to link systems for functions such as passenger information, entertainment, security (CCTV) and automatic passenger counting, and were largely based on 100Mbit/s Ethernet technology running over cat 5 cabling.

As both communication technology and the economic and regulatory needs of the marketplace have evolved, there is now a need for further expansion in the capabilities of these networks.

Additional capacity is needed to meet the requirements of advanced train control systems such as ETCS (European Train Control System), driver-only operation, train-wide data monitoring, and new public access services such as Wi-Fi. More significantly, there has to be clear physical separation between critical and non-critical networks in many cases, so that systems responsible for train control and safety functions are fully protected against potential cyber attacks via the public access network.

In performance terms, current Ethernet networks on board trains are operating at 100Mbit/s and 1Gbit/s because this is the maximum practicable speed that can be achieved with the current generation of Ethernet switches.

However, train manufacturers are looking to the future, so all new designs are specifying 10Gbit/s to allow for the higher speeds that will result from technological developments and the requirements of new applications.

Inter-car jumpers

A key element in the on-board network is the inter-car connection, and this is an area where Harting has been able to develop an integrated modular solution that addresses the challenges outlined above as well as providing ‘future-proofing’ for the next generation of trains.

This solution is based on an ‘open’ Han® 24 HPR hood and a range of inserts from the Han-Modular® family. The standard HPR housing has been approved by the rail industry and is already in use in the field. A threaded locking mechanism enhances stability and provides good protection against shock and vibration. Strain relief is achieved using a clip or a corrugated conduit adapter.

Shielding from several cables can be attached to shielding rings or clamping brackets to reduce cost. Instead of using bulkhead or surface-mounted housings, the interface at the car end is screwed directly onto a mounting plate, which results in a significant reduction in cost and weight.

For this application, Harting supplies a fully preassembled and tested inter-car connection, pluggable from both sides by using the open hood, along with mounting plates which are attached to the walls of the cars. The most popular module is the Han Quintax® module, which is part of the highly successful Han- Modular® connector range. The Han DD module is used for analogue and digital data signal transmission, and the Han 46 EE monoblock is designed for medium-power applications. Corrugated conduits, which protect the cables, are attached to the open hood using M40 threaded connections.

Han-Modular, Han Quintax and Han EEE inserts in HPR upper and lower housings are fitted onto the power and signal cables that are routed through corrugated plastic conduit. In some cases, top-entry upper housings are used which mate with lower housings that are mounted on existing angle plates to optimise cable routing. The wires are protected inside the conduits to minimise the risk of abrasion. A pivoting threaded conduit connection is used to accommodate the dynamics of the application.

Interference must be avoided between the power and signal lines which are routed very close to each other. However, the EMI immunity of this system has been demonstrated during system testing.

Future-proofing

These robust jumper cables and customisable connectors provide sufficient bandwidth to allow expansion to accommodate the demands of future higher-performance communication networks. Using Han HPR connectorswithgrounddisconnect,thesesolutions provide full 10Gbit/s transmission tested to IEEE 802.3. They are compliant with fire regulation EN 45545 – 1, 2 and 5 and EN 50155:2007 to ensure reliable application on rolling stock, and offer industry-leading IP68 (submerged under pressure) and IP69K (high-pressure steam lance) sealing capability.

Harting also carries IRIS certification to meet the stringent demands of the rail industry. This includes certification to IRIS Version 02, which covers trackside use as well as rolling stock.

The modular nature of the Han HPRfamilygivesusersthe ability to mix signal, data and power interfaces in a single connector, along with the flexibility to incorporate up to six 10Gbit/s links in the connector.

The modular Gigabit jumpers have been developed and manufactured by Harting Integrated Solutions, a division of the company which designs and manufactures backplanes and backplane systems as well as customised cable assemblies for a wide range of customer-specific applications. The group’s activities range from design simulation and validation to comprehensive system testing.

Power to PCBs

For the rail industry, Harting offers a complete range of design and build solutions with the emphasis on saving space and weight. To complement its connectivity products covering high-speed data transmission at speeds of 40Gbit/s or more, the company has developed a number of techniques for providing power to PCBs on board trains, on platforms or trackside.

Backplanes and passive PCBs are used to link the power supply to connected devices as well as their normal use for carrying data and signals. A range of connectors handles the necessary current levels for different applications and designs. The Han connector family includes PCB adapters that can supply currents to the PCB from 7.5A to 40A. When combined with the company’s expertise in mechanical integration, this approach can save space and assembly costs when interfacing with I/O connections.

The Han-Fast® Lock is used for even higher currents, up to 60A, and is simply and easily locked in place with an integral latching pin, and released again if necessary.

Another connector in the Harting range, the compact har-flexicon® connector, is rated for currents from 6A to 17A and is available in pitches of 1.27mm, 2.54mm, 3.50mm/3.81mm, 5.00mm/5.08mm and 10.16mm/15.00mm. It is suitable for processing with reflow soldering, and offers both field-installable screwless push-in cage clamp style and insulation displacement termination technologies for single- strand wiring.

Harting can also supply ‘classic’ connector types for the combined transfer of signals and power. One standard DIN 41562 Power connector can transfer up to 40A together with signal and data, while the D-Sub Mixed connector, also rated at up to 40A, is an industry-standard I/O connector with a range of other high- current, high-voltage, coaxial and pneumatic contacts in addition to the standard signal ones.

Wiring replacement

HanOnBoard® is a connector technology which can replace standard discrete wiring by allowing power I/O connectors to be mounted and connected directly onto the PCB via a boarded-mounted adapter through which data, signals and power are distributed. This solution eliminates time-consuming and potentially fault-prone wiring and is based on an optimum combination of tried-and-tested Han components, PCB adapters and PCB solutions.

Because HanOnBoard is compact and weight saving in use, it offers additional benefits over traditional wiring. Printed circuit boards are more resistant to external influences such as shock and vibration compared with discrete wiring, and the total electrical path can be coated to provide enhanced protection. As a result, HanOnBoard solutions lend themselves to the harsh environments found in rail applications.

In addition to eliminating manual wiring, the use of HanOnBoard will also replace any potential wiring troubleshooting with quick module replacement and will help to avoid service faults. It can replace dozens of power cable interconnections, allowing distribution boxes to be made lighter and more compact. It will also help to reduce production costs through streamlined production processes and less material usage.

Having high currents routed in close proximity to sensitive PCB signal paths is a common problem that can cause problems in terms of PCB design and thermal management. Harting offers the expertise to overcome these issues by developing custom backplanes and passive PCBs.

As an example, in a typical recent rail project, Harting developed a rail-approved (EN50155) chassis for an embedded drive controller at lower cost than the existing customer product using a custom backplane, I/O and chassis.

Globally, Harting Integrated Solutions is a fully integrated system developer and manufacturer. The company has factories on three continents: Europe, Asia and North America. Each site has common equipment, tooling and procedures to provide seamless service to all the company’s customers worldwide.

Written by Mike Brookes, regional manager at Harting.