01. April 2016

Gigabit jumpers: key links in new-generation on-train networks

Ethernet communications links are now being used widely both within trains and for inter-car connections (Fig.1). The first generation of these interconnectivity solutions were developed to link systems for functions such as passenger information, entertainment, security (e.g. CCTV) and automatic passenger counting, and were largely based on 100 Mbit/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, with additional capacity needed to meet the requirements of advanced train control systems such as ECTS (European Train Control System), driver-only operation, train-wide data monitoring, and new public access services such as Wi-Fi. More significantly, in many cases there has to be clear physical separation between critical and non-critical networks, 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 100 Mbit/s and 1 Gbit/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 10 Gbit/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 (Fig.2).

The HARTING solution for these applications is based on an “open” Han® 24 HPR hood and a range of inserts from the Han-Modular® family (Fig.3). 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 with a strain relief clip or a corrugated conduit adapter with strain relief. 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 project HARTING supplies a fully preassembled and tested inter-car connection, pluggable from both sides by using the open hood (Fig.4). HARTING also supplies 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 which 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. In fact, 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 HARTING Han® HPR connectors with ground disconnect, these solutions provide full 10 Gbit/s transmission tested to IEEE 802.3. They are compliant with fire regulation EN 45545 – 1, 2 & 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® HPR family gives users the ability to mix signal, data and power interfaces in a single connector, along with the flexibility to incorporate up to six 10 Gbit/s links in the connector.

Customised backplanes and jumper cables

The modular Gigabit jumpers have been developed and manufactured by HARTING Integrated Solutions: a division of the company that designs and manufactures backplanes and backplane systems (Fig.5) 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. In addition to connectivity products covering high-speed data transmission at speeds of 40 Gbit/s or more, HARTING has developed a number of techniques for providing power to PCBs on board trains, on platforms or on the trackside.

In addition to their normal use for carrying data and signals, backplanes and passive PCBs are used to link the power supply to connected devices. In order to handle the necessary current levels, HARTING Integrated Solutions uses a range of connectors that offer advantages for different applications and designs.

The Han® connector family includes PCB adapters from the Han® modular portfolio that can supply currents to the PCB from 7.5 A to 40 A. When combined with HARTING Integrated Solutions expertise in mechanical integration, this approach can save space and assembly costs when interfacing with I/O connections. 

The Han-Fast® Lock connector allows even higher currents of up to 60 A, and simply needs to be inserted into a plated hole provided for the contact which is locked in place with an integral latching pin and can be released again if necessary. 

Another connector in the HARTING range, the compact har-flexicon® connector, is rated for currents from 6 A to 17 A and is available in pitches of 1.27 mm, 2.54 mm, 3.50 mm/3.81 mm, 5.00 mm/5.08 mm and 10.16 mm/15.00 mm. 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. The DIN Power connector can transfer up to 40 A together with signal and data in one standard DIN 41612 connector, while the HARTING D-Sub Mixed connector allows a current of up to 40 A in an industry standard I/O connector along with a range of other high-current, high-voltage, coaxial and pneumatic contacts in addition to standard signal contacts.

HanOnBoard® is a connector technology from HARTING which can replace standard discrete wiring by allowing power I/O connectors to be mounted and connected directly onto the PCB (Fig.6).

With the HanOnBoard® concept, Han® connectors are connected to the board via a PCB 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 conformally 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. A PCB with HanOnBoard® 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.

A common challenge in the rail industry is presented by high currents routed in proximity to sensitive PCB signal paths, which 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.

A typical recent rail project handled by HARTING was the development of a rail (EN50155) approved chassis for an embedded drive controller at lower cost than the existing customer product. For this application, HARTING developed a custom backplane, I/O and chassis.

Global manufacturing

HARTING Integrated Solutions is active as a fully integrated system developer and manufacturer, including production. Operating a global manufacturing footprint, 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 global customers.


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