One of the biggest changes in the rail industry has been the move away from dependence on diesel as the main motive fuel. With the increasing electrification of railway networks, train manufacturers are now looking for more innovative solutions and improved methods of "current collection".
As the electrification of the networks has developed, demand for additional vehicle or end-user specific functions, such as contact strip wear monitoring, is increasing. Development of new "current collection" solutions can make a significant contribution to meeting the following crucial needs of the rail market:
- Overall reduction in vehicle weight
- Increase in passenger space
- Initial acquisition and whole life cost reductions
The evolution of the pantograph
The pantograph is a familiar sight on the top of rail vehicles, a system designed to allow trains to travel at high speeds without losing contact with the overhead catenary lines. The pantograph arm pushes a contact shoe up against the underside of the power cable, which draws the electricity required to power the train. Typically, compressed air is used to control the basic raise, hold, lower and fast-drop functions of the arm.
The majority of pantograph systems require compressed air supply for their first lift after a vehicle outage period. This is because the vehicle’s main compressors are usually not powered up until the pantograph has an established electrical connection to provide system power.
Usually an auxiliary compressor can deliver the air supply, however, this approach means costly procurement, a need for physical space to install the compressor, plus installation time and ongoing whole life costs associated with servicing and maintenance.
To achieve this one of our expert team of designers eliminated the need for the auxiliary compressor by engineering a compact, fully integrated “plug and play” control system, containing all the pneumatic functions and incorporating a reservoir. The redesigned main control module system is linked to a 25-litre reservoir, charged during normal operation to 9 bar via a 2/2 solenoid valve contained within the module. The pantograph system draws compressed air for its initial operation from this reservoir.
The integrated 2/2 valve is vital for overall system performance. In its de-energized state it retains the reservoir’s air charge for up to 5 days, ensuring reliable pantograph operation after moderate outage periods. Cleverly, the provision of a separate external air supply connection allows the system to operate even after extended outages.
This innovative approach addresses some of the key market needs whilst enhancing whole system performance.
Reduced vehicle weight – the single plug and play module is designed to achieve all required functionality with a minimum space envelope and weight. The weight of the auxiliary compressor and its associated installation components such as mounts, connectors and tubing are removed.
Increase in available passenger space – the module is now small enough to fit in a reduced space envelope making its installation location more flexible to suit carriage layout. The space required for the ancillary compressor has been eliminated, increasing available space in the carriage.
Initial acquisition and whole life cost reductions – the initial acquisition costs are now lower and the vehicle initial installation costs are reduced due to elimination of the auxiliary compressor. A side benefit is process simplification demonstrated by a reduction in the number of component suppliers, orders raised and managed, as well as assembly and testing work because the control unit is supplied fully function tested, ready to just plug and play.
All of these factors have a positive impact on the total life time cost.
The benefits of a single module approach don’t stop at installation and procurement. It’s essential in today’s modern rail environment that service and maintenance times are kept to a minimum, optimising vehicle operational time and profit. Having only one module that can simply be replaced as a whole unit (rather than individual parts) is tremendously beneficial in terms of service and maintenance. Due to its plug and play qualities, the system can quickly be decommissioned, serviced, repaired and re-commissioned with ease, resulting in less down time.
Article contributed by Dave Walker, market development manager for Rail, Automation Group, Parker Hannifin Corporation.