A ‘break’ with tradition
01 June 2012
TE Connectivity’s enhanced generation of electrical circuit breakers for trains, which eliminate the disadvantages associated with conventional mechanical, pneumatic circuit breaker systems, is believed to be the world’s first all-electromagnetically operated system for 25kV and 15kV vehicles.
Five years in the development, more than 800 ‘VESA’ vacuum circuit breakers (VCBs) are now in service on four continents, proving their reliability in both high and medium-speed train applications and in a variety of climatic conditions.
All around the globe, public transportation markets are facing major challenges as the constant growth of urban centres puts pressure on commuter and travel times, creating a growing demand for greener and more efficiently engineered railway systems.
A worldwide ‘megatrend’ is the electrification of passenger trains, providing a more efficient transportation system that not only weighs less but also uses less energy. Electrically operated trains are therefore gaining importance in terms of transportation infrastructure mix, and rail engineers are increasingly looking to line power disruptive technology, which plays such an integral role in railway electrification.
TE’s rail and mass transportation business manager, Peter Van Loo says that only through close co-operation with its customers, was TE’s research team able to develop a system with breakthrough benefits for the railway sector. The VESA electromagnetically operated VCBs are not only lighter in weight compared with pneumatic circuit breakers, they are also easy to install, providing higher levels of safety and needing less energy to operate.
“Providing the market with a product that offers lower total installed cost while allowing the removal of bulky pneumatic systems, makes VESA an exciting and reliable product for both new designs and refurbishment programs,” he says.
Line power circuit breaker technology
Traditionally, circuit breakers deployed in the rail industry have been actuated by compressed air provided by a compressor and reservoir system that is independent from the main pneumatic supply to the train’s braking system. While this additional pneumatic circuit breaker system has been considered a proven technology for decades, such arrangements tend to be seen in a more critical light today due to their weight and space requirements, relative complexity, reliability issues and associated maintenance needs.
Pneumatic systems are less energy-efficient as air needs to be compressed and energy is dissipated in the form of heat loss. Actuating the circuit breaker with electric energy in one step eliminates the air compression stage and the energy losses that are associated with it.
The VESA VCB system needs less servicing than conventional pneumatic systems, and requires a smaller sized air supply and compressor for the pantograph actuation. In addition, the VCB is amongst the lightest in its class and is less than half the weight of some pneumatic alternatives.
The system has low electric power consumption for reduced power demand on the train’s low-voltage system. In addition, it offers traction energy savings from the significant overall weight reduction combined with reduced aerodynamic drag.
A VESA VCB can be retrofitted as part of a refurbishment, refit or major maintenance overhaul, and it can be customised in several ways, including the addition of earthing arms, the availability of various operating voltage options, integration of additional control relays and feedback switches.
TE estimates a savings potential of 120 maintenance hours per installed unit, thanks to self-cleaning insulators and a reduced reliance on pneumatic systems.
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