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In the UK the use of Extra Low Voltage (ELV) signal drives is now standard where controlled pedestrian facilities are provided. However, until recently, the widespread use of ELV technology across whole intersections had not materialised, largely due to the severe limitations on cable lengths and numbers of signals that can be illuminated, if traditional incandescent signals are used at ELV voltage levels.
The Welsh Office was one of the earliest authorities to employ an ELV-style system, requiring that sites should use a 50V-0-50V lamp supply. This effectively produced 100V at the signals centred around earth. Although not strictly an ELV supply by today’s definition, it was considered to offer some electrical safety benefits, but also came with the limitations mentioned earlier.
Looking ahead, the development of more efficient LED signals now allows extra low voltage to be used without imposing significant limitations on intersection cable runs or numbers of signals that can be driven, allowing all the potential benefits of ELV systems to be realised in the ST900 ELV system. As well as offering significantly improved electrical safety, the ST900 ELV system offers real environmental benefits.
These include significant reductions in CO2 emissions due to lower power requirements, and reductions in raw material usage, resulting from the need for fewer street cables. The end result is significantly lower costs compared to traditional LED solutions, due to improved technology. It is these benefits that are currently driving the rapid growth of ST900 ELV systems around the world.
The ST900 ELV system is designed to reduce energy costs significantly, control busier and more complex junctions, and places greater emphasis on safety. ELV sites typically.
The ST750P family is closely related to the acclaimed ST900 range of Siemens high performance traffic controllers. It is optimised for use as a pedestrian controller and provides Pelican, Puffin and Toucan control strategies at both LV (230V) and ELV (48V) drive levels. The ST750 is due to release in early 2009 and replaces the ST700 controller.
In common with the ST900 controllers, the ST750 family is compatible with the whole range of Siemens street-furniture, including Helios LED signals, LED nearside signals and LED wait indicators, all offering significant power cost savings over conventional signals.
A complete ELV system is required in order to maximise the benefits that ELV can bring. Siemens offers a full range of ELV equipment to complete the family.