NEXT-GENERATION LED SIGNAL
Thales’ innovative LED signal transforms safety, choice and performance
Conventional electrically-powered colour light signals, which use filament lamps and coloured lenses to display different aspects, are a familiar part of the railway landscape. Colour light signals first appeared nearly a century ago and today, they remain the dominant channel by which instructions are conveyed from the interlocking to the train driver.
Because these signals rely on traditional incandescent lamp technology, they present infrastructure managers with a number of challenges. Lamps require frequent replacement, which makes maintenance expensive. They are also prone to in-service failure – a common cause of delays on railways. In addition to this, filament lamps are inefficient and need significant amounts of electrical energy to keep them lit.
We can provide any customer-defined colour simply by configuring the software
Thales’ multi-colour LED solution
brings together a number of major
Thales’ next-generation LED signal prototype addresses all of these challenges and provides main line and urban rail infrastructure managers with a cost-effective, low-maintenance and high-availability replacement for conventional incandescent colour light technology.
Single light point innovation
Thales’ multi-colour LED solution brings together a number of major innovations. One of these is its ability to display any customer-specified colour via a single light point. “This has the advantage of reducing infrastructure costs,” says Thomas Kiefer, Thales Germany. “Instead of three or four light points in the signal housing, you need only one.”
Thales’ solution incorporates unique optical supervision technology – a first for the signalling market. “This allows us to control both the colour and the intensity of the light,” says Mr Kiefer. “We can provide any customer-defined colour simply by configuring the software.” This includes green with a wavelength of 505 nanometres, vital in many signalling applications.
The next-generation LED signal is designed to provide maximum flexibility and it can be configured to meet any national or customer need. For example, signal profiles that require multiple light points can also be constructed. “The housing is fully selectable,” explains Alfred Warmuth, Thales Germany. “An additional benefit is that the same LED hardware can be used with any diameter of lens, from 70mm to 200mm.”
Energy and maintenance savings
Conventional lineside signals produce light using incandescent lamps, typically rated at 24W. “By contrast, our new LED signal is approximately 10W, so we are reducing the power consumption by around 50 to 60 per cent,” says Mr Warmuth.
LEDs also have the advantage of being much longer lasting than traditional filament lamps. Maintenance costs associated with lamp replacements are eliminated. “Today, lamps are changed every six or 12 months whether they need replacing or not,” notes Mr Warmuth.
Current LED technology promises a lifetime of about 10 years, but Thales believes this could be extended even further. “This is based on the fact that we manage the LEDs in an intelligent way,” says Mr Kiefer.
“The chips in LED circuits get very hot and LEDs degrade in direct proportion to their temperature. So our approach is to provide only as much power as we need to achieve a pre-determined optical output. The ability to vary the current to provide constant light intensity is a big advantage and it allows us to compensate for ageing.”
The ability to visualise and control asset status in this way plays a decisive part in optimising life cycle costs. “To extend the lifetime of such products, through-life diagnostics are vital,” says Mr Kiefer. “It also reduces maintenance costs for operators.”
A new safety approach
The introduction of any new signalling technology requires a long and careful evaluation of every safety factor before it can be considered for deployment. LED signals present a special challenge, because traditional lamp-proving techniques, which depend on current monitoring, cannot be relied upon to determine whether the lamp is lit or not.
“This was one of the main questions we asked each other at the very beginning of this project,” says Mr Warmuth. “We needed a new way to be sure that light was being emitted.”
Traditional filament lamps are ‘proved’ electrically. If the lamp ‘blows’, current is unable to flow and an alarm is triggered. The semiconductors used in LED circuits, however, are still capable of providing a path for an electric current – even when the LED unit has ceased to emit light.
“So instead of monitoring only current and voltage, we also monitor the light output using optical supervision,” says Mr Warmuth. “In this way, we can be certain the LED is lit.”
The creation of the next generation LED signal prototype was a joint project between Thales Germany and Thales Research & Technology (TRT) at Palaiseau in France. The collaborative approach – with experts from France and Germany working together – underlines Thales’ ability to pool its knowhow in order to drive forward customer-focused innovation.
|NEXT-GENERATION LED SIGNAL AT A GLANCE|
• Optimum availability – life cycle in excess of 10 years
• Multi-colour capability – one light point displays any required colour
• Energy saving – requires 50% less power than incandescent lamps
• Advanced diagnostics – including built-in optical failure detection
• Interoperable – can be used with any customer lens array and interlocking
Download brochure: FieldTrac 6365 Multicolour LED Signal