Advance Electronics protects dot matrix motorway signs from unwanted power surges with TVSS module:
When Scrimsign Micro Electronics Limited (www.scrimsign.co.uk), one of the UK's leading manufacturers of dot matrix displays for the public and private sectors, found that its award winning signs were experiencing unforeseen failures, the company's research department concluded that this was caused by transients in the power supply.
Because many of Scrimsign's displays are located out of doors, in exposed areas such as motorways and harbours, the quality of the power supplied to these units cannot always be guaranteed. As such, they are often subject to power surges caused by lightning induced transients.
Normally very limited protection:
New research tells us that 88.5% of all power disturbances are caused by transient voltages. Moreover, even though it might be thought that data and production processes are safe, the truth is that they will have very little - if any - protection against this potentially disastrous phenomenon.
Scrimsign had already addressed this issue by installing a transient voltage suppressor device manufactured by a third party. These units were positioned at site locations deemed to be at a high risk from mains borne transients, but the problem still remained.
Which technology to use?
After consulting Advance Electronics, two issues were identified that could lead to the problem being unresolved. Firstly, because many of Scrimsign's electronic signs were sited, out of necessity on rock, this inevitably cannot provide a good earth contact. Secondly, Scrimsign had specified a competitor's transient suppression module that relied on metal oxide varistor (MOV) technology. It was this latter issue that was more of a problem than first appears.
Most transient protection equipment relies on MOV based technology. Their limitation is that MOVs are traditionally slow to react to the rapidly increasing current of a typical transient waveform, giving insufficient protection if used on their own. Moreover, just a single voltage spike can easily destroy these devices - leaving sensitive microprocessor-based components open to devastation. Only a properly designed TVSS module or power conditioner can offer completely reliable protection against the kind of environment that Scrimsign's designs are regularly sited at.
With the need to provide the utmost dependability firmly in mind, Advance Electronics recommended to Scrimsign the installation of one of its range of AGT constant voltage transformers (CVT) for each affected site. Fundamentally, the constant voltage transformer is a very straightforward device, with no electronic components. Its indestructible characteristic makes it an excellent choice for situations where variations in the quality of the power supply are all too regular, but where maintenance facilities are at a premium - ideal for the remote motorway and harbour sites that are typical of Scrimsign's installations.
Effectively immune from damage:
A constant voltage transformer is also ideal for protecting sensitive loads against direct lightning strikes on power lines, something that can occur all too frequently in the self same locations where outdoor signs are often mounted. Because the constant voltage transformer is self-protecting to its supply, and to the critical load connected to it, the unit is effectively immune to damage from the rising waveform of voltage caused by a typical lightning strike.
The constant voltage transformer is also useful for riding out momentary breaks in the mains. The microprocessor components contained in dot matrix signs are highly sensitive to even the shortest of interruptions in the power supply. Moreover, because the resonating circuit within a constant voltage transformer stores a limited amount of energy, this renders them ideal for filling in potential small gaps in the power waveform. In fact, an average constant voltage transformer will be able to cover a gap of about half a cycle in a typical situation. This will satisfactorily drive modern microprocessor based equipment over a short-term break in the mains power.
And Scrimsign's view? They are delighted that their signs can now be located anywhere that has a power supply, regardless of the quality of the mains.
Contact: Nathan Briggs
Advance Electronics Ltd.,
Advance Park, Wrexham LL14 3YR
Tel: 01978 821000
Email: [email protected]
Web: www.aelgroup.co.uk