"Active filters are the way ahead in fighting mains corruptions," says Chris Cusick Mitsubishi Electric Automation Systems’ Drives Manager. "Their performance/cost ratio is unrivalled by competing technologies, and users are adopting them so rapidly that they will become the dominant type within a few years."
There are several types of filter currently in use, many having been fitted in the last few years since legislation was enacted to dissuade large power users from corrupting the mains supply with back-harmonics from equipment such as drives, UPSs and power factor correction units. The most common type is probably the simple choke, which has the attraction of being relatively cheap, but being only about 50% effective is often not able to achieve acceptable performance standards.
Very bulky traditionally:
Twelve-pulse bridge filters typically cancel out 80 - 90% of all harmonics, but are very bulky so cannot be fitted in installations where space is at a premium. Switched bridge harmonic controllers are the 'Rolls-Royce' of filters, achieving greater than 95% correction, but are out of reach of most automation budgets.
Active filters often match harmonic bridge controllers for performance, but at a fraction of the cost. In operation they absorb incoming harmonic currents, invert them and feed them back to the mains to 'neutralise' further currents, in the same way that noise reduction equipment functions in in-car entertainment systems. A notable characteristic is their very fast response to load changes, an area where all other technologies struggle to maintain performance.
Optimum performance:
Graham Brooks, MD of AIM Europe says: "Optimum performance is bred into the AIM active filters, a technology spun out of the original US Strategic Defence Initiative (or 'Star Wars' as Ronald Regan preferred to call it)."
AIM Europe is the overseas arm of APT AIM Energy, Inc., which develops commercial and industrial uses for the power quality technologies that originated in the US defence and aerospace programmes. Based in Scotland it provides sale and support across Europe. "Our new alliance with Mitsubishi means we can accelerate the roll out of active filters to a level driven by market requirements while backing this up with their comprehensive range of related products."
Mitsubishi will initially be introducing the technology to the water industry, which has some issues regarding harmonics that it has not been able to address adequately with existing technologies. But Mitsubishi expects interest from other sectors to be keen too.
Cusick sums up: "Active filters are set to cause a small revolution in mains quality maintenance so we have made sure we have all our back-up systems in place before going to market."
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