Today, on line UPSs are the most popular choice to support data centres, communications hubs and other applications using sensitive ICT equipment. They deliver power under all conditions and transfer to battery without power interruption if the mains fails. However there are still many applications with less critical requirements; these can benefit from the lower costs of an off line UPS solution.
In an article recently published in Electrical Review, Mike Elms, Technial Sales Manager for Uninterruptible Power Supplies, a Kohler company, compares on line and off line UPS topologies, together with a third variant, line interactive topology. We can highly recommend to read this article after the link below to everybody who is interested in making informed power protection choices.
Elms’ conclusion reads as follows:
“In summary we can say that for critical applications or those involving sensitive equipment, on line UPS topology is the only real solution, due to its delivery of conditioned power and seamless transfer to battery. For less critical applications, off line topology may be suitable, and is attractive due to its reduced capital and operating costs. Line interactive systems offer an improvement on off line topology, with better power conditioning and regulation, and reduced battery wear. Ferroresonant transformer line interactive solutions also offer seamless load transfer. Pressure to reduce PUE has increased interest in Eco mode operation, but this shares most of the characteristics and disadvantages of off line topology. The best possible power quality and availability results come from on line UPS systems designed into an overall power protection strategy.”