DATA CENTRE MANAGEMENT SUPPLEMENT FEATURE Optimising UPS energy efficiency
Modern, modular UPSs like Kohler Uninterruptible Power’s PowerWAVE 9250DPA offer excellent efficiency through their modular design – which is maintained even at low loads through Xtra VFI smart module switching
D
ata centre operators are under continuous pressure to improve UPS
energy efficiency – not only to control costs, but also to comply with government legislation and demonstrate a responsible green policy. UPS energy efficiency significantly
impacts overall site performance, as UPSs are major equipment items. This has improved over time, progressing from 94 per cent 10+ years ago to over 97 per cent true online operating efficiency today in systems like KUP’s PowerWAVE 9250DPA. This has been achieved through
technological advances including migrating from transformer-based to transformerless topology. Early UPS designs depended on a transformer to step up the inverter output voltage to a level compatible with utility or generator supply. However, power semiconductor
technology developments have eliminated the step-up transformer; this allows more efficient, smaller and lighter UPS designs. Overall, efficiency is improved by about
five per cent. The transformerless design’s efficiency curve is flat, and above 95 per cent, from 25 per cent loading to full loading. Transformer-based system efficiency is lower at full load, and drops away further towards 25 per cent loading. Transformerless energy savings are amplified because greater efficiency reduces heat losses, cutting the energy required for cooling. Nevertheless, if UPS loading drops below
25 per cent, energy efficiency can fall sharply. However, a smart solution known as Xtra VFI now addresses this. A modular double-conversion UPS with this mode enabled automatically adjusts the number of modules on line to match prevailing
load requirements. Superfluous modules are switched to standby but remain primed to start up if the load increases. The technique operates over the entire UPS load spectrum, but is especially valuable at loading below 25 per cent, where UPSs are least efficient. Another possibility is to operate the UPS
in ‘Eco-mode’, where under normal operating conditions raw mains power is fed directly to the critical load. The UPS only switches the load to inverter output if it detects a mains aberration or interruption. This improves efficiency, possibly up to 99 per cent, by cutting out the rectifier and inverter conversion stages, but exposes the critical load to the risk of power loss or damage.
Kohler Uninterruptible Power
kohler-ups.co.uk
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Make power interruptions a thing of the past with an expert team offfering exceptional levels of pre and post-installation support and best-in-cl best-in-class power protection equipment.
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