With Mid Size Data Centres popping up in the outer London Counties acting as back-up to the main inner London operation there are a number of Emergency Standby Power issues that need to be considered when attempting to meet the Tier requirements of these prestigious customers. The Generators and UPS Systems even with the latest IGBT UPS Input Rectifiers that have 3% THD and input power factors at full load of 0.98 still need to be rated correctly so that they work together in all load conditions.

Meeting the tier arrangements with so many UPS Systems, typically 12 providing data racks in N+1 and 2N redundancy with a further unit for Mechanical with each data UPS being loaded in normal operation at 20% still requires the Generator Power to be rated for the number of UPS Systems.

The UPS has to provide a high efficiency at 20% load, and also a good Power Factor. Its Harmonics produced by the Rectifier also have to be low, however even when all this is provided by the latest true on-line UPS Systems the Generator still needs to be either oversized or be provided with a larger Alternator to ensure all operational situations can be provided giving full reliability.

Email: Alan.fisher@avk-seg.co.uk