Note that BAS will not provide UPS capacity, though we will have spare built-in UPS capacity, in case unprotected equipment requires protection.  We are currently testing a MGE Pulsar EXtreme 3000VA. We purchased the rackmountable (4U) version (MGE part # 67840), rackmountable (also 4U) EXB-LA external battery extension module (MGE part # 67984), and hotswap BS socket outlet module (MGE part # 67952, or part # 67953 for IEC module), from Insight Direct (previously action.com) for £1864 incl VAT and delivery.

BAS generally uses the APC Smart-UPS systems

However, we found a tests comparison study (see results in HERE, and HERE, sorry, last article in French!), in which the MGE UPS scored higher for output stability and power management, and was rated top for protection in noisy electrical environments.  Despite its average scores, the APC Smart-UPS however offers the best quality/cost ratio.

Note that the MGE UPS is 'on-line', whereas the APC UPS is 'line interactive'.   The latter technology is a compromise between the 'off-line' UPS (only kicks in when the mains go off, no mains filter, cheap), and 'on-line' UPS (continuous double-conversion mains filtering, power out=~70% power in, expensive). 'Line interactive' is more effective than 'off-line', cheaper than 'on-line', and consumes 20-25% less current than 'on-line'.

BAS will have both UPS types (MGE and APC) at Halley.  CASLab will have two MGE Pulsar EXtreme 3000 (with EXB LA), one for the NOx rack, and one for the rest of core instruments (+ spare capacity).

When power budgeting to select/size your UPS, remember that the UPS instantaneous maximum apparent power (ie 3000VA) is not the real mean power (W), and that  W=power factor x VA.  MGE quote a power factor of 0.66 (2000W), whereas APC quote a power factor of 0.75 (2250W).

Also, check carefully the backup time of your UPS.  Our current UPS can cover a maximum of 30 minutes power out (the approx. maximum time for an unscheduled event). External battery modules can extend the backup time (modular UPS only), if you cannot reduce the number of components plugged in the UPS to increase the backup capacity.  If you do not want your system to go down, plan for 30 minutes.  If you don't mind your kit going down but in a controlled fashion, plan for a backup time sufficiently long to allow the controlled power down (this option is available for the MGE and APC). But remember power outs may only last few minutes, then we must restart your kit (not necessarily feasible in bad winter weather on the same day), or you should design your kit to restart automatically after a power out/UPS battery backup/mains recovery event. 

For more information, contact Stephane Bauguitte