Open-access content Tuesday 9th July 2013
When choosing an uninterruptible power supply, FMs and IT professionals can have different priorities. However, new UPS technology may satisfy both groups of users, says Paul Norgate.
4 July 2013
Ask IT professionals what they need most from an uninterruptible power supply (UPS) and their top answers will almost certainly be: the best possible protection for their data; scalability to allow for future expansion; and, increasingly, support for virtualised IT environments.
Ask the same of a group of FMs and the emphasis will be a little different. Their priorities are likely to be biased toward energy efficiency and ease of maintenance.
This doesn't imply that IT professionals aren't interested in energy efficiency or that FMs are not worried about the protection provided by the UPS - it's simply that the two groups have different priorities. There are, in fact, many areas where they agree, such as the importance of comprehensive monitoring facilities.
Nevertheless, the differences can cause problems, especially in the increasingly common situation where FMs are responsible for choosing UPSs that support IT operations. In these cases, should the FMs go for products that suit their own priorities, or products that tick the boxes for the IT department? A new generation of mid-range UPS systems ticks the boxes for both FMs and IT professionals.
Taking the load
First, let's consider providing the best possible protection for loads and, therefore, for the IT system data. UPS systems based on double conversion topology are usually best in this respect, since, by converting mains power twice - first from AC to DC, then back to AC - they provide the best possible isolation between the equipment they are supplying and the raw power from the mains.
Such a process allows them to provide protection against all nine of the most common power quality problems: power failures, power sags and surges, under-voltage and over-voltage, electrical line noise, frequency variations, switching transients and harmonic distortion. For this reason, double-conversion UPSs are often preferred for IT applications.
But they have a shortcoming - they are less efficient than other types of UPS. This is because, as their name implies, they have two power conversion stages - and each stage introduces losses. Their relatively low-efficiency has, in the past, made double-conversion UPSs less appealing to FMs, who are understandably never happy with a product that increases energy bills.
Recently introduced technology addresses this issue through the use of new techniques to reduce losses in the conversion stages, achieving 95 per cent efficiency in double-conversion mode, where 90 per cent was the case with their predecessors. These new UPSs works by, in effect, feeding the load directly from the mains supply when this supply is within tolerance and problem free, but switching to full double-conversion mode within two milliseconds of a mains supply problem occurring. This transition is completely invisible to the connected loads.
Improved filtering and control algorithms have made these 'high efficiency' modes possible. Previously, 'dirty' mains power would have reached the critical load because the UPSs were not advanced enough to filter disturbances, but improved technologies and advances in the switching from high efficiency mode to standard online mode (typically under 10ms) means loads will not see any disruption in supply. It is also down to advances in IT equipment that allows this switching to occur without having any effect on the equipment.
The power factor
Another key feature of these new UPSs, which will particularly appeal to FMs, is that they are compact and, for a given rating, offer more useful power. This is because they have a power factor of 0.9, compared with the 0.7 to 0.8 typical of older units.
In simple terms, the power delivered by a UPS can be considered to be the kVA rating of the UPS multiplied by the power factor of the unit. This means, for example, that an 8 kVA new generation unit with a power factor of 0.9 can deliver up to 8,000 x 0.9 = 7,200 watts of useful power, whereas an older unit with the same power rating but a power factor of 0.7 may only be able to deliver up to 8,000 x 0.7 = 5,600 watts.
Previous generations of UPS operated at a lower power factor (pf) - for example, an 11kVA UPS with a power factor of 0.7 will only provide 8kW of 'real' power. But newer UPSs, such as Eaton's 9PX, at the same KVA will provide 10kW of real power, due to a superior pf rating.
Finally, the savings made in the operation of the UPSs have increased as the efficiencies have improved so much, jumping from 91 per cent efficiency to 95 per cent in standard mode and even further to 98 per cent in high-efficiency mode.
The development of intelligent management software allows users to remotely monitor and manage multiple UPSs across their networks from a single interface. This could be a vCenter or XenCenter dashboard or even a standard web browser running on a PC.
In short, close integration with the virtualisation platform increases productivity and operational responsiveness, as well as allowing the UPS system to trigger migration applications to transparently move virtual machines to an available server on the network as an aid to ensuring data integrity and eliminating downtime.
Support for virtualised IT environments is important for future-proofing as virtualisation is becoming increasingly popular - it is, in fact, estimated that around 45 per cent of SMBs in Europe, the Middle East and Africa have already adopted virtualisation.
Paul Norgate is Eaton's UK sales & marketing manager