Pioneering solutions for total power protection

In today's 24/7 on demand world, mission-critical business systems must be available 100% of the time. Downtime cannot be tolerated, which is where an uninterrupted power supply can assist. At Uninterruptible Power Supplies Ltd, we pride ourselves on delivering industry-leading power protection solutions combined with service excellence to ensure systems are 'Always ON'.

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  • UPS generators are no longer just a backup plan. Today, they are considered a vital component of a company’s power protection policy, as sizing UPS batteries for protracted power blackouts is simply uneconomic and impractical. In choosing a generator for a data centre or other critical IT load application, a number of factors must be considered. These include the generator’s key components, environmental issues and the qualifications of the suppliers as well as compatibility with the UPS to be supported.
    In this article, Alan Luscombe, director at Uninterruptible Power Supplies Ltd., a Kohler company, discusses how generators work with UPSs, and the factors you must consider when choosing a generator as part of your power protection policy.
    Following a power outage, a UPS system with true online topology will be able to supply all the protection required - even for the largest, most critical loads, if sized correctly. The UPS dual power conversion technology is designed to filter out mains-borne disturbances, while the batteries maintain power during the initial blackout period. However, a UPS alone will not be sufficient if the blackouts are likely to protract and extend beyond the battery autonomy of the UPS. Extending battery autonomy to hours rather than minutes can be prohibitively expensive, especially as there is little value in powering a critical load but not its cooling system.

    UPSs and generators working together

    In some applications, it may be acceptable to use the battery autonomy to gradually reduce the load if the blackout time is extended. However, for critical applications that must remain up and running through power blackouts of any length, a matched UPS-generator arrangement becomes the only practical solution. To ensure continuity of power throughout a blackout event, UPS, generator and an Automatic Mains Failure (AMF) Detection panel are needed to work together. When the mains initially fail, the UPS batteries support the load during a pre-set AMF delay time. If this period expires, the generator starts up and the UPS detects the generator power, using it to feed the load and recharge the depleted batteries. The generator runs until mains power is restored and stabilised, and is then shut down under AMF control while the UPS reverts to mains. UPS battery power covers the short power interruption during this transfer.
    A backup generator set comprises a stored energy source, an engine, an alternator, a control panel and the AMF panel. Although both gas and diesel-powered engines are available, standby generators are normally diesel-powered. Engine suppliers include John Deere, Volvo and Mitsubishi, for which different control panels with varying capabilities are available. Standard types provide automatic and manual generator control while providing the basic indication of operational parameters, which includes voltage, frequency, coolant temperature, oil pressure and battery voltage, plus alarm and fault indication. More advanced panels offer more sophisticated user interface displays and enhanced diagnostic capabilities. Remote monitoring and control via Ethernet, RS485 or USB ports as well as fault-finding and alarm diagnostics are also possible.
    Whichever configuration is chosen, generators must be compatible with the UPS and all other power equipment to guarantee an uninterrupted power supply. Ensuring compatibility can be considerably simplified by sourcing UPS and generator from a single supplier, who offers proven, matched generator/UPS sets. An issue can be the generator output frequency.  If its range is outside the UPS’s tolerance, the UPS cannot synchronise with the generator without endangering its load.  This problem can be avoided if the generator is known to be UPS-compatible and fully tested.

    Practical generator considerations

    When sizing the generator, it is important to consider more than just the UPS and its critical load. Cooling equipment for the load as well as emergency lighting, communications and alarm systems must all remain operational when it comes to a power failure. As a rule of thumb, the generator should be sized at one and a half times of the nominal UPS capacity for transformerless UPS systems. Additionally, three times the nominal air conditioning capacity should be provided.
    Since power failures are unpredictable, the generator must always be ready to start and support the load. Accordingly it must be kept warm, with a fully charged battery and sufficient fuel. It must also receive mains status signals to initiate its start-up and shutdown. Standby generators are kept warm by mains-powered engine water heaters or jackets. Mains are also used to trickle charge the battery. The status signals to initiate starting and stopping of the mains, is provided by an AMF panel. Another important factor is that the back-up generator has an electronic governor to ensure highly responsive control of engine speed and output voltage frequency.
    Any supplier that performs UPS and generator installations should offer advice and provide solutions related to important environmental issues and comply with regulations for safe fuel storage. Suitable noise attenuation housings have to be used to limit noises, especially since generators may have to run at night. Heat generation must be managed, with generators often sited outdoors in weatherproof enclosures. Provision must also be made for safe, unobtrusive removal of exhaust fumes.
    This article has explained why UPS/generator combinations provide the only practical protection from extended blackouts for critical loads, and described how generators and UPSs work together to provide an uninterrupted power supply throughout a blackout event. Practical considerations relating to UPS/generator compatibility, sizing, readiness and environmental concerns are also covered.
    To view our range of generators click here
  • When budgeting for uninterruptible power supply systems, it's essential to consider the total cost of ownership rather than just the original purchase price. If operating costs and upgrades are taken into account, an apparently lower-cost initial purchase can often be ultimately more expensive for the purchaser than a better-technology solution with a slightly higher original price tag.
    In this article Kenny Green, Technical Support Manager at Uninterruptible Power Supplies Ltd, a Kohler company, explains how better UPS topology can reduce the total cost of ownership and improve reliability while doing so.
    Most modern businesses’ reputation and survival depend ultimately on the quality and availability of their electrical power supply. Even brief power transgressions can take down any ICT equipment they reach, immediately disrupting any banking, purchasing or other transactions currently in progress. The Bank of England’s 2014 Q3 Bulletin notes that ‘Over 98% of sterling payments by value are made electronically….an (IT) infrastructure failure could greatly inhibit — or remove entirely — the ability of individuals and firms to make their payments. This would have severe consequences for economic activity’. The Bulletin cites power failures as a potential cause of such scenarios.
    Any operator faced with this possibility wants the best UPS protection technology available, while being aware that any funding request will be closely scrutinised in today’s economic climate. Fortunately, however, there is an answer to this dilemma; consider the UPS’s total cost of ownership rather than simply its catalogue purchase price. The best-performing UPS technology will cost a little more to buy initially than older products, but within a year the higher cost of the modular system is recovered.
    Although there are several reasons for this, they all relate to how UPS technology and topology have evolved. Accordingly we can look at this evolution and see how it generates cost-saving benefits alongside improved technical performance.

    Improved efficiency cuts costs

    Legacy systems used transformers, which made them large and heavy by today’s standards. For example a data centre with a 120 kVA load could theoretically have been supplied by a single, floor-standing 120 kVA UPS unit. In reality however, redundancy would probably be required to ensure better availability; this would be implemented with two 120 kVA units sharing the load in a 1+1 redundant configuration. As a result, neither unit could ever be more than 50% loaded, which for a transformer-based system meant a significant reduction in efficiency. It also meant investing in substantially more UPS capacity than actually necessary.
    The advent of transformerless technology has allowed much smaller and lighter UPS implementations – in fact to UPS modules that can be incrementally added to a racking frame to achieve an application’s required power capacity and redundancy. Free-standing individual units are no longer necessary. The 120 kVA load of the above example could therefore be satisfied by a single rack containing four 40 kVA ‘hot swap’ plug-in modules. The load remains fully supported with n+1 redundancy, while the total UPS capacity has been reduced from 240 kVA to 160 kVA.
    Although the purchase price per kVA for modular UPSs will be slightly higher than for legacy types, this difference will be partly offset by the reduction in purchased capacity and in floor space required for installation. However important savings in operating costs will also be made as the modular solution is more efficient than a transformerless implementation – especially one that cannot operate at more than 50% loading. Table 1 below shows that for our 120 kVA example, these savings will amount to over £38,000 for a five year operating period when the associated reduction in cooling costs is taken into account.
    Table 1: Legacy vs. modular transformerless UPS: Comparative operating costs over five-year period
    Although these savings alone will more than offset any difference in original purchase price, modular UPSs’ inherent efficiency can cut costs even further. Some UPSs are efficient enough to qualify for the Energy Technology List, or ETL. As part of the Enhanced Capital Allowance tax scheme for businesses, this government-managed list of energy-efficient plant and machinery includes UPSs as well as items such as boilers, electric motors and air-conditioning systems.  A business that pays income or corporation tax can claim 100% first year capital allowance on any ETL-listed product purchased. The ETL’s accompanying Energy Technology Criteria List (ETCL) has a complete section on UPSs. This defines and describes UPS technology, including the criteria for ETL eligibility.
    These ETCL criteria include UPS efficiency thresholds for eligibility at different percentages of full load for static systems of 10 kVA or more.Transportation costs themselves can also be halved, and installation costs can be considerably reduced, by using the smaller, lighter modular technology.
    During UPS operation, modular topology can also reduce ongoing costs due to spare part stock and logistics issues. Because traditional systems demand in-situ component-level repairs, maintaining a suitable set of spare parts is difficult and costly – especially as users tend to buy the most extensive and costly kit for maximum security. Even then, there is no guarantee that the kit obtained will be effective or contain the parts required for every possible failure that could arise.
    Modular systems, however eliminate these complications. Instead a single spare plug-in module will suffice; even when modules of different power ratings are being used, simply holding a module of the highest kVA rating installed will cover all eventualities, Training is simplified and less time-consuming, and trained technicians can swap modules within 15 minutes. Repairing by module-swapping in this way can save up to 50% on logistics and stock management costs.
    Modular system upgrading is also far simpler, faster and cheaper as extra capacity can be added simply by plugging in additional modules without even interrupting power to the critical load. The building work, increase in footprint and interruption to supply associated with extending traditional systems is eliminated.

    Hot swap modules and their impact on UPS availability

    So we can see that over time the modular solution becomes more attractive in cost terms – but does it compromise power availability by doing so? Not at all; in fact the reverse is true. A UPS’s availability is increased if its mean time to repair (MTTR) is reduced, and a key feature of a modular system is its minimal MTTR figure. If a hot swappable module does fail, it can be withdrawn from the UPS frame without even interrupting power to the load. A replacement module can be plugged into the rack immediately, reducing UPS repair time to as little as half an hour.
    By contrast, if a legacy system fails, it must be shut down, isolated from its mains supply and repaired in situ; a process that typically takes 6 hours to complete. This factor means that whereas a transformer-based system can offer ‘five nines’ (99.999%) availability, a modular UPS provides ‘six nines’ (99.9999%) availability. ‘Five nines’ equates to 2.5 minutes’ downtime per year while ‘six nines’ equates to 32 seconds.


    In today’s online commercial environment, power failures that bring down ICT systems are unacceptable, yet UPS systems, as significant capital equipment items, must be carefully cost-justified. Fortunately the best technology currently available need not be the most expensive, provided the total cost of its ownership is considered. In this article we have seen the technical, tax and logistics reasons why modular UPS technology, although initially slightly more expensive to purchase, becomes the most economical solution – while increasing UPS power availability - once all costs are taken into account.

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