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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    How many times did your Dad tell you ‘always use the right tool for the job’.  It’s an old adage, but it applies equally to recommendations that we make to our customers.
    As a leading supplier of UPS systems in the UK & Ireland, Uninterruptible Power Supplies Ltd (UPS Ltd) are often asked about using our UPS range for centralised emergency lighting applications.  They can, but not without considerable oversizing.  Our recommendation is to use our PowerWave EL range of static inverters for this application – ‘..the right tool for the job’.
    The UPS Ltd PowerWave EL range covers both single-phase static inverter and three-phase static inverter applications and lighting load requirements from 500VA to 160kVA.  Passive Standby, Active Standby and No-Break operating modes are also supported, but what’s the difference?
    With a Passive Standby emergency lighting static inverter system, the lighting load is normally powered directly from the mains supply, but in the event of a power failure automatically transfers the load to the inverter.  A battery provides power to the inverter to support the lighting load.  As the system is sitting in idle until required, effectively on demand, there is an energy saving benefit.  Additionally, the system components are less stressed, so extending their working life and need less maintenance.  Passive Standby systems are ideal for use with fluorescent and incandescent lighting.
    As the name suggests, a No-Break emergency lighting static inverter system is always on, with the lighting load continuously supplied by the inverter.  This guarantees there is no changeover switching of the supply to the load when the mains fails and makes them ideal for maintaining high pressure discharge lights as well as fluorescent and incandescent lighting.  Further, the lighting load is unaffected by any variations in the mains supply and is constantly supplied with stabilised, smoothed and conditioned power, so the lights don’t flicker and lamp life is extended.
    A subtle difference with an Active Standby emergency lighting static inverter is that although the inverter is constantly running, it is off-load.  This design reduces stress on the inverter, subsequently reducing the risk of system failure at the critical time the inverter takes the lighting load at mains failure.
    ‘Safety first’, another old adage, is of paramount importance with emergency lighting systems, after all its prime function is for life saving.   As you would expect they are highly regulated and have to be compliant with the European Norm EN50171 Standard.  All UPS Ltd’s PowerWave EL static inverters comply.
    Another critical area of compliance required by the EN50171 standard is for static inverters to support a continuous overload if there is a circuit disruption within the emergency lighting system.  The PowerWave EL static inverter range all have a high overload capacity and are able to support continuous overloads of 120% of the nominal power rating.
    Equally important to choosing a static inverter is making sure it is supported over its life by regular service and maintenance.  A well maintained static inverter will ensure the integrity and availability of the emergency lighting system when it is needed and is essential for both safety and peace of mind.  This philosophy applies equally to batteries, which are at the heart of any centralised emergency lighting system.
    Battery duration is deemed by the specific requirements for each emergency lighting installation, but a long autonomy of three hours is typical.  That means a significant amount of batteries and it is essential a robust battery care regime is used to ensure they provide a reliable power supply when a mains failure occurs.
    On top of regular & periodic battery service, UPS Ltd are seeing a trend towards the adoption of our PowerNSURE dedicated battery monitoring, management and care system within the centralised emergency lighting systems we supply.    PowerNSURE monitors the condition of every battery individually and regulates the battery charging process to avoid under-charging, guaranteeing the availability of batteries at all times.
    So a number of key considerations with respect to static inverters and batteries for centralised emergency lighting systems.  It is all about ‘…choosing the right tools – product & service - for the job’.
    Alan Luscombe is Marketing Director here at Uninterruptible Power Supplies Ltd. To see all the Directors Blog Posts please follow this link
  • Uninterruptible Power Supplies Limited, is among the winners in the RoSPA Occupational Health and Safety Awards 2014.
    The Gold Medal (8 consecutive Golds) award has been received in the prestigious annual scheme run by the Royal Society for the Prevention of Accidents (RoSPA).
    As the UK’s family safety charity, RoSPA’s mission to save lives and reduce injuries covers all ages and stages of life. In support of this mission, the RoSPA Awards, which date back 58 years, recognise commitment to continuous improvement in accident and ill health prevention at work. Through the scheme, which is open to businesses and organisations of all types and sizes from across the UK and overseas, judges consider entrants’ overarching occupational health and safety management systems, including practices such as leadership and workforce involvement.
    David Rawlins, RoSPA’s awards manager, said: “The RoSPA Awards encourage the raising of occupational health and safety standards across the board. Organisations that gain recognition for their health and safety management systems, such as Uninterruptible Power Supplies Limited, contribute to a collective raising of the bar for other organisations to aspire to, and we offer them our congratulations.”
    Modern society is built on a foundation of data, with data centres becoming the lifeblood of health authorities, banks, government departments, retail outlets and almost every other entity that touches our lives. As Uninterruptible Power Supplies Ltd (UPS Ltd) explain, a reliable UPS will guarantee this essential flow of continuous, clean power to the data centre and other IT facilities, no matter what happens to the power supply.
    No critical data centre operates without an effective UPS and increasingly, even non-critical loads are relying on UPS systems to maximise availability and ensure a true no-break solution. ‘Zero down-time’ is now often an essential aspect of data centre operation. To attain this level of security, a continuous supply of clean power must be guaranteed, of which the UPS is a key component.
    UPS Ltd’s latest UPS system, the PowerWAVE 9500DPA, has been designed from the ground up, specifically to guarantee that data is available 24/7. UPSL has a range of high efficiency UPS products that cover the full breadth of applications, including data centres of all sizes. Because UPS reliability and zero down-time are so crucial, these features have been made cornerstones of UPS Ltd’s UPS design philosophy. Furthermore, because data centres now consume more energy than some major industries, data centre operators greet the significant reduction in energy bills achieved through high efficiency UPS systems with open arms.
    UPS Ltd’s newest UPS offering continues this tradition. With its standardised modular approach, low power consumption and high reliability, the PowerWAVE 9500DPA provides a UPS solution well suited for all types of data centres from 100kW up to 3MW.
    The decentralised parallel architecture (DPA), upon which the PowerWAVE 9500DPA is based, refers to each 100kW UPS module containing the hardware and software required for full system operation. The modules share no common components, with each module containing its own independent static bypass, rectifier, inverter, logic control, control panel, battery charger and batteries. With all the critical components duplicated and distributed between individual units, potential single points of failure are eliminated. In the unlikely event that one UPS module does encounter a problem, the overall system will continue to operate normally, but with one less module of capacity. The failed module will be fully disconnected and will not impact the remaining operating modules.
    This modular approach means you can size the UPS to exactly fit your needs and simply add modules as your requirements grow. Adding capacity is easy - five 100kW modules can be mounted in one frame and six frames can be configured in parallel to provide a top rating of 3MW. The PowerWAVE 9500DPA is the only modular UPS on the market that can easily add increments in this way. The resulting savings in power usage over the service life of the UPS are substantial. A further advantage is that the modular approach makes it easy to add redundancy and to further augment availability and reliability.
    The PowerWAVE 9500DPA modules are truly ‘hot swappable’, meaning they can be removed or inserted without risk to the critical load and without the need to power down or transfer to raw main supply. This feature directly addresses continuous up-time requirements, significantly reduces mean time to repair (MTTR), reduces inventory levels of specialised spare parts and simplifies system upgrades. This approach also pays dividends when it comes to serviceability and availability - swapping of online modules means you don’t have to switch off during replacement, so there is no down-time. This all leads to better risk management and an affordable, yet efficient, after sales service, hence the lowest total cost of ownership in its class.
    The straightforward concept of the PowerWAVE 9500DPA simplifies every step of the deployment process - from planning, through installation and commissioning to full use.
    This hot swap technology, along with significant reductions in repair time, can help achieve so-called six nines (99.9999%) availability - highly desirable for data centres in pursuit of zero down-time.
    UPS Ltd’s PowerWAVE 9500DPA operates with an efficiency of up to 96% or greater than 99% in Eco Mode. Its efficiency curve is very flat so there are significant savings in every working regime. This gives this particular product the lowest total cost of ownership of any comparable UPS system.
    Further, cooling costs in data centres are substantial. Because it consumes less power, the PowerWAVE 9500DPA requires less cooling effort, generating further savings. It also has a compact footprint - well suited for data centres, where real estate can be limited and expensive.
    Standardisation and modularisation have revolutionised the design of power back-up systems for data centres. Today, power systems for applications large and small can be built by using the same pre-designed, pre-manufactured and pre-tested sub-systems as building blocks. Standardising UPS systems to serve load segments of different sizes is now a reality. The benefits are clear - faster implementation, flexibility, scalability and controlled capital spending. Standardisation also enables the use of ready-made interfaces and management modules and simplifies integration with other data centre systems, such as UPS Ltd’s data centre monitoring software.
    Data centres of different sizes or in different phases can now apply one standard product. The PowerWAVE 9500DPA opens this new door because it not only provides load protection for data centres up to 1MW, but it allows easy expansion to a much higher rating (up to 3MW) - and all by adding standardised additional modules. Standardisation and modularity will drive new UPS designs and we will see further refinement of the decentralised parallel architecture, higher maximum power ratings and even more energy efficient solutions.

    Superficially, sizing a UPS appears to be simple; add up the total kVA requirement of the critical load and allow for some spare capacity to arrive at the UPS’s kVA specification. Although this approach is certainly an essential starting point, there are other factors that must be understood and allowed for to establish the UPS’s true sizing requirement.

    Most electrical equipment items have labels displaying their electrical characteristics. This information can be collated, and should include required supply voltage, number of phases, load current, power factor and power consumption. The number of phases is important, because if any part of the critical load is three-phase then a three-phase UPS becomes essential. A three-phase UPS can, however, supply both single – and three – phase equipment items.
    kVA ratings can be noted and totalled using an online tool such as the UPS kVA Load Estimator.
    For a more accurate view of the actual load and how it varies over time, a site survey using portable measuring and monitoring equipment becomes vital. Many UPS suppliers offer this service, including UPS.

    Historically, loads have tended to present an inductive or lagging PF, typically of around 0.8. The more recent shift to blade servers and other equipment using switched mode power supplies (SMPSs) has resulted in load PFs approaching unity or even becoming capacitive or leading. Legacy transformer-based UPSs derate substantially under these conditions, while modern transformerless types are less affected. Fig. 1 below shows the impact of PF on both UPS topologies. Note that modern transformerless UPS, in this example, need no derating at unity PF; the 300 kVA system can deliver full 300 kW power while the transformer-based equivalent is limited to 240 kW.
    Transformerless UPS
    300kVA Legacy
    doubleconversion UPS
    Power Factor (load)
    kW Rating
    kW Rating
    0.80 lead
    0.85 lead
    0.90 lead
    0.95 lead
    0.95 lag
    0.90 lag
    0.85 lag
    0.80 lag

    Increasing SMPS efficiency has created increased harmonic content in the load. All computer power supplies must have at least passive power factor correction to comply with EU standard EN61000-3-2. Equipment that imposes harmonic distortion can also create other problems such as high or pulsed currents during normal operation or start-up. Known ‘problem’ equipment in this area includes laser printers and some types of lighting.

    For three-phase UPSs, balancing the load across all phases is important to ensure that the UPS’s rating is fully utilised, as well as presenting a balanced load to the mains or generator if the UPS is bypassed. Most modern UPSs do not require careful phase balancing to operate correctly; even so, the load on any single phase must never exceed 33 per cent of the UPS’s total rating.
    Computer network equipment can create very high currents in the neutral conductor of a three-phase Y power distribution system even if the loads are apparently balanced. This problem typically occurs when single-phase computer units with non-linear load characteristics are connected across line L1, L2 or L3 and neutral. High neutral currents can cause overloading of feeders and transformers as well as voltage distortion and common-mode distortion.

    Some equipment such as motors can cause problems through inrush current as well as the harmonic distortion mentioned above. If such devices lack soft-start circuits, they can draw up to 15 – 20 times their steady-state current, as Fig. 2 shows. Significant oversizing of the UPS is required to support these high-inrush loads.
                                  Fig.2: Typical computer in-rush current

    As we have seen, UPS topology is important, because transformer-based types are so much more adversely affected by poor power factor loads than their modern transformerless equivalents.
    However, modular transformerless installations offer future-proofing benefits too; because additional modules can so easily be plugged in to the UPS frame as need arises. This means UPSs do not have to be excessively oversized during initial installation but are adaptable to cope with future power demands.
    Incrementing UPS capacity using small modules allows accurate UPS sizing even with built-in redundancy. For example, a load requirement for 120 kVA with redundancy could be satisfied with two transformer-based units of 120 kVA each in a 1+1 redundant configuration. However, this represents 50 per cent excess capacity, while the lightly-loaded transformer-based UPSs operate at low efficiency. By contrast, the 120 kVA redundant requirement could be fulfilled by using four 40 KVA modules; this provides full load support with n+1 redundancy, while operating at high efficiency and only 40 kVA extra capacity.

    In some applications, the UPS may simply be required to support a safe system shutdown if the power fails. Other users will expect the UPS to maintain power throughout an extended blackout, allowing its load to remain in service. These diverse demands on autonomy will affect the size of the battery needed, possibly increasing the UPS’s overall footprint.

    There are many factors to consider when sizing a UPS accurately for your particular site conditions. A knowledge of the critical load’s total kVA requirement, although essential, is not sufficient. The topology of the UPS itself can affect the sizing requirement, as can the electrical environment in and around the target site. Current and future expectations of the UPS’s role must also be taken into account to ensure that the UPS is correctly sized and future-proofed.

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