Advanced Ups Technology Delivers Improved Power Efficiency From a Smaller Platform

Uninterruptible power supplies (UPS) have for a longThe transformerless UPS produces an input power
time played a vital role in data centre installations.factor much closer to unity and less load dependant
Commercial and industrial enterprises facingthan the transformer design. This reduces the
unrelenting and ever expanding demand for theirmagnitude of the input currents, in turn minimising the
online data processing resource have become steadilysize of the cabling and switchgear, and in some
more dependent on the quality and reliability ofinstances, reducing the electricity costs. The
power that only an online UPS can provide. Now,improved rectifier can also reduce the total input
developing economical and political trends are puttingcurrent harmonic distortion (THDi) in a three-phase
even more pressure on data centre operators toUPS from around 30% to less than 3%, considerably
source the most efficient and flexible power solutionreducing harmonic emissions and easing compliance
possible. Electricity costs are rising sharply due bothwith industry guidelines. Improved battery
to increasing per-unit prices and to increasingmanagement also becomes possible.
consumption as server capacity is added. More 
servers create more demand for limited floorspace.The savings in space and weight are even more
Meanwhile, businesses increasingly need tosignificant. Because a transformerless system
demonstrate their commitment to a green powereliminates both the 12-pulse rectifier and transformer
strategy and low carbon footprint.of the earlier design, the footprint of a 120kVA
 system shrinks from 1.32m2 to 0.53m2, while the
The good news is that recent advances in UPSweight is reduced from 1000Kg to 370Kg.
technology, particularly the change from transformer 
based to transformerless design, have allowedData centre operators can therefore achieve the
systems such as Uninterruptible Power Supplies Ltd'sspace, efficiency and green improvements they need
PowerWAVE Series to meet these stringentsimply by changing to a transformerless design. In an
demands. Transformerless design brings immediateexample with a 200kVA UPS supplying a user's load
benefits of more efficient power conversion from aof 165kVA, the total saving in cost of ownership
much smaller space; in addition it has allowedover five years can amount to nearly £41,000, with
Uninterruptible Power Supplies Ltd to build thesenearly 230 tonnes reduction in carbon emissions and a
benefits into a fundamentally better and more flexiblecarbon neutral offset of 353 trees.
UPS design approach. This evolution can be illustrated 
by comparing the transformerless design with the Apart from these immediate benefits, the
transformer based solution that it replaces.transformerless size factor has opened new horizons,
 by enabling the concept of the
Although different UPS topologies are available, thePowerWAVE9000DPA modular rackmountable three
most popular type is a static online double conversionphase UPS system, which comprises up to five
architecture. This design uses a rectifier to convertmodules within a single rack. Each module is a
the incoming mains to DC for battery charging, thencomplete, self contained UPS which can operate in
an inverter to convert back to AC to drive theparallel with, but independently from the others. This
critical load. During normal operation or mains failureconcept allows Uninterruptible Power Supplies Ltd to
the inverter feeds the load. If the battery isoffer users more flexible solutions with better
discharged or the UPS fails, the load is bypassed toredundancy, availability, resilience and scalability than
raw mains. This arrangement is equally true forany previously available solution.
transformer or transformerless design, with the 
difference being in the implementation of the rectifier,ENDS
inverter and battery circuits. 
 Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â  ./.About Uninterruptible Power Supplies Limited
The transformer designs use a phase controlledThe UK’s leading supplier of power protection
rectifier, which had several drawbacks. The DCsystems in United Kingdom, the Channel Islands, the
output voltage from this rectifier type wasIsle of Man and Ireland. It backs its PowerWAVEâ„¢
insufficient for the inverter to achieve the same ACproducts with comprehensive technical installation,
output voltage level as the incoming mains supply,commissioning and maintenance services.
which is why a transformer was essential as an 
integral part of the design. The transformer addsThe company has recently introduced the
significantly to the size of the UPS, while the phasePowerWAVE9000DPA Seriesâ„¢ which is the third
controlled rectifier is also bulky, as well as creatinggeneration of its renowned rack-mount modular UPS
input harmonic distortion and power factor problems.system. It also supplies standby generators, software
 to monitor and control uninterruptible power supplies
Recent advances in power semiconductor technologyand to control the orderly shutdown of critical
and the advent of the Insulated Gate Bipolarsystems.
Transistor (IGBT) device have made the 
transformerless UPS a viable proposition. The phaseIn addition to publishing an authoritative handbook on
controlled rectifier has been replaced by a freethe subject entitled The UPS Handbook (Published in
running rectifier followed by a DC converter whichOctober 2007 – 3rd edition), the company is an
boosts the rectifier output to a much higher level,Institution of Engineering and Technology Endorsed
allowing the inverter to directly produce an outputTraining Provider.
AC voltage compatible with the original input voltage. 
The transformer has been eliminated.Editorial contact:
 Richard Broughton
This elimination has a significant effect on overall UPSDryden Brown Limited
efficiency, improving it by about 5% to yield aBuilding 2, Shamrock Quay
substantial reduction in heat loss, electricity costs andSouthampton, SO14 5QL, UK
cooling costs. This 5% improvement appliesTel: +44 (0) 23 8022 9041
irrespectively of how closely to capacity the UPS isFax: +44 (0) 23 8022 7274
loaded.Email: info@dryden.co.
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