Data centers are getting larger, sometimes dramatically so. In Langfang, China, construction is under way at the Range International Information Hub. When completed in 2016, this commercial data center will become probably the largest in the world; covering 6.3m sq ft, it will be nearly the same size as the Pentagon. Other data centers of 1m sq ft  or more already exist across the US and other parts of the world.

Although these extremes are unusual, they reflect the growing trend for larger-scale processing facilities for enterprises of all types and sizes. We all increasingly rely on our smart devices and computers for our transactions, searches for information and socialising, while the past two or three years have also seen rapid growth in machine to machine (M2M) communications. According to a market research report published by MarketsandMarkets, the automotive and transportation data communication sector has the highest projected growth, with a compound annual growth rate of 33.5% from 2012 to 2017.

As enterprises gear their data centers to accommodate the capacity demand generated by these factors, they find that their power demand is increasingly being reckoned in megawatts rather than tens or hundreds of kilowatts. As these larger facilities come on line, their users have an even greater need for energy efficiency, green operation, availability and flexible scalability than that of smaller operations; the consequences of underperformance or failure grows with the data processing load.

Uninterruptible power supply (UPS) vendors are increasingly able to meet these larger requirements, by scaling their technology as required. One powerful approach is based on transformerless modular UPSs; while kilowatt-level modular systems have been widely established for many years, megawatt implementations have now become possible. We can see how UPS installations of all sizes can achieve the benefits they need by taking a closer look at the technology now available across all levels of power requirement.

Increased energy efficiency and reduced size and weight
When online UPSs first became popular in the 1970s, their design used an internal step-up transformer. These designs have remained popular for many years, especially for larger systems. However, the industry has more recently moved towards transformerless technology because of the advantages it offers.

Transformerless topology has become viable through advances in power semiconductors and the appearance of the Insulated Gate Bipolar Transistor. This has allowed UPS designs in which the DC level supplied to the output inverter is boosted; the AC output from the inverter is correspondingly higher, eliminating the need for the step-up output transformer that previously followed the inverter.

Eliminating the transformer has a significant impact on the UPS’s overall efficiency; as Figure 1 shows, this increases by about 5% to yield a substantial reduction in energy running costs and heat losses. We can also see that the transformerless efficiency curve remains flat for loads from 25% to 100%, while transformer-based UPS efficiency drops away steadily as loading decreases from 100%.

 

 

Figure 1: UPS AC-AC efficiency curves for transformerless and transformer-based topologies
 

Further efficiency savings arise from power factor improvements. The transformer-based systems present a lagging power factor to the incoming supply, which is well below unity at full load, and falls further with decreasing load. By contrast, transformerless UPSs present a full-load input power factor which is much closer to unity and remains load independent. Total harmonic distortion is reduced from about 30% to approximately 3%, virtually eliminating harmonic pollution of the incoming mains supply. Overall, the magnitude of the input currents is reduced, which in turn minimizes the sizes of the cabling and switchgear, and in some circumstances reduces electricity running costs.

Transformerless technology’s contribution to energy saving is matched by the substantial saving in size and weight that it provides. This is because transformerless systems eliminate the transformer, and operate with a much smaller rectifier. For example, a 120kVA transformer-based UPS has a footprint of 1.32m2 and weighs 1200kg, while its 120kVA transformerless alternative has a footprint of 0.64m2 and weighs just 310kg.

These physical factors have had a profound effect on UPS development because they are sufficient to allow UPS units of up to 100kVA to be implemented as rack-mounting modules instead of cumbersome standalone systems. This brings major benefits in terms of parallel redundancy, right sizing and extensive scalability. These advantages are in addition to the efficiency, energy saving and reduced cooling costs provided by the underlying transformerless topology.
 

The opinions expressed in the article above are those of the author and do not reflect those of DatacenterDynamics, its employers or affiliates.