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Modular Advantages

19 May 2008

Employing modular UPS technology in data centres has a number of advantages including energy efficiency and providing continuous power for mission critical applications, as Peter Bentley and John Bladon explain

HAVE YOU EVER WONDERED why modern jet aircraft are equipped with two, and in some cases four engines? ‘For extra power and speed’, is the most common answer. That’s one reason, but there is another, arguably more important one – to provide redundancy. Of the several meanings of the word, the one associated with engineering implies fault-tolerant design. Faulttolerant systems continue operating, even when one or more of their redundant components fail.

“UPS modules are related to a UPS system in the same way that individual engines are related to an aircraft’s propulsion system,” suggests Bladon. “The two roles of the engines may be regarded as being one for capacity and one for redundancy (1+1). Modular UPS systems may also have 1+1 and other more complex N+1 and N+n capacity-redundancy configurations - also referred to as parallel-redundant configurations.”

The introduction of transformerless UPSs into the market - single-phase UPSs in 1994 and three-phase UPSs in 1997 - paved the way for the development of rack-format modular UPS systems. “Transformer-based UPS systems were far too large and heavy to ever become modular,” says Bladon. “However, light and powerful transformerless three phase UPSs were perfect for rack-mount, modular configurations.”

The first three-phase modular UPS system, the PowerWAVE9000, was launched by UPSL in 2001. This development enabled the capacity of UPS systems to be extended to support the increased critical loads as data centres grow - system scalability. Additionally, by paralleling UPS modules in parallel-redundant configurations, the availability of UPS systems, and consequently the availability of the critical systems that they support, was very significantly enhanced.

Unlike aircraft engines, up-market UPS modules possess the property of ‘hot swappability.’ This means that UPS modules can be inserted and removed from UPS systems while they remain operational. In a parallelredundant configuration a module can be taken out of service for repair or maintenance while the remaining UPS module(s) continue to support the load. Due to ‘hot swappability’ there is not any risk or disruption to the critical load during this process.

“‘Hot-swappability’ of modules gives UPS systems the ability to continually match their capacity to the size of the critical loads they support. This ‘right-sizing’ delivers energy efficiency,” asserts Bentley.

State-of-the-art modular transformerless UPS systems – like UPSL’s PowerWAVE9000DPA - are highly efficient (95 to 96 percent efficiency between 25 and 100 per cent full load rating), have very low input current harmonic distortion (2 to 3 percent THDi between 30 and 100 percent full load rating) and attract low whole-life costs. They are also blade-server-friendly – capable of supplying loads with a leading power factor up to 0.9 without the need for UPS de-rating. Bladeserver- friendliness is an increasingly important consideration in data centres where the growth of the blade server population is continuing its steep upward trend.

Power consumption in most data centres is continuing to rise rapidly as a consequence of ever increasing round-the-clock demands for more IT services.

Bentley points out that corporations are having to strike a balance between complying with the Government’s vision for them to consider the economic, social and environmental impact of their activities, to become more aware of their corporate social responsibilities, and delivering the highest possible level of system-availability demanded by their customers.

Bentley says that as a consequence of the many benefits they provide, there is an increasing momentum for modular parallel- redundant (N+n) UPS systems in the market, especially in the data centre segment. “Today, over 70 per cent of the UPS systems that we sell are parallel systems. Three factors have brought this about.

“Firstly, early parallel UPS systems required system managers to assign individual UPS modules to either ‘capacity’ roles or ‘redundancy’ roles. Today’s systems have the capability to auto-configure, which means that their UPS modules operate in ‘capacity’ role if they have to, or in ‘redundancy’ if they could do. Secondly, the relative costs and physical size of UPS systems have significantly fallen. Today’s modular 200kVA parallel-redundant systems have a footprint of less than two computer room floor tiles and an impressive power density of 342kW/m2,” continues Bentley. And thirdly, the business or mission criticality (importance) of the loads powered by UPS systems has increased to the extent that parallel-redundancy is no longer a ‘nice to have’ – it’s an essential. UPSL’s hot swappable PowerWAVE9000DPA™ modular UPS system can provide 6 nines availability.”

Where continuous power is mission critical, UPS systems of the ‘true’-on-line parallelredundant hot-swappable modular variety just keep on flying.

Supporting a critical load at Maritz Europa
POWER BLACKOUTS, BROWNOUTS AND DROPOUTS can cause major malfunctions and interruptions in equipment and IT systems, costing thousands of pounds in lost business and data. Companies such as Maritz Europa increasingly rely on power protection systems to safeguard their business.

Since the introduction of its first power support system 10 years ago, supplied by Uninterruptible Power Supplies Ltd (UPSL), business services company Maritz Europa has enjoyed reliable power protection, vital in safeguarding important business applications. Part of the Grass Roots Group, Maritz Europa is a global provider of business services which improve employee knowledge and skills, increase morale through incentives, and create innovative events and communications materials for a multitude of campaigns.

For their first system, Maritz Europa installed UPSL’s PowerWAVE5000 system to support the entire infrastructure of its data centre, including web and database servers and communications equipment. As with most IT installations, its business has grown and there has been a need to increase the technology to support it.

“UPSL has supported us through specification, commissioning and training in our UPS systems, and has been a reliable partner to our business,” comments Jon Kilner-Smith, support technician at Maritz Europa. “To ensure consistent protection we chose to upgrade our UPS to the modular PowerWAVE9000. It has the advantage of being scalable, adding UPS modules in parallel to increase support to the load or adding security through redundancy.”

David Bond, MD of Uninterruptible Power Supplies Limited, commented: “As well as supporting the increased load, upgrading to the modular technology of the PowerWAVE9000 brings significant additional benefits for many of our customers. For example, the ‘hot-swap’ capability considerably reduces the mean time to repair. Consequently the availability of the UPS system and the critical load that it supports are enhanced. This is an important factor for Maritz Europa and for many businesses today looking to provide reliable customer service by minimizing downtime through the highest levels of power availability.”

The new PowerWAVE9000 solution will efficiently protect critical loads that have leading power-factors such as blade servers – as is the case at Maritz Europa – in common with an increasing proportion of data centres across the country.

An additional benefit that Maritz will gain from the upgrade is the capability to facilitate ‘rightsizing’. This ensures both energy efficiency and the correct loading for today’s needs without having to invest in over capacity. With the modular format, capacity can be easily increased as and when required.

Kilner-Smith added: “Although we’ve never had a total power outage, our on-line double conversion UPS system is vital as it continuously conditions the raw mains electricity supply. Our IT infrastructure is being protected from less obvious crash-inducing mains power conditions like voltage and frequency fluctuations. The IT infrastructure is of increasing importance to our business. We plan to supplement the autonomy of our power protection system by adding a diesel generator to provide sufficient support until mains power is restored.”

As David Bond explained, “For some critical loads, extended autonomy, rather than graceful shutdown, is the preferred option for dealing with a long-term power disruption. Having a power protection system that comprises a UPS system plus a diesel generator provides total continuity until mains power comes back online. Maritz Europa’s investment in our equipment has played an important role in ensuring the continuity of its business operations.”

● Peter Bentley sales director and John Bladon operations director at UPS Ltd Peter Bentley is also co-author of The UPS Handbook which is now in its third edition.

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