Modern Transformerless Modular UPS Systems

The modular approach that is now common in many datacentres and comms rooms is highly flexible in terms of adding new servers, cabinets and cooling but isn’t always nearly as easy to apply in terms of power protection. As energy costs and the provision of uninterruptible power supplies rise up the corporate agenda and budgets of most IT operators, modular transformerless UPS systems can help to alleviate budgetary pressures, especially when compared to more traditional transformer-based UPS products.

A sound and cost-effective energy strategy will off course look to secure power from the lowest-cost and most green sources available. However, datacentre operators still have to provision for the unexpected; mains power failures and potential power quality problems. The right strategy is to combine the right energy management strategy with a resilient power protection plan – using uninterruptible power supplies that can be right-sized from day one but with easy access to a scalable growth path.

Within a typical datacentre or data hall, space and power and two of the limiting factors that restrict the overall capacity available. As more powerful servers are introduced (even though more energy efficient than their predecessors) power demands also typically rise. Whilst floor space and the size of a building’s incomer are known, the difficulty for datacentre operators is how do they forecast future growth and ensure sufficient power protection and UPS capacity is in place from day one and for the years ahead. Moreover, the more energy efficient and scalable the UPS system, the more energy can be saved within the datacentre and the more flexible the overall structure. Adopting modular, transformerless UPS system designs can solve these issues. Not only do these more advanced systems offer higher energy savings than transformer-based uninterruptible power supplies, but they can be scaled both vertically (within cabinet) and horizontally (with extra cabinets) to meet future growth in power demands.

Transformer-based UPS Systems

Traditional static (rather than rotary) UPS have a built-in transformer. In some designs this does provide Galvanic isolation, which can be a benefit in industrial, and highly polluted mains power environments. However, there are downsides to the design including weight, size, noise and ultimately energy efficiency with most transformer-based UPS struggling to reach 93% or greater in energy efficiency along the complete power-demand curve. In addition a transformer-based UPS is typically installed within a separate plant or switchgear room with costly cable runs taken into the data hall itself to power the cabinet rows. Expansion can be costly at a later date as this can only be achieved through the additional of another matching UPS system and the installation of further cabling if not already installed on day one.

Transformerless UPS Systems

In contrast, transformerless UPS have advanced at a more rapid rate of development thanks to developments in power electronics including Insulated Gate Bipolar Transistors (IGBTs), which have been adopted in both the inverter and rectifier-booster stages. Not only does the use of IGBT technology help to reduce weight, size and cost but it also helps to improve energy efficiency and provide a virtually silent operation (apart from any cooling fan associated noise). In terms of efficiency, a modern transformerless UPS system can reach greater than 96% efficiency on full online mode and even 99% when run in eco-mode (a form of line interactive or standby topology – manufacturer dependent).

Modular Transformerless Uninterruptible Power Supplies

Modular UPS systems capitalise on the compact size and cost of transformerless UPS designs. The modular approach allows an entire uninterruptible power supply system to be expanded ‘live’ with the introduction of another UPS module into an existing cabinet. An example of this type of arrangement is the Eaton 93PM modular UPS system. An existing installation may be installed using one 40kW modular in a cabinet that can take another 40kW module without any associated downtime or electrical works required. The only factor that has to be built-into the configuration being the right-sized static on day one of installation.

This scalable modularity allows datacentre operators to retain floor space for their server cabinets and means that they only need to plan for UPS installation on the floor space either in-row or at the end of pod isles. If more isles are added, another Eaton 93PM modular UPS ssytem can be installed to server either another one or two server cabinet rows as well as be expanded to meet full cabinet population at a later date.

Modular uninterruptible power supplies now provide the type of upgrade path and flexibility available with other datacentre hardware systems. Whilst the cost can still be marginally higher than a non-modular UPS system, prices are falling and more manufacturers are introducing smaller module sizes. Potentially the future could see 10kVA module sizes and systems that can be economically expanded up to 200kVA and beyond. This approach is very similar to that adopted within the standby DC power system world and it is not beyond technical expertise to see this adopted within the AC datacentre world.