For Data Centres, power protection systems must be available every second of every day and therefore maximizing system availability must be the overriding objective of any installation. Availability is best described as the percentage of system uptime achieved in a year. To achieve maximum availability, all single points of failure within the UPS need to be removed. Over the years, many improvements have been made in relation to UPS technology and configurations to increase availability.
Availability requires duplication and redundancy which naturally introduces inefficiencies, thereby increasing energy requirements. For example: thirty years ago, the only way to achieve redundancy was to install a number of standalone UPS modules in a parallel topology. These stand-alone systems could be pretty big, for example: 60KVA UPS weighed around 600kg and was the size of a double wardrobe! In addition to the UPS modules were the associated battery systems.
The introduction of transformer-less technology in the early 1990s, by Filippo Marbach, dramatically increased efficiency, decreased size, weight and reduced costs. The true modular UPS concepts, introduced after the year 2000, resulted in even further improvements
The 4th Generation true modular UPS systems now available, provide a significant improvement over previous system designs. This is because each module contains all the power elements of a UPS – rectifier, inverter, static switch, display – and critically – all control and monitoring circuitry. This places it above other current designs that have a separate, single static switch assembly and separate control or intelligence modules as there is no single point of failure. Availability for our CumulusPower UPS which incorporates this Distributed Active Redundant Architecture (DARA) system is now ‘nine-nines’ or 99.9999999%. Hot-swap capability lowers the Mean Time to Repair (MTTR) to only around three minutes.
Scalability and flexibility are also important when installing a system to ensure the continual ‘right sizing’ of the UPS. A system which is too small will be overloaded, compromising reliability and availability. One which is too large will waste energy, be inefficient and costly to run. CumulusPower offers a flat efficiency curve across the whole load range, particularly at lower loads which are inherent in parallel redundant UPS configurations. CumulusPower offers 97% efficiency even at these low loads.
Duplication and redundancy of UPS components must also apply to the communication cables between UPS modules. The most simple communications bus is a single cable. If this breaks or becomes disconnected, the entire system could be compromised.
For this reason, the ring circuit was introduced to the majority of modern UPS systems. If the circuit breaks the signals can simply communicate the other way around the ring. The recent introduction of the Triple Mode communications bus increases system availability even further.
Like its name suggests, there are three paths of communication between UPS modules and frames made up of three separate ring circuits. Three brains communicate with three other brains – it’s the belt, braces and buttons approach.
We liken Triple Mode to the comparison of a tightrope walker. If a tightrope breaks, the consequences will be dramatic and far-reaching. In the same way, a single communications bus is far more precarious than a Triple Mode ring connection which is more like a bridge with multiple supports. Here the single points of failure are completely removed. Even if one or several bridge struts fail, the others will support the load. It does beg the question: how would you prefer to cross the chasm?
UPS technology has seen huge developments over the years. With reductions in footprint and increases in efficiency and availability, the Total Cost of Ownership is now significantly lower. The most modern UPS have become about as close to perfect as possible, keeping in mind there will always be some losses due to the very nature of switching. The incorporation of Triple Mode communications buses further mitigates the risk and moves us further towards power protection perfection.
The team at CENTIEL has been at the forefront of UPS development over the several decades. Our goal is clear: to achieve the ultimate availability of power for our client base. Our leading-edge technology, backed-up with our comprehensive maintenance contracts ensure our clients’ power has the very best protection at all times, now and in the future.
Originally featured in UK Power August 2018