The Evolution of UPS Systems

In the ten years since the formation of UPS Ltd. the world has gone online. Individuals and corporations demand access to voice and data services from anywhere at any time. Computer and communications hardware pervades organisations of all sizes, in densely populated data centres or alongside workers in office environments.

This growing hardware base has brought both political and commercial pressures to curb its accelerating demand for electrical power. From the Kyoto Protocol adopted by the United Nations Framework Convention in Japan just before UPS Ltd.'s formation to the UK government's current draft Climate Change Bill, legislation to promote a low carbon economy continues to appear. With power and cooling consuming typically 60% of a data centre's budget, and electricity prices rising, efficiency improvements have steadily gained priority.

With advances in UPS technology, systems have become more efficient with higher availability, while being more compact and aesthetically acceptable. UPS communication has also developed, from simple go/no go signals supported by IBM AS400 computers in the late Eighties, to complex status information now exchanged over corporate WANs or the Internet.

The traditional transformer based double conversion on line design UPS first appeared in the 1970s, and is still widely used. Meanwhile the first single phase transformerless systems appeared in 1994 with three phase versions arriving in 1997. Transformerless UPSs, even three phase models, are significantly smaller and lighter than transformer based designs, making them ideal for rackmount, modular configurations. The prime benefits of modular systems are twofold. Firstly, modules can be easily aggregated to closely match the critical load requirement, and more modules can be easily added to accommodate growth in the critical load over time. Secondly, modules lend themselves easily to parallel redundant configurations, which, when coupled with fast module replacement or even hot swappability, leads to very high power availability.

Transformerless UPSs also improve efficiency by eliminating transformer losses. Other benefits include low input current total harmonic distortion (THDi), low audio noise, near unity input power factor and efficient support of leading power factor blade servers. The drive to improve UPS efficiency is expected to continue to further reduce costs and carbon emissions.