What is the customer of a UPS-system looking for? To put it simply: a reliable and inexpensive system. The trouble is that it is not so easy to separate the wheat from the chaff – even for a specialist. If you look at the glossy brochures and movies of the various manufacturers of UPS (almost) all of them offer (almost) perfect modular UPS-systems. The ultimate seems to have been reached. The systems can be extended at any time, they are highly available and their efficiency can hardly be surpassed. In short, one wonders whether these firms have closed their research departments, because the perfect solution has been found. That this is not the case is demonstrated in this article.

Reliability and system availability
Everyone knows the indicator of reliability: MTBF (mean time between failures). The average working life of all the components of a system is used to calculate a figure for the life span of the entire system. But such figures have to be used with utmost caution, in other words they are not helpful in building confidence. What good is it, to be frank, if the MTBF formula works out a life expectancy of 250’000 hours, when the real problem lies somewhere else? Have all the components been assembled carefully? Will none of them get too hot during peak output? Is the entire modular system completely redundant in order to provide the stated availability? Granted, a breakdown rarely occurs nowadays, but if it does how long will it take until a specialist is at hand who will find out the real problem and come up with a solution?
Here is the crux of the matter. Does the manufacturing company employ UPS specialists with years of experience? Are spare parts quickly available? Without a replacement unit on site, probably not. All too often only the sales department works efficiently. Buying a UPS-system is somewhat like taking out an insurance policy. You have to look carefully at the small print!
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In the case of an emergency a DPA-module (40kVA) can be replaced within minutes by one person without taking the load off.

Modular technology
Exacting IT system managers have quickly recognised the advantages of modular UPS-systems. You pay as you grow. Indeed, from the point of view of investment it does not make sense to buy an oversized UPS-unit and operate it for years. The unit will produce waste energy in two ways: once within the UPS and then also in the air conditioning. Innovative companies grow, especially in the initial few years, but they may lack investment capital. Yet their power supply should grow simultaneously and continually. The solution lies in modular technology. Newave is one of the first to recognize this and has developed the Conceptpower DPA™ (Decentralized Parallel Architecture) UPS-system, which allows for expansion as the firm grows. Up to five modules can be accommodated in a rack with a footprint of 0.6 m2 each having an output of 40 kVA. In this way a power density of 200 kVA on 0.6 m2 of floor space is reached, a peak value, possible because of the extremely high efficiency (up to 96%) of Newave’s modules.

In such a set-up the battery packs are placed separately, which makes sense, because the cooler the batteries are stored, the longer they keep. And with regard to the service: in an emergency someone can replace a 40 kVA module within minutes without removing the load (hot swap). The power supply of your enterprise will not be affected during the operation.

In the power range of 10-1500 kVA Newave is the only manufacturer who is able to offer a third generation of UPS. Its market share with regard to modular systems is probably 10%. The production of highly compacted modular UPS-systems has been made possible through modern semiconductors (IGBT) and a design without a transformer. Newave is the inventor. Only after a significant reduction of size and weight was it possible to reach a power density that is shared by few other producers.

Another, perhaps even more important advantage of Conceptpower DPA™ is that the system can be made redundant without great effort or expense without having to increase the power of the whole system by factors two or three. An example illustrates this. A large IT company has a power requirement of 100 kVA. In order to create redundancy in the area of the UPS power supply, two traditional 120 kVA stand-alone systems could be installed to work in parallel, but this would by no means be an ideal solution. A far better solution would be the installation of 4 x 40 kVA modules, one of which would provide true redundancy. In such a set-up, several benefits can be noted. The 4 Conceptpower modules DPA™ work at 63% of the rated power of 160 kVA. At this level of power output the system still works with almost maximum efficiency. In a set-up where two systems of 120 kVA operate in parallel, the load factor is 41% i.e. the efficiency is much lower. For many UPS on the market the rate of efficiency is really low when they operate at 41% of the rated power. For Newave equipment it is still surprisingly high.

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The main technical data of the DPA^TM product-line are among the best world-wide.

Another advantage of modular technology is that a system expansion is achieved in a matter of minutes, simply by adding a module. You push the module into the rack while the system is operating, and that is all you have to do. The cost of the upgrade is limited to the cost of the module. The cost will, of course, be higher if a new rack is needed. The Conceptpower DPA™ system does not only allow a very simple way of expanding your UPS-installation, but also of replacing a damaged or faulty module.

Most modular systems on the market show very similar advantages – at least at first glance. But with regard to the architecture and the functionality there are significant differences and these should be of interest to specialists as well as investors. Too often, modularity exists only on paper. If only parts of a UPS-system are built in a modular way, then we cannot honestly speak of modular technology. Partial solutions in modularization offer hardly any advantage over conventional technology if you study them carefully – which brings us to the important topic of redundancy.

Redundancy
An overworked term. The number of redundancy principles probably corresponds to the number of suppliers of UPS-systems. Be that as it may, many UPS manufacturers clearly ‘fall through the mesh’ regarding genuine redundancy. A partial redundancy is ultimately no redundancy! If one component can cause a power breakdown there is no real redundancy. Typical single points of failure are: only one rectifier, only one inverter, only one static bypass, only one battery pack or only one control unit.

Operators of critical applications such as data centers, traffic control systems or sophisticated automation systems should check their future installations carefully regarding single points of failure, because the availability of power decides who is successful in gaining the ascendency. What then is genuine redundancy?