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Modular UPS (uninterruptible power supplies) - January 2012

Published by Jason Koffler on 13 January 2012

How can you address your needs, in terms of UPS power protection, of today and tomorrow without grossly over-sizing your system and running inefficiently?

It’s a question many DCMs (data centre managers) and other UPS customers have pondered for years. For DCMs in particular, pinpointing how much and how quickly requirements will grow as the business expands and more equipment is brought in is almost impossible.

Running UPS at (or close to) full capacity is not recommended for mission-critical application as it leaves no room for the system to cope with overloads. Also, in a parallel-redundant UPS system with an N+1 configuration, each single UPS module must be sized so as to be able to take over the total load if its parallel partner goes offline or out of service for whatever reason. In essence, each module will only ever be operating at a maximum 50% load, which is inefficient.

In order to address the need for high UPS efficiency and scalability, UPS manufacturers have introduced Modular UPS, which enables UPS redundancy to be built in and UPS capacity to be increased in smaller, incremental steps.

Comprised of individual units of 15kVA; up to eight of which can be connected together in cabinet (much like a server rack cabinet) that utilises a ‘drawer-style’ approach to offer a maximum (per cabinet) of 120kVA. Each unit is a fully functioning UPS in its own right; there are no shared components. Units can be easily slid out and ‘hot-swapped’ for maintenance or repair and this can be done offsite, which greatly reduce MTTR (meantime to repair). Either a user can do it within minutes; or an engineer can complete the process within a couple of hours as opposed to the traditional 24 hours or more it may take to successfully execute a repair onsite.

Other benefits of modular UPS:

Decreased use of floor space.

Floor space in data centres, in particular, comes at a premium and is usually reserved for revenue-earning equipment, such as servers. Modular UPS is based on a rack-type, stacked enclosure with battery storage in the base. A 120kVA modular UPS rack (comprised of eight 15kVA units) takes up 25% less floor space than a 120kVA standard UPS unit.

High availability.

Availability of a UPS system is defined as the percentage of time that it can deliver condition power. Because of their low MTTR (as explained above) modular UPS offer high availability in comparison to other UPS designs.

High efficiency.

It is possible to operate modular UPS systems at much higher load capacity and still achieve redundancy making it an extremely efficient option.

Modular UPS is not suitable for all applications but when it is, it offers some exceptional advantages and should be considered. It can also be incorporated into a total power protection system, alongside traditional UPS. Some users have incorporated traditional UPS as their primary source of protected power with modular systems as a secondary source for their most critical, dual corded hardware to provide highly efficient and cost-effective 2N redundancy.