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Facility Maintenance Decisions

Understanding Backup Power, UPS Modules



Understanding applications can help managers ensure power system reliability.


By John Lutz   Power & Communication

OTHER PARTS OF THIS ARTICLEPt. 1: Understanding Backup Power, Generator ApplicationsPt. 2: This PagePt. 3: Understanding Backup Power, Effective TestingPt. 4: SIDEBAR: Backup Basics-Testing, Testing
Understanding Backup Power, UPS ModulesDeveloping a high level of confidence in an electrical infrastructure can lead to a stronger sense of system ownership and trust that it will respond as designed.

UPS modules

UPS modules protect facility loads, not only in the event of a loss of incoming power but also if that incoming power falls outside of acceptable limits. In a typical configuration, redundant UPS systems provide power to critical loads. Two or more UPS modules support the total load of a single module, thus allowing that module to maintain all critical loads in case of failure.

The typical application involves the use of a double-conversion module backed up by a battery, but managers can use alternative sources, such as flywheels, which come with substantial sticker and maintenance costs. To increase redundancy and critical power capacity, multiple UPS modules can operate in parallel. This application typically is accompanied by a distributed static-bypass system.

The typical UPS module operates in three modes: normal, or on inverter with battery backup; internal static bypass, operating on an internal static switch with no battery backup; and external or maintenance bypass. The normal mode of UPS provides battery power to the load in case of an interruption to the incoming power supply. While operating in both internal or external bypass mode, there is no battery backup and, thus, the continuity of power to the load is interrupted during a loss of incoming power.

Eye on energy

In typical applications, the emergency generator operates on standby. But in some advanced configurations and designs, generators can supplement incoming power and reduce power consumption, which is known as peak shaving. While this does not have a direct correlation to efficient energy use, using the backup generation system to offset utility consumption can curtail energy costs.

Even with a generator that is shut down, managers can improve energy efficiency by assessing the auxiliary support systems that are always online. By effectively sizing and specifying these systems and properly maintaining them, managers can reduce waste and unnecessary costs.

Generators with alternative fuel sources — LP gas, for instance — also can increase energy efficiency and lower energy costs. But in some cases, alternative fuel sources also require additional support systems and hardware, which can lead to a higher overall energy use when the generator is in automatic standby.

On the other hand, specifying and operating UPS systems with energy efficiency in mind — especially where 24/7 operation is required — can produce considerable savings. UPS efficiency at all load levels is a key selling point, even for simpler systems. While most UPS systems operate at relatively low load compared to capacity, specifying and selecting units that have high efficiencies at lower load levels can reduce energy waste.

Modes of operation available in newer UPS applications can reduce steady-state energy use even further. For some managers, using these applications can introduce an additional layer of risk, but thoroughly testing these applications can lead to increased confidence and comfort with their implementation.


posted on 6/20/2017

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