Every day, interruptions to electrical service in homes, businesses, and public sector organizations occur. The losses from these power outages can be extensive and of great consequence. For a business, the recovery time is significant and the costs are high. According to PricewaterhouseCoopers research, after a power outage disrupts IT systems:
Power outages can cause substantial losses for the companies affected. According to the U.S. Department of Energy, when a power failure disrupts IT systems:
Why a UPS? A UPS protects IT equipment and other electrical loads from problems that plague our electrical supply, performing the following three basic functions:
UPS Topologies There are several different UPS topologies that provide varying degrees of protection. Selecting the best fit depends on several factors, including the level of reliability and availability desired, the type of equipment being protected, and the application/environment. While all four of the most common UPS topologies outlined below meet the input voltage requirements for IT equipment, there are key differences in how the result is achieved, as well as the frequency and duration of demands on the battery.
Standby UPSs allow equipment to run off utility power until the UPS detects a problem at which point it switches to battery power to protect against sags, surges or outages. This topology is best suited for applications requiring simple backup such as small office/home office and point-of-sale equipment.
Online UPSs provide the highest level of protection by isolating equipment from raw utility power –converting power from AC to DC and back to AC. Unlike other topologies, double conversion provides zero transfer time to battery for sensitive equipment. This topology is best applied to mission-critical equipment and locations where power generally is poor.
Line-interactive UPSs actively regulate voltage either by boosting or decreasing utility power as necessary before allowing it to pass to the protected equipment or by resorting to battery power. Line-interactive models are ideal for applications were protection from power anomalies is required, but the utility power is relatively clean. MDF and IDF communication closets, non-centralized server and network rooms, and general IT enclosures are ideally suited for this topology.
Ferroresonant UPSs operate similarly to line-interactive models with the exception that a ferroresonant transformer is used to condition the output and hold energy long enough to cover the time between switching from line power to battery power, which effectively means a no-break transfer. Many ferroresonant UPSs are 82-88% efficient and offer excellent isolation. Although no longer the dominant type of UPS, these robust units are still used in industrial settings, such as the oil and gas, petrochemical, chemical, utility, and heavy industry markets.