Data centers require power, in a stable and continuous supply, and it must be controlled carefully. Incoming fluctuations such as voltage dips or surges can damage sensitive electronic equipment, and power outages result in costly downtime. These hazards can be prevented with the use of uninterruptible power supply (UPS) systems. A UPS regulates the flow of power and, in the event of an outage, provides battery backup so operations can continue with little to no disruption. Battery power will last long enough to either shut down equipment safely or activate an alternative source such as a generator.<\/p>\n
There are three main types of uninterruptible power supply systems, defined by how power moves through the unit:<\/p>\n
1. Standby<\/strong><\/p>\n In a standby or off-line system, the AC input is filtered through the unit and past the transfer switch at the output point. When an input failure occurs, the battery and the inverter (which converts the battery\u2019s DC power to AC) are activated and feed the output. These uninterruptible power supply systems are relatively low-cost and efficient, work best in applications under 2kVA, and are frequently used for personal computers and workstations.<\/p>\n There are some subcategories. Standby-Ferro systems add a special \u201cFerro-resonant\u201d transformer to help regulate voltage. This once-popular design for mid-range UPSs has fallen out of favor because of low efficiency and instability issues. Many uninterruptible power supply systems below 10kVA that are designated as on-line are actually standby on-line hybrids, since the inverter is on-line but the DC\/DC converter from the battery is in standby.<\/p>\n 2. \u00a0Line-Interactive<\/strong><\/p>\n With line-interactive uninterruptible power supply systems, the inverter becomes part of the output and is always on. The inverter can operate in reverse to charge the battery while AC input is normal, and switch to battery power when input fails. This design provides increased filtering and voltage regulation. This highly reliable and efficient system is well-suited for small business, Web, and departmental servers, though it becomes impractical in applications over 5kVA.<\/p>\n 3. On-Line<\/strong><\/p>\n For higher voltage applications, an online UPS is best. In an online system, the inverter is the primary power path instead of the AC input. There are two major types of online uninterruptible power supply systems:<\/p>\n\n