Uninterruptible Power Source (UPS)
What is an Uninterruptible Power Supply?
An uninterruptible power supply or a UPS system is an electrical apparatus that provides emergency power to a load when the input power source or mains power fails. A UPS system performs three primary functions: conditions the incoming dirty power from the utility company to give you clean, uninterruptible power, provides ride-through power to cover for sags or short-term outages, and enables seamless system shutdown during a complete power outage..
What is the difference between single-phase UPSs vs. three-phase UPSs vs. split-phase UPSs?
Phases of a UPS, such as a single-phase UPS or a three-phase UPS, describe the number of electrical phases that a UPS receives and transmits. Electrical utilities generate three-phase power because that is the most efficient way to transport electricity over long distances. And for larger power consumers, such as large data centers, industrial manufacturing and hospitals, the power stays as three-phase, requiring a three-phase UPS. For smaller power consumers, including residential or office buildings and most K-12 schools, the power is converted to single-phase power.
Some applications contain a mix of single-phase and three-phase equipment and require a UPS that can protect both. For those deployments, a split-phase UPS, which can simultaneously provide 120V and 208V output, is often the best option.
What size UPS do you need?
UPSs are given a power rating in volt-amperes (VA) that range from 300 VA to 5,000 kVA. This rating represents the maximum load that a UPS can support, but it shouldn’t match exactly the power load you have. To allow room for growth, the best practice is to choose a UPS with a VA rating that is 1.2x the total load you need it to support. If your UPS will be supporting motors, variable-speed drives, medical imaging devices or laser printers, add more VA capacity to your requirements to account for the high power inrush that occurs when those devices startup.
Companies that are anticipating rapid growth should use a higher multiplier than 1.2x. Newer server hardware tends to have higher power requirements than older models, so factoring in additional VA will account for adding more and newer equipment.
What are the different types of UPSs?
UPS systems are grouped by topology, which refers to how the UPS and utility power work together. This translates to the level of efficiency and reliability you can expect from your power source. There are five main types of UPS topologies:
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 or with less sensitive equipment, such as small office/home office and point-of-sale equipment.
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 where protection from power anomalies is required, but the utility power is relatively clean. Main distribution frame (MDF) and intermediate distribution frame (IDF) communication closets, non-centralized server and network rooms, and general IT enclosures are ideally suited for this topology.
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, this double conversion method provides zero transfer time to battery for sensitive equipment since the electricity is already coming from the UPS. The online, double conversion UPS topology is best applied to mission-critical equipment and locations where utility power is poor or highly unreliable.
Ferro resonant UPSs operate similarly to line-interactive UPSs with the exception that a ferro resonant 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 ferro resonant UPSs are 82-88 percent 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.
Multi-mode UPSs are considered the best choice for companies looking to achieve an optimal balance of efficiency and protection. The two modes within these UPSs are a high-efficiency, eco-mode and a premium power protection mode. The UPS can switch between these two modes automatically when it detects problems in the utility power. This functionality can save a significant amount in operating expenses.