How Does an Uninterruptible Power Supply Work?

by Keith Evans

UPS Works on Commercial Power

An Uninterruptible Power Supply (UPS), works by drawing power from a commercial power source. Because the UPS does not actually generate its own electricity, it must receive electrical input from an outside source like a generator or electrical outlet. Under normal operation, the UPS simply serves as a pass-through device, accepting electrical input from an outside power source and providing electricity to devices plugged in to the two, four, six, or more electrical outlets on the UPS device itself. While this configuration is typical and how the UPS operates most of the time, its true function is served when the outside power source becomes unavailable.

UPS Devices Are Batteries

Under normal operation, uninterruptible power supply devices accept input from commercial power sources and provide pass-through electricity to devices plugged into outlets on the UPS device itself. As the UPS accepts incoming electricity, though, it quietly charges its own internal batteries for use at a later time. If (or when) the commercial power supply fails, the fully charged batteries inside the UPS housing continue providing electricity to the connected devices. Depending on the size and type of the UPS and the number of devices plugged in to it, the uninterruptible power supply batteries may continue providing electricity for several minutes or even up to a few hours. As the electricity stored in the batteries (which, in electrical terms, are known to technicians as capacitors) depletes, the electrical output expires and the devices lose power. Most UPS devices provide ample time, though, for users to safely shut down sensitive electronics or computers under UPS power should commercial power fail.

Some UPS Devices Use Software

While the standard operation of uninterruptible power supplies is to provide electricity when commercial power becomes unavailable, some UPS devices offer additional services designed to save attached computer equipment. When power fails to these devices, which contain a microprocessor and specialized software, the UPS device sends a "shut down" signal to any attached and configured computers. The shut down procedure saves any open documents, stores sensitive system files in their appropriate location and turns off the computer. By using Ethernet, serial or parallel connections to communicate with attached and configured computers, advanced UPS devices can reduce the likelihood that important data may be lost in the event of a commercial power failure.

About the Author

Keith Evans has been writing professionally since 1994 and now works from his office outside of Orlando. He has written for various print and online publications and wrote the book, "Appearances: The Art of Class." Evans holds a Bachelor of Arts in organizational communication from Rollins College and is pursuing a Master of Business Administration in strategic leadership from Andrew Jackson University.