A computer expects to receive 120 V of AC power, oscillating at 60 Hz from the average American outlet. The average computer can tolerate slight differences from this specification, but any significant deviation will cause the computer's power supply to fail. A Uninterruptable Power Supply (UPS) usually protects a computer against four common problems:

    1. voltage surges and spikes—when the voltage on the line is greater than it should be
    2. voltage sags—when there is power on the line but the voltage is less than it should be
    3. total power failure—when total power is lost
    4. frequency differences—when power oscillates at something other than 60 Hz

There are two common systems of Uninterruptable Power Supply in use today—standby and continuous UPSs.

A standby UPS runs the computer off of the normal utility power until it detects a problem. At that point, it quickly (in 5 ms or less) turns on a power inverter and runs the computer off of the UPS's battery. A power inverter simply turns the DC power delivered by the battery into 120 V of AC power, oscillating at 60 Hz.

A continuous UPS is constantly running the computer off of a battery. A powerful charger is continuously recharging the battery. The battery charger continuously produces DC power. The DC power is being inverted into 120 V of AC power. If the power fails, the battery provides power to the inverter and the computer keeps running. There is no switch-over time in a continuous UPS. This setup provides a stable source of power.

Standby UPSs are far more common for home or small business use. They tend to cost about half as much as a continuous system. Continuous systems provide extremely clean, stable power, so they tend to be used in server rooms and mission critical applications.

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JetCafe

This page by JetCafe is a basic overview of what Uninterruptable Power Supplies are. It contains information about what a UPS is, how it works, how to determine the size of the UPS you should use, and other helpful information. If you want to learn more about what a UPS does and how it might be beneficial to you, this is a good page to visit.

UPS INFORMATION

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UPS Systems

UPS Systems has provided us with a wonderful page that contains all the information you need when investigating Uninterruptable Power Supplies. Their page is framed so I was prevented from linking each of their pages to this one. So, I will just give you quick overview of what is on this page.

UPS Systems has a page that contains links that are designed to help the user learn more about UPS systems. This page has three links: UPS Design Types, How software can help, and Remote Monitoring. The Ups design page goes over the four styles of UPSs. The software page talks about software that will automatically shut down your computer when the UPS voltage becomes low. And the remote monitoring page explains about the ways to remotely monitor your UPS.

The other page that I found useful on this site was the FAQ page. It had a lot of great questions with easy to understand answers. They also have a page that contains UPS manufacture links.

UPS Systems