What is a Uniterruptible Power Supply?

Uniterruptible Power Supply

A Uniterruptible Power Supply is a piece of equipment that is used to provide power to electrical devices such as computers or laptops in the event that the power supply is interrupted. It can be installed on-line or off-line.


The history of the uninterruptible power supply is a fascinating one. Its origins lie in the early days of railroads, where an impromptu power outage could cause catastrophic damage to equipment and passengers alike. In 1934, the United States Army awarded a patent for a device that would help ensure the safe operation of a locomotive. At the time, the idea was considered the magic bullet, but the technology was still in its infancy.

Uninterruptible power supply systems have come a long way since their heyday. Nowadays, there are portable models that can maintain a steady supply of power in a pinch. For instance, in 2003, the 46-megawatt Battery Electric Storage System in Fairbanks, Alaska, was turned on for the first time and began powering the city and surrounding rural communities during outages.

Aside from the aforementioned battery-backed AC power, these devices can handle temperatures as high as 50 deg C and can be DIN rail mountable. Some models also have networking capabilities and the ability to be used as part of a whole-building energy solution. They are globally certified and come in various sizes to suit the needs of any application.

Of course, the most important function of an uninterruptible power supply is to provide a means of backup power in the event of a catastrophic outage. Besides, such a device can improve the quality of electricity by supplying it in a safer and more efficient manner.

On-line vs off-line

When considering which type of UPS is right for you, it’s important to understand the differences between On-line and Off-line units. Understanding the difference is crucial to protecting your critical equipment.

Offline UPSs supply power directly from the mains to the load. They’re the best choice for personal computers and sensitive equipment. Their battery backup provides continuity in the event of a power outage.

In contrast, Online UPSs are fixed in line with AC mains and draw current from a battery. The inverter then regenerates a sine wave, supplying clean, uninterrupted power.

Unlike offline UPSs, online systems do not require an inverter, but they do require lost power sensing circuitry. Because they draw current from the battery, it’s important to have an efficient capacity to handle the load.

Both types of UPSs have the ability to provide uninterruptible power, but they’re designed to be used in different ways. While some of the more advanced systems feature double-conversion technology, others are optimized for simple one or two user PC installations. So it’s important to weigh your requirements against your budget.

Ultimately, the right UPS for your needs depends on how many devices you’re running and how long you’ll be running them. A system with high reliability, total harmonic distortion, and low maintenance costs is ideal.

Watts on a UPS

It’s important to know the Watts on a UPS because these are the numbers that help you to calculate how much power your UPS will be able to handle. If you don’t know how to find these numbers, you can get an estimate by consulting the manufacturer’s documentation.

The most common way to determine a UPS’s watts is by looking at its volt-ampere (VA) rating. To do this, you multiply the volt-ampere rating by the amperage of the device you are using.

As a result, some users will configure their systems based on the VA ratings. This can cause problems because if the VA and watts are not equal, the total load on the UPS will exceed its rated capacity.

Most larger UPS systems have a kVA rating as well as a Watts on a UPS rating. These are typically equal. However, some UPS manufacturers use a different formula to determine watts.

A typical kVA rating on a UPS is 100 kVA, and a kW rating is 125 kVA. If you have a planned 80 kW load, a 1.0 PF UPS should be sufficient.

You can find the maximum wattage on a UPS on its label or the owner’s manual. Some devices have a “controlled” outlet that allows you to turn off peripherals automatically, saving you from flicking switches.