What Is an Uninterruptible Power Supply (UPS)?

What Is An Uninterruptible Power Supply (UPS)?

By: marysmith

An uninterruptible power supply (UPS) is a piece of equipment that powers your computer or other electrical appliances to keep them running for a while in the event of a power cut. At the same time, UPS devices protect computers and equipment  in the comms room from power surges.

The main element of a UPS is a battery that starts running as soon as the device detects that the primary power source has stopped working. If someone is working on their computer by the time they get the UPS notification of a power cut , they have enough time to save their work and to exit before the battery runs out. The biggest problem with computers is that in the event of a power cut, their random access memory (RAM) is erased. This is the reason why you lose your unsaved work, and this is what a UPS prevents from occurring. At the same time, should a power surge occur, the UPS detects and regulates it before it has the chance to affect your computer.

Data Centres And UPS Devices

UPS devices convert incoming AC to DC, and then convert it back via an inverter. In-built batteries store energy to release in the event of a power source failure. Thanks to the bypass circuit, you can run the IT equipment connected to the network on either utility mains or generator power.

Generators are different from UPS devices. The main difference is that they can’t power devices once the primary source is cut. Nevertheless, generators can supply power for a much longer period of time than UPS systems. As UPS devices are powered by batteries, they can’t last for too long.

UPS systems are also known as double-conversion devices, line-interactive or standby designs. However, these alternative terms haven’t been consistently used, so manufacturers interpreted them their own way. The International ElectroTechnical Commission (IEC) published a standardised technical terminology in order to bring some clarity into this matter and to help consumers and manufacturers find their way through this descriptive terminology.

A Type Of UPS Device And Its Main Features

Voltage and frequency independent (VFI): These systems are also known as dual or double conversion sources, the reason being that AC is transformed into DC to keep batteries charged at all time and to drive the inverter. The inverter transforms DC into AC power that keeps IT equipment running.

In the event of a power cut, the batteries drive the inverter. The inverter goes on with its task of allowing the IT load to run. When the power from their main source is restored, the rectifier supplies DC to the inverter, while also charging the batteries. The inverter never stops. Utility input has no connection to the output. The bypass is there only for maintenance safety reasons pr for the event of an internal electrical problem. This type of UPS system is considered as being the most robust and durable. It is also frequency independent, because it doesn’t need to synchronise the output and input frequencies (although some of these systems do).

Advantages And Drawbacks Of UPS


  • Instant switching from the main power source to the batteries.
  • Better support for critical instruments by comparison to generators.
  • Users can choose their ideal type and size of UPS.
  • They are silent.
  • Maintenance is fairly inexpensive.


  • They can’t run heavy appliances.
  • They may need professional setup and installation.
  • They may need frequent replacement of their batteries.
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