What Is an Uninterruptible Power Supply?

Uniterruptible Power Supply

Uninterruptible Power Supply (UPS) systems provide emergency backup power in case of a power loss. This allows for orderly shutdowns of equipment to avoid damage or data loss.

There are three basic topographies for UPS systems: offline/standby, double-conversion, and line-interactive. Most UPS lines below 1 kilovolt-ampere (1 kVA) are of the line-interactive type and usually less expensive.

How It Works

UPS devices protect your devices from sudden power surges, blackouts and power failures. Without a UPS, your business could lose critical data, miss opportunities and suffer equipment damage. Today, business owners rely on UPS systems to safeguard their computer setups, server rooms and other hardware arrays against expensive power outages that occur on a daily basis.

Basically, UPS devices work by storing energy for a short amount of time and then seamlessly transitioning to battery power if utility power fails. This window of time enables you to save data, exit properly and shut down the device in a controlled manner without risking the integrity of your hard drives or files.

There are several different UPS topologies available to meet the needs of different applications and environments. However, all UPS systems deliver near-instantaneous protection from input power failures using the energy stored in batteries, supercapacitors or flywheels. There are four main functional components of a UPS: the battery, inverter, rectifier and static bypass switch.


Uninterruptible Power Supply technology was first invented in 1934 by John Hanley. He patented his device with the lofty name “Apparatus for Maintaining an Unfailing and Uninterrupted Supply of Electrical Energy.”

Hanley’s work was originally used to provide backup power for rail passenger trains in case of power surges or failures. He feared that rail systems without power could cause accidents and endanger passengers.

UPS technology has since evolved to support more applications and offer greater functionality including orderly shutdown, load shedding and battery maintenance. Today, there are three main types of UPS: online double-conversion, line-interactive and offline/standby.

In an online double-conversion UPS, the batteries are permanently connected to the inverter so they can instantly switch over to provide emergency power. The most advanced UPSs also filter and regulate mains/utility power, allowing for longer battery backup times. In contrast, offline/standby UPSs only provide backup power for a few seconds. However, they are cheaper and offer more basic features such as surge protection.


UPS systems function as an alternative source of power that can sustain computer use for a short time during a power outage. They can also keep your equipment running smoothly if you are experiencing a power surge that can damage sensitive electronics.

Basically, UPS systems regulate the power coming from the outlet to ensure that your computers receive a clean and stable voltage. It protects the system from harmful power surges and brownouts that can cause serious data loss, hardware failure, and other disruptions.

In fact, without UPS backup in place, businesses lose about $50 billion per year because of unexpected power interruptions. So, if you want to keep your business humming along smoothly and avoid potential loss and downtime, invest in a UPS system. It’s an investment that pays off in the long run. Just make sure you hire a professional to install your UPS system, as it requires some electrical work to get started.


The UPS system works on batteries and supercapacitors to store electrical energy. The on-battery run-time of most UPS devices is relatively short, providing enough power to perform a controlled shutdown of computer systems or other hardware before an outage occurs.

Typically, the UPS device receives utility power via a direct AC connection under normal operating conditions. The UPS system then uses a transformer to regulate the voltage and convert it to battery power.

This stored energy is then used to power devices in the event of a power surge or outage, providing an on-battery run-time varying by model and type for periods of time from minutes to hours.

Other UPS technologies include the flywheel rotary design that uses a high-speed flywheel to spin and build kinetic energy for backup power for up to 90 seconds. Line-interactive UPS models use inverter/converter technology that can automatically regulate the voltage, supporting equipment during fluctuations as well as outages.