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UPS Basics: How does a UPS work?

Tue 3 Jul 2018


Data centre power management specialist Riello UPS explain everything you’ve ever needed to know about the various types of uninterruptible power supplies.

In our previous ‘UPS Basics’ videos, we’ve covered relatively straightforward questions such as How is electricity generated? and What are the most common power problems? This week we turn our focus to something a little more technical.

As data centre operators you know just how important an uninterruptible power supply (UPS) is in minimising downtime and data loss. It’s your first and foremost line of defence against any disruption to the mains supply. And if the worst ever happens and the power goes down, a robust and reliable UPS unit gives your servers and IT equipment those crucial few moments to safely shut down without wiping data.

But do you know how a UPS works? And more importantly, what are the different types of UPS unit, and which might be the most suitable for your data centre?

This brief yet entertaining animation outlines the three main types of UPS:

Offline UPS – also known as Voltage and Frequency Dependent (VFD). This is the simplest and least-expensive form of power protection. The load is always supplied by the mains, and in the event of a power outage, the system switches to the UPS and its fully-charged batteries as a backup. For mission-critical environments such as a data centre, an offline UPS isn’t likely to be the most appropriate method of power protection.

Line-Interactive UPS – also known as Voltage Independent (VI). This style is similar to an offline UPS, but with the added protection of an automatic voltage stabiliser or AVS. This minimises the risk of experiencing any unpredictability in voltage. Line-Interactive UPS units are typically used in telephone switches, servers, and smaller motor applications.

Online UPS – also known as Voltage and Frequency Independent (VFI), as well as double conversion. In this type of power protection system, the load isn’t directly connected to the mains. Power enters the UPS and travels through a rectifier that converts it from alternating current (AC) to direct current (DC). The UPS inverter then converts it back to AC before powering the actual load. Unlike both methods mentioned previously, if there’s a mains failure or disturbance in an online power protection system there’s no break in power – even for a few milliseconds – while it instantly switches to backup supply.

Watch the video to learn more about the different versions of uninterruptible power supplies and how a UPS works:

Coming up next week in the penultimate ‘UPS Basics’ video, get the lowdown on all the different types of UPS operating modes and how to utilise them to optimise your data centre’s power protection performance.


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