UPS How does an Uninterruptible Power Supply work?

The UPS, or Uninterruptible Power Supply, works as a critical element to guarantee numerous services in our daily lives.

We live in a hyperconnected world that demands the immediate and uninterrupted availability of countless services. In our daily lives, thousands of elements, whose existence and function many of us are unaware of, intervene so that every gear in our society always functions perfectly. The discomfort it generates us every time communication networks or electricity fails is undeniable. For this reason, and despite the fact that technological investment in telecommunications infrastructure and electrical grids is leading to a very significant advance in service guarantees across all geographies, it is essential to have backup or emergency devices to avoid damage in the event of an unexpected interruption. One of these elements, which we are going to discuss today, is the UPS or Uninterruptible Power Supply, also widely known by its acronym in English UPS (Uninterruptible Power Supply).

These devices are present in places as diverse as data centers, hospitals, office buildings, industries, transportation infrastructure such as ships, or any other location that requires reliable, high-quality power supply that is available at all times. They are responsible for ensuring the continuity of electrical service when the grid experiences a failure or interruption of some kind.

In effect, the UPS is a backup so that, in the event of a power outage, the services of our systems do not fail, since they are devices capable of providing electrical power to other equipment through their batteries without having to depend on a network. The autonomy time of the UPS is determined by the type and number of batteries that the system has. The more batteries, the longer the network outage we can withstand.

Thus, an Uninterruptible Power Supply ensures that, for example, the energy needed by an operating room for a critical operation remains stable at all times; that the data centers that allow the internet connection to reach our homes do not cease their activity if there is a power surge due to an electrical storm; or that a ship’s communication systems do not suffer a failure, endangering maritime traffic, due to a critical power supply error. Perhaps now you are a little more aware of the importance of these unknown devices.

UPS or Uninterruptible Power Supply

In addition, a UPS works as a filter for those electrical systems or devices connected to the electrical grid. That is, if we connect one of these Uninterruptible Power Supplies to a ship, for example, we would protect all of that computer equipment from possible power surges or spikes, interference, frequency variations, or micro-cuts; the UPS’s action would filter all of this, achieving a perfectly clean output sine wave. This guarantees not only the proper functioning of the equipment connected to the network, but also its longevity.

Uninterruptible Power Supply How does a UPS work?

To understand how these elements work, it is first necessary to know the components that make up a UPS. Let’s see:

Elements of a UPS

• Rectifier/Charger: It is responsible for converting the electricity from Alternating Current, which arrives through the network, to Direct Current, either to charge the batteries or to power the Inverter.
• Batteries: They provide the necessary electrical energy to power the system in the event of a power outage.
• Inverter: This is an element that converts electricity – whether from the rectifier or from batteries – from Direct Current to Alternating Current, to be distributed to the systems connected to the UPS.
• Static and maintenance bypass: This is the type of electrical circuit that the UPS contains and allows the load to be connected directly to the main network (or an independent one) when the UPS fails.
• Control unit: This is the intelligent element that the Uninterruptible Power Supply is equipped with. Depending on the type of device and its functions, it will allow a series of functionalities via software or others.

What would be its normal operation?

When the UPS is operating normally, that is, with an available and quality electrical network, the electricity enters through the connection of the UPS to the electrical network and passes, in the first instance, through the rectifier, which converts the electricity from alternating current to direct current.

This transformation is necessary since part of the electricity must be able to be stored in the battery – for which it is necessary that the current is direct – the rest of the electricity continues its way to the inverter, which returns it to alternating current to power the systems that we have connected to the UPS.

What happens when there is a failure in the network?

Imagine that the electrical network is no longer available or that it is detected that the voltage is not within permissible quality limits; changing the current flow. In that case, the inverter would be powered through the direct voltage provided by the batteries. The inverter output would remain unchanged, and therefore the load connected to the system would continue to operate uninterrupted.

The runtime, or time during which the batteries can supply the system, will depend on the consumption required by the load powered by the equipment and the battery capacity. When the main supply voltage is restored, that is, reaches a value within the permitted tolerances, the rectifier starts working again and normal operation is restored.

The batteries recover from the discharge suffered during the absence of the grid, recharging through the direct current voltage supplied by the rectifier/charger.

What if there is a fault in the UPS or we need to perform maintenance tasks?

If there were a fault in the UPS, the Static Bypass would be automatically activated, whose function is to instantly transfer the load to the main supply network (or bypass) when an overload or short circuit occurs. Thus, regardless of their operation, UPSs guarantee that there is no interruption in the power supply to the load. Hence their name.

There are different circuits or types of UPSs that contain more or less elements, either protection or filters, to guarantee “clean” electricity; but they all contain at least the elements we’ve mentioned. For its correct operation, the most advanced UPSs have control units and software that offer real-time information to the user, as well as customized functionalities.

Supsonik, 35 years of experience in power electronics