An uninterruptible power supply (UPS) is a device that, thanks to its batteries or other energy storage elements, during a power outage can provide electrical energy for a limited time to all the devices it has connected.[1]​ Another function that can be added to this equipment is to improve the quality of the electrical energy that reaches the loads, filtering voltage rises and falls and eliminating harmonics from the network if alternating current is used.

UPS provide electrical energy to equipment called critical loads, such as medical, industrial or IT devices that require permanent, quality power, to always be operational and without failures (voltage spikes or drops).

The unit of power to configure an uninterruptible power supply system is the volt-ampere (VA), which is the apparent power, or the watt (W), which is the active power, also called effective or effective power, consumed by the system. To calculate how much energy a UPS requires, you must know its consumption. If what is known is the effective or effective power, in watts, the number of watts is multiplied by 1.4 to take into account the maximum peak power that the equipment can reach. For example: (200 W × 1.4) = 280 VA. If what you find is the nominal voltage and current, to calculate the apparent power (VA) you must multiply the current (amperes) by the voltage (volts), for example: (3 amps × 220 volts) = 660 VA.

DC UPS

The loads connected to the UPS require a direct current supply. Therefore, these will transform the alternating current from the commercial grid into direct current, and use it to power the load and store it in their batteries. Therefore, they do not need converters between the batteries and the loads.

There are mainly 3 types of UPS. Each corrects different common power interruptions:.

The role of uninterruptible power supply systems is to supply electrical power in times of supply failure, in a “short” time interval (if it is a failure in the network supply, until the isolated emergency systems begin to operate). However, many UPSs are capable of correcting other supply failures:

Typically, UPS manufacturers classify equipment based on the electrical faults they correct. You can obtain a voltage regulator that, in addition to avoiding electrical overloads, keeps the equipment running for several minutes in the event of a power outage.