What is UPS Uninterruptible Power Supplies

types of ups

A UPS (Uninterruptible Power Supply) or uninterruptible power supply (UPS) is a device for automatically and uninterruptedly supplying electrical energy to electrical equipment connected to it. The presence of an uninterruptible power supply allows you to receive high-quality electric current even despite interruptions in the power supply system. With a complete power outage thanks to the UPS, you can save important data and correctly shut down the computer.

First of all, uninterruptible power supplies are used to connect computer equipment – the system unit and monitor, sometimes – an inkjet printer. It is not recommended to connect devices with high power consumption, such as a laser printer, to the UPS, since the UPS will most likely not withstand the load and turn itself off.


UPS (uninterruptible power supply) for the computer. What is it and how to choose?

uninterruptible power supply

UPS means Uninterruptible Power Supply (UPS) in English – Uninterruptible Power Supply (Source, Systems)). Literally, this means uninterrupted power supply.

A modern UPS is an electronic device equipped with a battery, an inverter, a voltage filtering unit, a controller connecting all the modules into a single controlled complex.

UPS is equipment that performs two main functions

UPS – protects against power surges and blackouts.

  • The first is to maintain the operation of electronic devices in the event of a sudden power outage.
    In other words, if the computer is connected to the UPS, it will not turn off when there is a sudden power outage.
  • The second function is to protect equipment in the event of a power surge.
    The UPS is a kind of buffer that protects electronic devices from any interference in the mains.

Why are these two features important?

What can happen if there is a sudden change in the quality of the power in the outlet?

If your computer shuts down suddenly, you may lose valuable data, open projects that do not have time to be saved in the computer’s memory.

At the same time, no data recovery will help – the project will be completely erased, as it was stored in the computer’s RAM, and not on the hard disk at the time of working with it.

Another problem is equipment failure. Electronic devices are sensitive to static electricity, as well as to voltage drops, even a few volts.

Therefore, for example, when assembling a computer (upgrading, repairing a computer), it is recommended to ground (touch something metallic, such as a radiator) or use an electrostatic tape before assembly.

A sudden power outage or power surge is much more dangerous than static. Motherboard, processor, hard drive may be damaged forever.

The correct voltage in the outlet should be about 230 V. Fluctuations and deviations from the norm are difficult to predict and can be caused, for example, by improper operation of the equipment at home.

Over-voltage i.e. A sudden power surge may be caused by a lightning strike in the area or a malfunction of technical equipment in your building.

Types of ups

UPS’s are divided into three types: on-line, off-line and line-interactive.
What is the difference?

  • The most modern solution is on-line power supply. It completely isolates the connected equipment from the input voltage. The AC voltage from the mains is converted to direct voltage, and then again to alternating voltage. Due to this, the output voltage is very stable and resistant to interference and overvoltage. An online power supply often requires additional cooling and is quite large.
  • A good basic equipment is an off-line emergency power supply. It does not convert current all the time, but reacts when it detects a change in input voltage. Then it turns off the power to the equipment and turns on the batteries. Provides good protection when a power outage occurs.
  • Line-interactive power supply is a more advanced version of the off-line power supply. An additional functionality is protection not only against voltage loss, but also from interference in the mains.

How to choose a UPS

First of all, you should pay attention to the following features:

  • Emergency power supply – manufacturers indicate total power (in volts-amperes, or VA) and effective power (in watts, or W), which is the actual power that you can use to power the equipment;
  • Waveform – in this case, the full or approximate sinusoidal waveform is the best solution;
  • Backup time – determines how long the UPS will be able to supply power to the equipment when there is no power in the outlets;
  • Switching time – this parameter refers to the time when the UPS should respond in the event of a power failure, interference detection, etc .; the shorter the time, the better, it should not exceed 10ms;
  • Number of outlets – it is not recommended to connect extension cords to the power supply, so consider how much equipment you will connect to the emergency power source.

The voltage in the outlets has a sinusoidal direction. The closer the sinusoidal waveform in the UPS to the waveform in outlets, the safer for devices connected to the UPS.
For each application, it is worth choosing power supplies with the following parameters:

  • Basic home applications – in this case (for example, connecting a computer to multimedia, household appliances), a stand-alone UPS with an effective power of 300 W or more, for example Ever DUO II 500, is suitable;
  • Protection of the gaming computer – gaming PCs consume more energy than multimedia, and their components are more valuable, so you should connect them to a line-interactive power source with an effective power of at least 500 watts, for example, Fideltronik ARES 1000;
  • UPS for the office – the choice depends on the quantity and type of connected equipment; for a small business, it may be sufficient to have the same UPS as for a home, such as the Easyline 650AVR USB. But, if you need to connect several devices (except computers, for example, projectors, multifunction devices, etc.) and a server, you must choose an online power source with a capacity of at least 800 watts.

Among other firmware, UPSs are used for this. Uninterruptible power supplies are so firmly entrenched in our computer life that the abbreviations UPS, UPS have long been no longer needed to be decrypted.

Most modern UPSs, in addition to their main task – to provide uninterrupted power – also filter the voltage supplied to the load (act as a network interference filter) and stabilize the voltage (act as a voltage stabilizer).

the objective of an uninterruptible power supply (UPS) is to provide electricity to equipment connected to the UPS (UPS) during a power outage.

Let’s take a closer look at what you need to pay attention to when choosing a UPS (UPS), what types of UPS (UPS) exist, what technical characteristics will play a major role in choosing.

There are three types of UPS:

  • off-line
  • line-interactive
  • on-line.

Off-line: the simplest UPS circuit (UPS) and therefore the cheapest.
The acquisition of such a UPS (UPS) is justified only if you do not have voltage fluctuations, but occasionally power is lost.
The principle of operation of this UPS (UPS) is very simple – when the voltage drops below the allowable input voltage limit of the UPS (UPS), the device switches to battery operation.

Tip: If you have voltage fluctuations in your network, it is best to purchase a UPS with a higher class (line-interactive). The fact is that with frequent fluctuations, an off-line class device will constantly switch to battery operation and back. And this will significantly reduce battery life.

Line-interactive: Compared to the off-line UPS (UPS), it uses a more complicated circuit. The output signal in line-interactive, in comparison with off-line, is more accurate (approximated sine wave). This type of UPS has a built-in voltage regulator.

Tip: When purchasing such a device, pay attention to the input voltage range, the larger it is, the better. A UPS with a wide input voltage range during voltage fluctuations will be less likely to switch to battery operation, and accordingly, the battery life will be longer.

On-line : This is a double conversion circuit, i.e. the input voltage is independent of the output voltage.
The principle of operation of the UPS (UPS) of this type is as follows: the alternating voltage that is supplied from the network, the UPS rectifier turns into a constant voltage, which charges the battery.

At the output there is an inverter, which turns a constant voltage into alternating voltage, supplying it to the load. UPSs of this type are more expensive, but protect against all power failures. The on-line output of the UPS is a pure sine wave.

What is UPS and how does it work

uninterruptible power supply how it works

Why do I need a UPS?
Uninterruptible power supply (UPS or UPS – Uninterruptible Power Supplies) is designed to supply the computer with electricity in the event of a power failure.

A sudden power outage is fraught with loss of data and physical damage to equipment.

In the electrical network there is always interference and surges that occur when switching powerful consumers.

If the load on a particular electric line is large, the voltage at the load decreases below normal. An uninterruptible power supply is also needed in order to supply computers (and other loads) with “clean” voltage.

In the event of a power failure, the source starts to work from the battery, producing an alternating voltage of 220 V for the computer.

How does the UPS work?

The constant voltage of the battery (usually 12 V or 24 V, if the batteries are connected in series) is converted into AC 220 V using a special device – a built-in inverter. If the voltage disappears, the uninterruptible power supply is usually accompanied by a light and sound indication to attract the user’s attention.

Depending on the battery capacity and load power, the UPS provides alternating voltage at its outputs for typically 5 to 20 minutes (except in special cases). This time is enough to close all applications (running programs) and turn off the computer.
All sources are divided into three large groups:

  • passive stand-by
  • linear interactive (line interactive),
  • with double conversion.

Passive UPS

The filter protects the output of the device and its electronics from voltage surges, which are often in the electrical network.

The AC voltage is rectified by the rectifier and (through the charger, which is not shown in the diagram) recharges the battery.

In normal mode, when the voltage level in the network does not exceed normal limits, the filtered mains voltage passes through the key to the UPS output connectors and supplies the load.

As soon as it goes beyond or disappears, the inverter starts working.

It turns the constant voltage from the battery into alternating voltage with the required amplitude, which is supplied to the load through the switch.

In this case, the battery can give off a sufficiently large current, since the load – for example, a computer with a monitor – can consume 200 watts or more. As soon as the input mains voltage is within the normal range, the controller turns off the inverter and supplies the filtered mains voltage to the UPS outputs.

If it is absent for a long time, the controller turns off the device, protecting the battery from deep discharge.

Line Interactive UPS

Line-interactive sources differ from passive ones, in particular, in that they include an autotransformer.

This allows you to work in a wider range of input mains voltage without switching to batteries. An autotransformer differs from a conventional transformer in that it contains not two (or more) galvanically isolated windings, but essentially one winding with taps.

If the input mains voltage is lowered for a long time, the controller, switching through the keys of the autotransformer winding, increases the voltage level at the output connectors of the UPS.

If the voltage is increased for a long time (within known limits, of course), the controller, switching the windings, lowers its level at the output connectors.

This technology is called AVR (Automatic Voltage Regulation).

The signal generated by the inverter can be in the form of an approximated (stepwise) sinusoid or in the form of almost rectangular pulses.

The latter is not as bad as you might expect.

Most modern power supplies, including computer ones, are pulsed, the mains voltage in them is still straightened first.

Double conversion UPS

The most advanced sources are those with double conversion, which are used in the most critical cases (for powering servers and equipment that are sensitive to network voltage parameters). In uninterruptible power supplies of the first two types, the frequency of the mains voltage at the output (in those cases when the inverter does not work) is always equal to the frequency of the network. There is no way to influence her.

In a double conversion UPS, the inverter always works – regardless of whether there is voltage in the network or not. If it is in the network, it is rectified, recharges the battery through the charger and enters the inverter controlled by the device controller. The inverter generates a clean, “synthetic”, sinusoid of a stable voltage – without interference and emissions.

Its frequency may differ from the frequency of the input voltage and is determined solely by the controller (more precisely, by the preliminary settings). When the mains voltage disappears or falls outside the normal range, the inverter switches to battery operation, maintaining the same high-quality signal at the output connectors.

In this case, switching occurs faster than in the first two types of sources. The double conversion UPS has a bypass (bypass, bypass line), which allows you to power the load directly from the mains. This is done so that the voltage supply to the load is not interrupted during overload or failure of the inverter (which always works).

If there are problems with the inverter, the controller switches the key, and the filtered mains voltage enters the load through the bypass.

In conclusion, we note that for the convenience of work, specialized software has been developed that allows, in particular, to track how the input mains voltage changed during operation.

UPS power (UPS)

In order to calculate the required UPS power, it is necessary to summarize the power of all consumers and add 20 … 25% to this amount. If the power of the UPS (UPS) is measured in VA, and the load power in W, then it is necessary to divide the load power by a power factor of 0.6 … 0.7 (in order to convert W to VA). The result of these calculations will be the required power of the UPS (UPS).

Tip: it is better to choose a UPS (UPS) with a capacity of 20 … 25% more power redundant equipment. Thus, over time, as the load power increases, there will be no need to replace the UPS.

UPS Battery life

The battery life of the UPS is on average 5 to 30 minutes. For longer battery life, it is necessary to install additional battery packs. Keep in mind that not all UPSs support the installation of additional battery packs.

The duration of battery life depends on the load connected to the UPS, the greater the load, the shorter the time. But we should not forget that the battery life, depending on the load, does not change linearly, that is, if the load is reduced by half, then the operating time can increase by 2-4 times, if by a factor of 3, then the time increases by 3-7 times and t .d.

UPS Maintenance
When choosing a UPS (UPS), you also need to pay attention to the service that the seller company provides. After all, whatever the perfect UPS (UPS), it requires periodic maintenance, which must be performed by certified specialists.

Additional UPS features
Before you buy, make sure that the UPS software (UPS) is compatible with your operating system (OS).

The software allows you to monitor the status of the UPS (UPS) and events in the network – the loss of the network and the transition to the battery, bypass operation and many other parameters.

Management with the help of software makes it possible to shut down applications, forcibly disconnect some loads to extend the work of more important applications. The software also notifies you of UPS malfunctions.

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