Uninterruptible power supply functions. UPS for a computer: what you should pay attention to when buying

Requirements for the quality of electricity are legally prescribed by state standards and fairly stringent regulations. Electricity supply organizations make a lot of efforts to comply with them, but they are not always implemented.

In our apartments, and in production, the following periodically arise:

complete power outages for an indefinite period of time;

aperiodic short-term (10÷100 ms) high-voltage (up to 6 kV) voltage pulses;

surges and drops in voltage with varying durations;

high-frequency noise overlays;

frequency drifts.

All these problems negatively affect the work of household and office electricity consumers. Microprocessor and computer devices are especially affected by the quality of power supply; they not only fail, but can also completely lose their functionality.

Purpose and types of sources uninterruptible power supply

To reduce the risk of malfunctions in the power supply network, backup devices are used, which are commonly called uninterruptible power supplies (UPS) or UPS (derived from the abbreviation of the English phrase “Uninterruptible Power Supply”).

They are manufactured with different designs to solve specific consumer problems. For example, powerful UPSs with gel batteries can maintain power supply to an entire cottage for several hours.

Their batteries receive a charge from the power line, wind generator, or other carriers of electricity through the inverter rectifier device. They also feed the electrical consumers of the cottage.

When the external source is turned off, the batteries are discharged to the load connected to their network. The larger the battery capacity and the lower their discharge current, the longer they work.

Medium power uninterruptible power supplies can back up indoor climate control systems and similar equipment.

At the same time, the simplest UPS models are only capable of completing the computer emergency shutdown program. At the same time, the duration of the entire process of their work will not exceed 9÷15 minutes.

Computer uninterruptible power supplies are:

built into the device body;

external.

The first designs are common in laptops, netbooks, tablets and the like mobile devices, powered by a built-in battery, which is equipped with a power and load switching circuit.

Laptop battery with a built-in controller is an uninterruptible power supply. His diagram in automatic mode protects operating equipment from electrical faults.

External UPS Designs, intended for the normal completion of programs desktop computer, are manufactured as a separate block.

They are connected via network adapter power to an electrical outlet. They power only those devices that are responsible for running programs:

system unit with a connected keyboard;

a monitor that displays ongoing processes.

Rest peripherals: scanners, printers, speakers and other equipment are not powered by UPS. Otherwise, in case of emergency termination of programs, they will take over part of the energy accumulated in the batteries.

Options for constructing UPS operating diagrams

Computer and industrial UPS are manufactured in three main options:

power backup;

interactive diagram;

double conversion of electricity.

With the first method backup scheme, denoted by the English terms “Standby” or “Off-Line”, the voltage is supplied from the network to the computer through a UPS, in which electromagnetic interference is eliminated by built-in filters. It is also installed here, the capacity of which is maintained by the charge current regulated by the controller.

When it disappears or goes beyond the established standards external power supply, then the controller directs the battery energy to power consumers. A simple inverter is connected to convert direct current into alternating current.

Benefits of UPS Standby

Off-Line uninterruptible power supplies have high efficiency when the voltage is applied to them, operate quietly, emit little heat and are relatively cheap.

Flaws

UPS Standby stand out:

long transition to battery power 4÷13 ms;

distorted shape of the output signal produced by the inverter in the form of a meander rather than a harmonic sinusoid;

lack of voltage and frequency adjustment.

Such devices are most common on personal computers.

Interactive circuit UPS

They are designated English term"Line-Interactive". They are carried out according to the previous, but more complicated scheme by including a voltage stabilizer using an autotransformer with step regulation.

This provides adjustments to the output voltage, but they are not able to control the signal frequency.

Filtering of interference in normal mode and switching to inverter power supply in case of emergency occurs according to UPS Standby algorithms.

The addition of a voltage stabilizer of various models with control techniques made it possible to create inverters with a signal shape not only of a square wave, but also of a sinusoid. However, a small number of control stages based on relay switching does not allow the implementation of full stabilization functions.

This is especially true for cheap models, which, when switching to battery power, not only increase the frequency above the nominal one, but also distort the shape of the sine wave. Interference is introduced by a built-in transformer, in the core of which hysteresis processes occur.

Expensive models use inverters based on semiconductor switches. UPS Line-Interactive have faster performance when switching to battery power than Off-Line UPS. It is ensured by the operation of synchronization algorithms between the incoming voltage and the output signals. But at the same time there is some underestimation of efficiency.

Line-Interactive UPS cannot be used to power asynchronous motors that are massively installed throughout household appliances, including heating systems. They are used to operate devices with power where the power is filtered and rectified at the same time: computers and consumer electronics.

Double conversion UPS

This UPS scheme is named after the English phrase “On-line” and works on equipment that requires high-quality power. It produces double conversion of electricity when sinusoidal harmonics alternating current are constantly converted by the rectifier into a constant value, passed through the inverter to create a repeated sine wave at the output.

Here the battery is permanently connected to the circuit, which eliminates the need for its switching. This method practically eliminates the period of preparation of the uninterruptible power supply for switching.

The operation of an On-line UPS based on the battery condition can be divided into three stages:

charge stage;

waiting state;

discharge for computer operation.

Charge period

The sine wave input and output circuits are interrupted by the internal UPS switch.

The battery connected to the rectifier receives charge energy until its capacity is restored to optimal values.

Readiness period

After the battery is charged, the automatic uninterruptible power supply closes the internal switch.

The battery maintains a state of readiness for operation in buffer mode.

Discharge period

The battery is automatically transferred to power the computer station.

Uninterruptible power supplies operating using the double conversion method have lower efficiency in line power mode than other models due to energy consumption for heat and noise. But in complex structures, techniques are used to increase efficiency.

UPS On-line is capable of correcting not only the voltage value, but also its oscillation frequency. This sets them apart from previous models and allows them to be used to power various complex devices with asynchronous motors. However, the cost of such devices is significantly higher than previous models.

UPS composition

Depending on the type of operating circuit, the uninterruptible power supply kit includes:

batteries for storing electricity;

Ensuring maintenance of battery performance;

inverter for generating a sine wave,

process control diagram;

software.

A local network can be used for remote access to the device, and the reliability of the circuit can be increased through its redundancy.

Some uninterruptible power supplies use the “Bypass” mode, when the load is powered by filtered mains voltage without operating the main circuit of the device.

The UPS part has a step voltage regulator “Booster”, controlled automatically.

Depending on the need to implement complex technical solutions, uninterruptible power supplies can be equipped with additional special functions.

An uninterruptible power supply is a component of the power system that is located between the load and the supply network. The main function of a UPS is to provide uninterruptible power. How does an uninterruptible power supply work? A simplified UPS circuit includes batteries and special UPS elements that compensate for disturbances in the main network, namely an inverter, a rectifier, a filter, and in some cases. Today, uninterruptible power supply systems are divided into three groups. Each group has its own operating principle of the UPS.

The key components of UPS are. It is the batteries that determine how long the UPS operates when the power is turned off. As a rule, UPSs use lead-acid batteries with the following parameters: voltage 12V and capacity 7Ah or 9Ah. The batteries are of the sealed and maintenance-free type. The simplest UPS uses 1 battery, but in powerful uninterruptible power supplies their number can be many times larger.

Backup UPS

The so-called backup UPSs are the simplest and most affordable. Operating principle of uninterruptible power supply of this type is extremely simple: the load is powered through the network if there is voltage there, otherwise the power is switched from the battery. The battery is charged while the UPS is operating. According to statistics, the efficiency of such UPSs during power failures is 55-60%.

In most cases, you can talk about how a UPS for a computer works by referring to the operating principle. Most home UPS systems for computers are made using this technology. The level of protection that they can provide is the lowest of all existing uninterruptible power supplies. The signal is filtered only partially. Often, this level of protection is quite sufficient for home appliances, since the quality of power in such networks is slightly higher than in industrial ones.

Backup UPSs work great in tandem with a computer, but they are absolutely not compatible for working in tandem with pumps, heating boilers and other similar equipment, since the operation UPS reserve type does not provide a sinusoidal voltage waveform. For computers this is not critical, since they use switched power supplies. This fact allows such devices to withstand a small power failure due to the presence of a certain amount of energy in their own capacitors. The offline switching time from the network to the battery ranges from 2 to 15 milliseconds. The UPS operating circuit includes an inverter, which converts the battery's direct current into alternating current. It should be noted that such UPSs are usually low-power.

Line-interactive UPS

The design and operation of interactive uninterruptible power supplies is almost identical to backup UPS. The exception is the ability to stabilize voltage, which is carried out using a switching device. The advantage of stabilization is that there is no need to switch the power supply in case of significant voltage deviations. Input voltage deviations can reach about 20% of the normal value. The output voltage of the uninterruptible power supply practically does not fluctuate. The protection efficiency of line-interactive UPSs is 85%.

Compared to standby UPSs, they provide more high level defense, but inferior. The operation of a linear-interactive uninterruptible power supply can be divided into two groups. Devices belonging to the first group produce an approximate sinusoid at the output, that is, a stepped one. The second group produces a “pure” sine wave without any distortion. The latter in some cases can become a replacement for an online UPS. The presence of a pure sinusoid at the output allows them to be used to protect electric motors and heating boilers.

Online UPS

The most reliable and high-tech UPSs are of the online type. They implement double conversion technology - the most advanced of all existing ones. The degree of protection provided by such devices tends to 100%, regardless of which operating modes of the UPS are active: from the network or from the battery.

How does a UPS with online topology work? In fact, the principle of operation is embedded in the name itself. The input current is converted to DC by the rectifier, after which the inverter converts it back to AC. The alternating current at the output has ideal parameters both in voltage form and in its value. The UPS contains a backup line - bypass, through which power is supplied in the event of a malfunction of any of the nodes of the uninterruptible power supply.

It is commonly said that the switching time to the battery is zero, but in reality the batteries are always connected to the circuit. That's why UPS data is called online. Such an uninterruptible power supply device allows you to protect the load from any types of disturbances that may occur in the backbone network.

Such UPSs are used to protect critical and very sensitive loads. All powerful UPSs are made using this technology. Despite the high power, additional solutions are used that allow increasing autonomy. Most often, the design allows the UPS to be used in conjunction with a generator or with external batteries.

However, double conversion also has its disadvantages. The UPS device is quite complex, which does not have the best effect on its cost. The presence of double conversion reduces the efficiency, but on modern UPSs it is quite high. Special energy saving technologies have been implemented to increase the efficiency to maximum values. In addition, the double conversion process is accompanied by heat generation and noise. It is worth recognizing that the proportion of all these disadvantages is incomparably small in comparison with all the advantages, and most importantly with the level of protection.

To maintain the functionality of devices during network failures, an uninterruptible power supply is used. Depending on the type of consumers served and electricity parameters, you need to choose different models. These devices are in demand, so purchasing a copy with the required characteristics is not difficult.

But before buying, you need to understand its features yourself, and not trust this issue to managers interested in sales.

In this material we will look at the design and operating features of the UPS, and also talk about the rules for its use.

For domestic needs, uninterruptible power supply devices are used, connected to a single-phase 220 V network, which can supply consumers requiring the same voltage for some time in the absence of electricity.

There are also UPSs that are connected to the input to a three-phase network, and the output is either 380 V or 220 V. However, they are expensive, they are used when it is necessary to obtain autonomous power from 10 kVA A, which is not required for domestic needs.

Household AC UPSs are divided into the following types according to their operating scheme:

• backup (offline);
• interactive (linear-interactive);
• double conversion (online).

They differ in the quality of the output voltage and price. The cheapest ones are standby ones, and the most expensive ones are double conversion ones.

To convert AC to DC in charger use a rectifier. And the reverse transformation occurs using an inverter.

In uninterruptible power supply systems, ordinary electromechanical relays are usually installed to switch the circuit from the network to the battery. If this part is of high quality, then its resource is enough for the entire operation of the UPS. But most often, when a block breaks down, the problem lies precisely in this structural element.

The interactive circuit differs from the backup circuit in the presence of a voltage stabilizer. It is designed as a typical autotransformer with directly connected windings

Voltage stabilization is also present in many household devices, so if the deviations are insignificant, then there is no point in purchasing a more expensive linear-interactive model.

The presence of a transformer often forces the manufacturer to use forced cooling, which is why such UPSs are equipped with coolers. They emit noise comparable in intensity to the operation of a computer system unit.

To measure the load of devices, you can either use an ammeter or calculate it using the readings of a meter installed in the apartment.

If there is a stabilizer, the voltage of the intra-house network will be brought to standard values. This will also affect devices that are not connected to the UPS.

When the voltage is reduced, the current flowing through the intra-house network increases. For example, let the total power of consumers connected to the UPS be 1.5 kW, and the supplied voltage be 190 V.

• I 1 = 1500 / 190 = 7.9 A – current strength in the circuit up to the UPS without a stabilizer;
• I 2 = 1500 / 220 = 6.8 A – current strength in the circuit up to the UPS with a stabilizer.

Thus, an intra-house network without a stabilizer will experience increased load, which may not have been taken into account when choosing the wiring cross-section.

Therefore, with a constant low voltage, it is better to install a stabilizer. In this case, the load on the UPS autotransformer will be less, which will extend its service life. In addition, taking into account voltage equalization, you can purchase cheaper uninterruptible power supplies.

Uninterruptible power supply to DC consumers

For some devices, it is necessary to provide uninterrupted power supply with DC 12, 24 or 48 V. A UPS of this type is also available for sale. Their markings contain the abbreviation “DC”. Units with a voltage supply of 60, 110 or 220 V also exist, but they are used in industry or energy.

The difference between DC uninterruptible power supplies in the internal structure from classical models is the absence of an inverter. The batteries are connected directly to the output through a contactor with a current-limiting measuring shunt to prevent unacceptably deep discharge of the batteries.

Sometimes there may be a stabilizing converter at the output if the devices powered by the UPS are sensitive to small voltage fluctuations.

These backup power supplies are used to protect the following DC-powered household equipment:

• and security;
• all kinds of sensors (leakage, smoke, fire, movement, etc.);
• lighting systems;
• telecommunication devices;
• communication systems;
• control system components.

Many DC UPSs have a connection option external batteries. In this case, the autonomous functioning of the devices they serve can be very long.

Conclusions and useful video on the topic

Briefly about the main characteristics of household UPS:

The variety of UPS types and their characteristics is a consequence of the different conditions of their use: the power and type of connected devices, parameters and typical problems of a particular electrical network. An uninterruptible power supply is usually not the most expensive element in the system, but the stability of its operation depends on it. Therefore, you need to determine the operating conditions and carefully select the model.

Still have questions about the topic of the article? Or can you supplement this material with interesting information about UPS? Please write your comments, ask questions, and share your experience in the block below.

The main purpose of an uninterruptible power supply (UPS) is to temporarily provide power to equipment during power outages. It is common practice to connect computers via a UPS everywhere. True, for many users this is a kind of “rule of good manners”, and the practical meaning of this ritual eludes them. “Well, a UPS protects your computer from power surges...” Let's try to figure it out: what, from what and how does the uninterruptible power supply protect?

By internal structure and operating logic, all UPSs are divided into three classes: passive, line-interactive and double conversion UPSs. Accordingly, they cope with incidents in the power grid to varying degrees and belong to different price categories.

Passive(stand-by, VFD, back-UPS, backup) sources are the simplest and cheapest. In them, the battery power circuit is usually turned off and starts only when there is a power failure. The switching time from mains operation to battery operation is tenths of a second, and the output signal when operating on battery power is noticeably different from the “correct” sine wave. As a rule, a simple noise filter and a high-speed fuse are installed at the input of such UPSs. The first partially smooths out impulse noise, and the second should operate when the voltage in the power network increases significantly. Passive UPSs are designed to power home and office PCs. A slight “dip” in the output voltage when switching to the battery computer units nutrition is not terrible.

Linear interactive(line-interactive, VI, Smart-UPS) UPSs differ in that the battery power circuit is constantly switched on. When the voltage at the input of the uninterruptible power supply disappears, its output sockets almost instantly switch to the internal converter - for the powered devices this transition is almost imperceptible. In addition, many line-interactive UPSs are capable of automatically maintaining an output voltage of 220 V. This is done in two ways.

As long as the mains voltage is between 175 and 275 V, the AVR (Automatic Voltage Regulation) mechanism is activated. When the input voltage deviates from 10 to 25% below the nominal value, the UPS increases the output voltage by 15%. When the input voltage deviates from 10 to 25% above the nominal value, the UPS reduces the voltage by 15%. If the mains voltage exceeds the limit values, the line-interactive UPS switches to battery power. In this mode, it continues to operate until either the mains voltage returns to normal or the battery is discharged. However, such UPSs should not be considered as voltage stabilizers. Their “stabilization” mode is forced and short-term!

IN Double conversion UPS(double conversion, VFI, Online-UPS) the output voltage is constantly supplied from the converter, the converter is constantly running on battery power, and the battery is continuously charged from the network. In fact, the input and output of the UPS are galvanically isolated from each other, and a stabilized voltage is supplied to the output. This is the most reliable, but at the same time uneconomical scheme. The UPS itself is expensive, large and heavy, the converter gets very hot and requires fan cooling, and energy losses during conversion amount to tens of percent.

Double conversion UPSs are used only to power servers and computers in critical applications. Such models rarely go on general sale - they are usually supplied to order. Most likely, to power your work computers you will purchase passive, maximum, line-interactive UPSs.

The power of uninterruptible power supplies is usually indicated in volt-amperes (VA, VA). To convert these values ​​into more familiar watts (W), you need to multiply the power in volt-amps by a factor of 0.6. For example, a UPS with a power rating of 600 VA will provide power to equipment with a maximum consumption of 360 W. If you give a large load, the current protection will work and the uninterruptible power supply will turn off. In practice, it is desirable to provide about 30% power reserve. Thus, the most common 600 or 650 VA UPSs are suitable for powering a computer with a real consumption of 200-250 W and a monitor, which takes about another 30-60 W.

If the arrangement of computers in the room allows, it is more profitable to use one powerful UPS instead of several small ones. Two office computers will require an uninterruptible power supply with a power of about 1000 VA. To power three computers standing next to each other, one source with a power of about 1400 VA is sufficient.

So what does a UPS protect against?

Filters in the power supply of the computer and monitor also do a good job of limiting impulse noise from the network. However, two filters are better than one! Surge protection is also important. If, for example, the neutral wire in the panel burns out, the voltage in the socket may be almost 380 V. In power supplies for computers and monitors, in this case, varistors and fuses usually burn out. Repairs are cheap, but take time. In theory, the UPS should respond to a voltage surge before the fuses in the equipment connected to it burn out.

However, data protection comes first. If the computer's power is turned off, all unsaved information is lost. The UPS allows you to either save open documents and shut down correctly, or put the computer into sleep mode. Manually saving documents is the easiest way. When switching to battery power, the UPS begins to beep loudly. Once you hear such a warning, check if everything is saved. Next, look at the situation: either simply turn off the computer, or put it into sleep mode.

To activate the automation, you need to connect the control port (USB or RS-232, depending on the model) of the uninterruptible power supply to the computer with a signal cable and install the necessary software on the computer. Unfortunately, many users are not even aware of this possibility! The operation of the UPS is controlled by a built-in microcontroller. Its microprogram (firmware) constantly monitors voltages and currents in external circuits when turned on and periodically tests the electronics and battery during operation. It also provides information about the current operating mode and the state of the UPS components to the control port. This data is transmitted via cable to a computer, where it is processed by a monitoring program.

To work with the UPS, it is advisable to use the program offered by its manufacturer. For example, for APC (www.apc.com) this is the Power-Chute program, for Ippon (www.ippon.ru) - WinPower2009 and Ippon Monitor, etc. The program can be installed from the disk included in the kit, but it is better to download the most its latest version from the manufacturer’s website.

You need to set parameters in the application settings automatic shutdown. As a rule, there are two options to choose from: either turn off the computer after a certain time after switching to backup power, or do it some time before the batteries are expected to be completely discharged.

How long can an uninterruptible power supply operate on battery power?

This depends on the battery capacity and power consumption. Most mass-produced models have one battery with a voltage of 12 V and a capacity of 7 Ah. Theoretically, a UPS with such a battery has an energy reserve of about 80 watt-hours. Simply put, it should power an 80 W load for about 1 hour, 160 W for half an hour, 300 W for about 15 minutes, etc. In reality, taking into account conversion losses, this time is approximately half that time.

In sources with a power of more than 800 VA, two of the same batteries or one, but with a larger capacity, are usually installed. Time tables or calculators battery life at different loads for different models are given on the manufacturers' websites. However, “offhand” we can assume that any model will be able to power a load of its rated power for about 5-15 minutes. If you need to provide power to your computer from batteries for a sufficiently long time, it is better to take a high-power UPS with capacious batteries. It will operate at only a third or a quarter of the rated power. But he will be able to supply such a load, low for himself, with energy for half an hour or longer.

Network equipment (switches, routers, NAS) also benefit from uninterruptible power supply. Otherwise, when the power goes out, the network will immediately “fall”, and documents opened from network folders will not be able to be saved. You can power the switch from the UPS of the workstation closest to it, although it is more correct to install a separate “uninterruptible power supply” of low power for this.

Battery life is limited. As it operates, its capacity steadily decreases and after 3-5 years of operation it drops to almost zero. Even before the indicator on the UPS signals the need to replace the battery, it becomes noticeable that the battery is no longer “holding a charge.” Each time the battery life gets shorter. In principle, a couple of minutes are enough to save documents and correctly turn off the computer. When the UPS starts to shut down even earlier, it’s definitely time to change the battery.

Replacing the battery is easy. In popular APC brand UPSs and some others, the battery is located under a removable hatch or cover. To get to the battery in UPS brands Ippon, SVEN and similar in design, you need to unscrew the four screws on the bottom and separate the halves of the case. In the instructions and on the official website, you are unlikely to find a description of self-disassembly and replacement: like printer manufacturers, UPS manufacturers receive a significant share of their income from the sale of “original” batteries with their installation in authorized service centers.

However, almost all computer stores sell sealed lead-acid batteries in the most popular sizes. The brand and manufacturer do not matter: these are completely standard products. First open your UPS and find out what kind of battery is installed in it. For most “office class” UPSs (500-700 VA), batteries marked 12V 7Ah with dimensions of 151x94x65 mm are suitable. When installing a new battery, try to fit the terminals tightly onto the battery contact tabs. If the terminals are loose, they can be carefully tightened with pliers.

After installing the battery, it is advisable to calibrate the UPS so that its firmware evaluates and remembers the parameters of the new battery. Fully charge the battery within 24 hours. After this, remove the plug from the socket so that the UPS switches to autonomous power supply. Allow the battery to completely discharge until the uninterruptible power supply switches itself off. It is better to use not a computer as a load (although in extreme cases this is acceptable), but several light bulbs with a total power of about 300 W. Then reconnect to the network and turn on the UPS - let the battery charge and the device continue to operate as normal. In addition to calibrating the device as a whole, this procedure also “trains” the battery. After a complete discharge-charge cycle, the battery begins to use its capacity to its maximum.

Why do many UPSs have telephone (RJ-11) and network (RJ-45) sockets?

By definition, uninterruptible systems do not need a telephone or a local network. Just as a “bonus”, pass-through impulse noise filters for the telephone line and network are installed in the same housing with the device. Connect one socket to the telephone socket on the wall, and plug in the telephone into the other. If high-voltage interference occurs in the telephone line, for example, during a thunderstorm, the filter will smooth out the voltage surge and protect the phone.

It is difficult to classify the electrical networks of Russian cities as modern. The equipment is outdated, repairs are not carried out, voltage drops have become the norm. All defects and malfunctions have an extremely negative impact on the work of consumers. Poor-quality power supplies have a particularly strong impact on computer and microprocessor devices, causing not only isolated failures, but also a complete loss of performance. Unfortunately, electrical equipment is often not protected from such surges, and an uninterruptible power supply will help solve the problem. According to the configuration of the phases of the outputs and inputs, UPSs are divided into two types: single-phase input - output and three-phase input - output.

Why do you need a UPS?

First of all, these devices prevent damage to equipment and prevent operational failures electronic systems. They make it possible to shut down work correctly in the event of an unexpected power outage.

With the help of a UPS, interruptions and electrical interference that periodically occur in home and work networks are successfully overcome. Among them, the most common are the following:

• Voltage dips. In this state, the voltage suddenly drops by a significant amount. To restore it, various time intervals are required, in some cases tens of seconds. The cause of failures is most often associated with the limited capacity of the substation, especially in winter, as well as with the startup and further operation of powerful equipment. Physically, low voltage manifests itself in the form of flickering lights.
• Voltage impulse. In this case, the voltage changes sharply, with an amplitude of up to 2000 volts, and then returns to the normal level within a very short time. a short time. This requires no more than 10 milliseconds. The main reason is considered to be the operation of industrial equipment, air conditioners, elevators, lightning strikes, etc.
• No voltage for a short time. This gap is no more than 20 milliseconds and is practically unnoticeable. However, electronic equipment is negatively affected
• No tension for a long time. This period can range from 20 milliseconds to several hours. Causes include overloads, adverse weather conditions and physical damage at substations that cause power lines to go down.
• Changes in frequency over a short period of time when high-power equipment is connected to the network. RF noise also has a negative impact when connecting radio transmitters, loads, generators and industrial equipment.

Electronics companies have conducted studies that show that every Personal Computer within a month, at least 120 times are exposed to various negative influences, one way or another related to voltage problems in electrical networks.

Basic functions of the UPS

In accordance with known problems that regularly arise in electrical networks, uninterruptible power supplies perform a number of important functions aimed at eliminating them and preventing negative consequences.

The purpose of an uninterruptible power supply is to do the following:

• They filter the supply voltage and reduce the noise level.
• Absorbs short-term voltage surges, including minor ones.
• Protects against short circuits and overloads.
• In the absence of voltage in the network, they provide the load with backup power supply for a set period of time.

The most advanced models of uninterruptible power supply systems can perform additional useful actions, thanks to specialized software, designed to control these devices:

• The load is turned on and off according to commands from the internal timer exactly at the specified time.
• In the event of a prolonged power outage, the equipment is automatically maintained, as well as restarted after the normal power supply is restored.
• Emergency situations are monitored and various warning signals are issued.
• The device display shows the AC voltage and frequency in a given network, as well as the output supply voltage and power consumed by the load.
• Monitoring and recording data regarding the state of the UPS. This includes battery temperature, charge level, and other performance characteristics.

General diagram of operation of uninterruptible power supply devices

Most UPSs are equipped with the following components according to their operating patterns:

• An inverter that generates a sine wave.
• Rechargeable batteries that store electricity.
• Electronic circuit to manage all processes.
• Software.
• Battery charging device.

If necessary, the device can be organized remote access using a local network. The reliability and performance of the circuit is increased by its redundancy.

Uninterruptible power supplies can be in the following operating modes:

• Charging period. The sine wave circuit at the input and output is interrupted by the internal switch of the device. The battery connected to the rectifier is charged until its optimal capacity is restored.
• Ready period. Once the battery is charged, the device's internal switch automatically closes. The battery goes into buffer mode and maintains a state of readiness for further operation.
• Discharge period. The battery is automatically transferred to power the load, which leads to its gradual discharge.

Specifications

All uninterruptible power supply devices have a certain set technical characteristics. They differ in individual parameters, depending on the design and modification of a particular device.

Each of them has its own input voltage ranges when the UPS operates from the mains and does not use the built-in batteries. It should be remembered that longer ranges reduce battery life, thereby increasing their service life. In addition, they continue to supply power to the load from the mains, whereas at a lower range the UPS switches to the battery, quickly discharging it and de-energizing the load.

For all UPS, the output voltage changes when the input voltage changes. That is, it must be maintained at such a level that the connected equipment can operate normally. Low output voltage often leads to malfunctions and data loss. Exceeding gives the same results, and is complemented by failure of the load used.

Of great importance is the quality of switching and transient processes to and from the battery, which should not attract attention and be carried out correctly in a short period of time. The UPS frequency is correctly synchronized with the external mains frequency. In the event of an overload, a special signal is given using light and sound indication. The device itself is switched off when operating from the battery, and the user must promptly reduce the load.

Many devices can be turned on in the so-called cold start mode, when there is no voltage in the main power supply. This function is useful during a long power outage, when it is necessary to urgently perform some action on electronic equipment.

Single-phase input - output (1ph / 1ph or 1:1)

Single-phase uninterruptible power supplies were designed for single-phase power supply. They reliably protect electrical equipment that requires increased requirements for the quality of power supply, from any problems in the network (for example, absence or distortion of voltage, suppression of high-frequency interference).

Such equipment maintains the quality of the output voltage if there is a problem with the input voltage by using energy batteries(deviations in value, disappearance, distortion of shape). Single-phase UPSs are used in many areas of information technology and communications.

Three-phase input - output (3ph / 3ph or 3:3)

Three-phase types of uninterruptible power supplies are usually used for continuous 24/7 operation. The device is suitable for powering three-phase equipment, which is designed for 3x380 V and for single-phase energy consumers operating at 220 V. Three-phase UPS maintain the required quality of the output voltage. They are used in banks, computer centers, medical centers, transport, etc.

Types of uninterruptible power supplies

Based on its type, the uninterruptible power supply is divided into three categories.

Interactive UPS (line-interactive)

This is the most ideal option for the home, namely where the voltage is unstable and often disappears. Compared to other types, there are two important aspects. First, they operate much faster, in 2-5 milliseconds. Second, before switching, they try to equalize the voltage, which works quite effectively with small surges. As a result, battery life improves and a lot of money can be saved. This is an ideal option for home use.

These devices are distinguished by a more complex circuit, which includes a voltage stabilizer with an autotransformer that has a step control function. These devices only adjust the output voltage, but cannot control the frequency of the signals. Complete stabilization is impossible due to the small number of adjustment steps.

More expensive types of models are equipped with inverters with semiconductor switches. When switched to battery power, they are faster than other devices.

Offline uninterruptible power supply UPS (off-line)

The most inexpensive type. The principle of operation is that in the event of a power failure or surge, switch the equipment to battery power. This type has significant disadvantages. The first is the response time, it is about 10 milliseconds. Secondly, if the voltage in your home is constantly fluctuating, such a UPS will often switch to battery power, this will significantly reduce its resource and you will have to change it after a few months.

Online UPS (on-line)

The most expensive and efficient uninterruptible power supply. It regulates voltage in real time, switching to the battery only in the most difficult situations. Often used for servers that require high-quality power. The battery is permanently connected to the circuit and does not require any additional switching.

How to choose the right UPS

Before choosing a device, you need to decide which power supply problems will be most pressing.

For residents of new areas located in large cities, the simplest offline devices will be sufficient. In these places, new networks are usually laid that provide stable voltage. Therefore, in addition to the UPS, it is recommended to purchase a surge protector just in case. It cannot be connected to the output of an uninterruptible power supply to avoid distortion of the current characteristics. When choosing uninterruptible power supplies for offices and large local networks You can choose any of the options discussed above, in accordance with operating conditions.

When choosing an uninterruptible power supply (UPS), you should pay attention to the following parameters and technical characteristics:

• Output power value
• The time required to switch to battery power and back.
• Battery life, depending on battery capacity and power of equipment connected to the UPS.
• The width of the input voltage range at which power can be stabilized without switching to batteries.
• The battery life is on average from 5 to 10 years.