How to use an uninterruptible power supply. How uninterruptible power supplies (UPS) are designed and operate. Type of power failure

As civilization develops, it begins to consume more and more energy, in particular electrical energy - machines, factories, electric pumps, street lights, lamps in apartments... The advent of radios, televisions, telephones, computers gave humanity the opportunity to speed up the exchange of information, however, it tied them even more it to sources of electricity, since now, in many cases, a loss of electricity is tantamount to the loss of a channel for delivering information flow. This situation is most critical for a number of the most modern industries, in particular, where the main production tool is computer networks.

It has long been calculated that after a couple of months of operation, the cost of information stored on a computer exceeds the cost of the PC itself. Information has long become a type of commodity: it is created, evaluated, sold, bought, accumulated, transformed... and sometimes lost for a variety of reasons. Of course, up to half of the problems associated with information loss arise from software or hardware failures in computers. In all other cases, as a rule, problems are associated with poor-quality power supply to the computer.

Ensuring high-quality power supply to PC components is the key to stable operation of any computer system. The fate of entire months of work sometimes depends on the shape and quality characteristics of the mains power supply, and on the successful choice of power components. Based on these considerations, the research methodology outlined below was developed, which is intended to later become the basis for testing the quality characteristics of uninterruptible power supplies.

1. GOST provisions
2. UPS classification (description, diagram)
   • Offline
   • Linear interactive
   • Online
   • Main types by power
3. Physics
   • a. Types of power, calculation formulas:
     • Instant
     • Active
     • Reactive
     • Full
4. Testing:
   • Purpose of testing
   • General plan
   • Parameters to check
5. Equipment used in testing
6. Bibliography

GOST provisions

Everything related to electrical networks in Russia is regulated by the provisions of GOST 13109-97 (adopted by the Interstate Council for Standardization, Metrology and Certification to replace GOST 13109-87). The standards of this document are fully consistent with international standards IEC 861, IEC 1000-3-2, IEC 1000-3-3, IEC 1000-4-1 and publications IEC 1000-2-1, IEC 1000-2-2 regarding electromagnetic compatibility levels in power supply systems and methods for measuring electromagnetic interference.

Standard indicators for electrical networks in Russia, established by GOST, are the following characteristics:

• supply voltage 220 V±10%
• frequency 50±1 Hz
• coefficient nonlinear distortion voltage forms less than 8% for a long time and 12% short-term

Stipulated in the document and typical problems electricity supply Most often we encounter the following:

• Complete loss of voltage in the network (no voltage in the network for more than 40 seconds due to disturbances in the power supply lines)
• Sags (short-term decrease in network voltage to less than 80% of the nominal value for more than 1 period (1/50 of a second) are a consequence of the inclusion of powerful loads, externally manifested as flickering of lighting lamps) and surges (short-term increases in network voltage by more than 110% of the nominal value for more than 1 period (1/50 of a second); appear when a large load is turned off, externally appear as flickering of lighting lamps) voltages of different durations (typical for large cities)
• High-frequency noise radio frequency interference of electromagnetic or other origin, the result of high-power high-frequency devices, communications devices
• Frequency deviation outside acceptable values
• High-voltage surges short-term voltage pulses up to 6000V and lasting up to 10 ms; appear during thunderstorms, as a result of static electricity, due to sparking switches, have no external manifestations
• Frequency run-out change in frequency by 3 or more Hz from the nominal (50 Hz), appears when the power source is unstable, but may not appear externally.

All these factors can lead to failure of fairly “thin” electronics and, as often happens, to loss of data. However, people have long learned to protect themselves: line voltage filters that “dampen” surges, diesel generators that supply electricity to systems in the event of a power outage on a “global scale”, and finally, sources uninterruptible power supply the main tool for protecting personal PCs, servers, mini-PBXs, etc. It is the last category of devices that will be discussed.
UPS classification

UPS can be “divided” according to various criteria, in particular, by power (or scope of application) and by type of operation (architecture/device). Both of these methods are closely related to each other. Based on power, UPSs are divided into

1. Uninterruptible power supplies low power(with total power 300, 450, 700, 1000, 1500 VA, up to 3000 VA including on-line)
2. Low and medium power(with total power 3–5 kVA)
3. Medium power(with total power 5–10 kVA)
4. High power(with total power 10–1000 kVA)

Based on the principle of operation of the devices, two types of classification of uninterruptible power supplies are currently used in the literature. According to the first type, UPSs are divided into two categories: on-line And off-line, which in turn are divided into reserve And linear-interactive.

According to the second type, UPSs are divided into three categories: reserve (off-line or standby), linear-interactive (line-interactive) and Double conversion UPS (on-line).

We will use the second type of classification.

Let's first consider the difference between UPS types. Reserve type sources are made according to a circuit with a switching device, which in normal operation ensures that the load is connected directly to the external power supply network, and in emergency mode it switches it to power from batteries. The advantage of a UPS of this type can be considered its simplicity; the disadvantage is the non-zero switching time to battery power (about 4 ms).

Line-interactive UPS made according to a circuit with a switching device, supplemented by an input voltage stabilizer based on an autotransformer with switchable windings. The main advantage of such devices is protecting the load from overvoltage or undervoltage without going into emergency mode. The disadvantage of such devices is also the non-zero (about 4 ms) switching time to batteries.

Double conversion UPS voltage differs in that in it the alternating voltage arriving at the input is first converted by a rectifier into constant, and then, using an inverter, again into alternating. The battery is constantly connected to the output of the rectifier and the input of the inverter and powers it in emergency mode. Thus, a fairly high stability of the output voltage is achieved regardless of input voltage fluctuations. In addition, interference and disturbances that abound in the power supply network are effectively suppressed.

In practice, UPSs of this class, when connected to an AC network, behave like a linear load. The advantage of this design can be considered zero switching time to battery power, the disadvantage is a decrease in efficiency due to losses during double voltage conversion.

Physics

In all reference books on electrical engineering, four types of power are distinguished: instant, active, reactive And full. Instantaneous power is calculated as the product of the instantaneous voltage value and the instantaneous current value for an arbitrarily selected point in time, that is

Since in a circuit with resistance r u=ir, then

The average power P of the circuit under consideration over the period is equal to the constant component of the instantaneous power

The average AC power over a period is called active . The unit of active power volt-ampere is called watt (W).

Accordingly, resistance r is called active. Since U=Ir, then

Typically, active power is understood as the power consumption of a device.

Reactive power a value characterizing the loads created in electrical devices by energy fluctuations electromagnetic field. For a sinusoidal current, it is equal to the product of the effective current and voltage and the sine of the phase shift angle between them.

Full power total power consumed by the load (both active and reactive components are taken into account). Calculated as the product of the rms values ​​of the input current and voltage. Unit of measurement is VA (volt-ampere). For sinusoidal current it is equal to

Almost every electrical device has a label indicating either the total power of the device or the active power.
Testing

Main purpose of testing demonstrate the behavior of the tested UPS in real conditions, give an idea of ​​additional characteristics that are not reflected in the general documentation for the devices, determine in practice the influence of various factors on the operation of the UPS and, possibly, help determine the choice of a particular uninterruptible power supply.

Despite the fact that there are currently a great many recommendations for choosing a UPS, during testing we expect, firstly, to consider a number additional parameters, which are worth asking before purchasing equipment; secondly, if necessary, adjust the set of selected testing methods and parameters and develop a basis for future analysis of the entire power supply path of the systems.

The general testing plan is as follows:

• Specifying the device class
• Indication of characteristics declared by the manufacturer
• Description of delivery contents (presence of manual, additional cords, software)
• Short description appearance UPS (functions located on the control panel and list of connectors)
• Battery type (indicating battery capacity, serviceable/non-serviceable, name, possible interchangeability, possibility of connecting additional battery packs)
• “Energy” component of tests

During testing, it is planned to check the following parameters:

• The range of input voltage at which the UPS operates from the mains without switching to batteries. Larger input voltage range reduces the number of UPS transfers to battery and increases battery life
• Time to switch to battery power. The shorter the switching time, the lower the risk of failure of the load (device connected via the UPS). The duration and nature of the switching process largely determine the possibility of normal continued operation of the equipment. For a computer load, the permissible power interruption time is 20-40 ms.
• Oscillogram of switching to battery
• Switching time from battery to external power
• Oscillogram of switching from battery to external power
• Offline operating time. This parameter is determined solely by the capacity of the batteries installed in the UPS, which, in turn, increases as the maximum output power of the UPS increases. To provide autonomous power supply for two modern computers SOHO typical configuration for 15-20 min, maximum output power The UPS should be about 600-700 VA.
• Output voltage parameters when operating on batteries
• Pulse shape at the beginning of battery discharge
• Pulse shape at the end of battery discharge
• The UPS output voltage range when the input voltage changes. The narrower this range, the less the impact of changes in input voltage on the powered load.
• Output voltage stabilization
• Output voltage filtering (if available)
• Behavior of the UPS during output overload
• Behavior of the UPS during load loss
• Calculation of UPS efficiency. Defined as the ratio of the device's output power to the power input from the power source
• Nonlinear distortion coefficient, characterizing the degree to which the voltage or current waveform differs from the sinusoidal one
  • 0% sine wave
  • 3% distortion is not noticeable to the eye
  • 5% distortion visible to the eye
  • up to 21% trapezoidal or step waveform
  • 43% signal is square wave

Equipment

When testing, we will not use real workstations and servers, but equivalent loads that have a stable consumption pattern and a power utilization factor close to 1. The following set is currently being considered as the main equipment that will be used during testing:

Bibliography

1. GOST 721-77 Power supply systems, networks, sources, converters and receivers of electrical energy. Rated voltages over 1000 V
2. GOST 19431-84 Energy and electrification. Terms and Definitions
3. GOST 21128-83 Power supply systems, networks, sources, converters and receivers of electrical energy. Rated voltages up to 1000 V
4. GOST 30372-95 Compatibility technical means electromagnetic Terms and Definitions
5. Theoretical Electrical Engineering, ed. 9th, corrected, M.-L., publishing house "Energia", 1965
6. Company promotional materials
7. Internet resource

All types of uninterruptible power supplies are designed to perform a set of the following basic functions

• Protection against small and short-term failures in the main power supply network.
• Filtering of emerging impulse disturbances and noise reduction.
• Backup power supply to the load during the set automation period.
• Short circuit and overload protection.

More complex models have a set of additional functions:

• Automatic deactivation of protected equipment during longer critical power outages, as well as restart when the required parameters are restored.
• Monitoring the main parameters of the source’s functioning, tracking its performance level.
• Displays basic information about the operating UPS, as well as the parameters of the input voltage of the supply network.
• Automatic alarm when abnormal calls occur.
• Availability of an installed timer for configurable shutdown or switching on of the consumer at a set time.

Scope of application depending on UPS type

Backup uninterruptible power supply- the most common in this market segment. It is widely used in combination with home or office computers or low-power LAN workstations. It is also effective in terms of protecting household appliances, which do not require special quality of power supply, allow power outages for a certain time and the occurrence of deviations from the input voltage parameters on average +-5%.

Interactive uninterruptible power supply can also act as a backup. However, its main tasks are broader: it also performs stepwise voltage stabilization, which allows it to be used in combination with electrical devices with high inrush currents. This is any device or other equipment that uses an electric motor, the starting of which requires increased power for a short time. In particular, the operation of a refrigerator under conditions of deviation from normal voltage parameters can lead to its overload and failure. However, the coefficient useful action of these protective devices is slightly lower than the same parameter for backup devices.

Online or double conversion uninterruptible power supply provides the most effective protection for file servers and more complex workstations. It is used in combination with equipment from financial institutions, medical clinics and research centers. That is, almost everywhere where absolutely high-quality energy supply is needed with the absence of even short-term voltage dips. But in everyday life, such devices are, firstly, ineffective (high cost at low loads), and they are also characterized by increased noise and impressive heat generation.

Application by current type

Online or double conversion uninterruptible power supply

Such uninterruptible power supplies are necessary to ensure the protection of electrical devices that are connected to a 24 V, 48 V and 60 V network.

AC UPS

Uninterruptible power supplies of this type are used in combination with critical consumers that require a voltage of 220 or 380V.

Application by power

UPSs are divided into three groups based on power:

• - low-power;
• - medium power devices;
• - modular high power systems.

Low-power UPSs are widely used for domestic purposes, as well as to protect individual consumers from possible critical situations in offices or small industries.

Medium power devices are responsible for high-quality and uninterrupted power supply of local networks, data centers and various telecommunications equipment, as well as remote communication facilities.

A high-power uninterruptible power supply has several advantages in use. It is capable of providing protection for both a separate residential cottage and a large production process. In addition, such a UPS is a kind of modular system that allows you to synchronize several sources into one 19" rack to obtain higher power values ​​when solving specific technological problems.

UPS stands for "uninterruptible power supply". Abbreviation in English - UPS (Uninterruptible Power Supply) , therefore the names UPS, YUPS, and oopsnik are also common.

The main function of an uninterruptible power supply is to ensure the supply of electricity to the equipment connected to it during outages in the main network. But, depending on the type of equipment, the parameters of such autonomous power supply may be required to be radically different. Accordingly, the UPS market offers different types devices that differ in a lot of parameters:

• principle of operation: offline, linear-interactive, online;
• type of automatic voltage regulation;
• quality of filtering network interference;
• capacity (number of ampere-hours, or in other words - for how long battery life that's enough);
• time to switch to batteries during a power outage;
• possibility of connecting additional external batteries;
• various additional functions (filtering sockets, sockets for telephone and network cables, LCD display, synchronization with a PC), etc.

How to choose a UPS with such a variety of models ? How to understand how they differ? In this article we will look at the main types of uninterruptible power supplies, their differences, and what additional functions manufacturers equip UPS with. In the next one - how to choose a UPS depending on the features of your equipment, how to calculate its required power, etc.

Three main types of UPS

Off-line (Back-UPS, backup, Standby) uninterruptible power supply

Example of a backup UPS: model .

The operating principle of this type of uninterruptible power supply is very simple:

As long as there is electricity in the network within the set values, the UPS supplies the connected devices with voltage directly from the network, while simultaneously recharging the battery. The power passing through the UPS is not regulated; pulses and noise are filtered at the simplest level, using passive filters. The signal shape corresponds to the network signal, i.e., a sinusoid.

As soon as the mains power is lost, the UPS switches to battery power. Inverter converting D.C. from the battery to AC output, this type of UPS has one of the simplest installed, so the waveform does not follow the correct sine wave. The maximum that manufacturers do is to bring it somewhat closer to a sinusoid, making it stepwise.

The UPS also switches to off-line autonomous power supply if the voltage level in the network falls below or rises above the threshold values, they can be different depending on the brand of uninterruptible power supply.

The switching time to batteries in various models ranges from 5 to 20 ms. This is relatively long, and for some equipment models such a long delay may adversely affect operation . The long-term operation of the relay is due to the fact that the device needs the phases of the mains and battery voltages to coincide when the autonomous power is turned on, and since they are not synchronized, this takes some time.

Scheme of operation of a backup uninterruptible power supply.

Pros of Standby UPS:

• inexpensive price,
• high efficiency,
• silent operation.

Flaws:

• long switchover to battery operation (from 5 to 20 ms);
• the output signal shape is not a sinusoid;
• filtering interference, noise and impulsesquite rough on the line;
• there is no voltage and frequency adjustment when operating from the network.

Line-interactive UPS

Example of a line-interactive UPS: model

Buyers choose this type of uninterruptible power supply most often, as it optimally combines functionality and price.

IN schematic diagram operation of line-interactive UPS includes AVR - module for automatic regulation of incoming network voltage. That is, unlike a backup UPS, it not only passes power through itself, but also stabilizes it, although not smoothly, but in steps.

When operating from the mains at normal voltage levels, the line-interactive uninterruptible power supply passes the incoming signal through passive interference and noise filters, while the battery is charged.

When the voltage in the network increases or decreases, the line-interactive UPS makes its stepwise adjustment. When the voltage reaches a certain threshold, the AVR lowers or lowers it by a fixed amount (or percentage). Several such threshold-steps can be specified in the AVR operating scheme; also, for working with a lower and higher level, a different number of adjustment steps can be assigned (for example, 2 for an increase, and 1 for a decrease).

If the mains voltage drops or rises to values ​​that lie outside the available input range of the uninterruptible power supply, the device switches to battery operation, just as in the case of a complete power outage. These minimums and maximums may vary depending on the load on the UPS. For example, if the UPS is 70% loaded and the voltmeter shows 160V in the network, the uninterruptible power supply switches to the batteries. And at 30% load and a voltage of 150V, it still makes adjustments using an AVR transformer.

Some linear-interactive models are no different in the shape of the output signal from backup-type uninterruptible power supplies: they have a stepped sine wave. Some manufacturers, especially with the growing demand for UPS for boilers, equip their uninterruptible power supply systems with inverters that produce the correct sine wave.

The switchover time to battery operation in a pure sine wave line-interactive UPS is faster than that of its standby counterparts. The reason is that in UPSs of this type, the voltage waveforms coincide (both from the network and from the battery, this is a sinusoid), which speeds up phase synchronization and, accordingly, the start of autonomous power supply.

Pros of line-interactive UPS:

• reasonable price,
• silent operation,
• automatic regulation of incoming voltage,
• in some models - pure sine wave at the output,
• switching time is less than in backup ones (on average 4-8 ms, in some models 2-4 ms).

Flaws:

• no frequency adjustment,
• insufficiently complete filtering of interference, noise and network impulses,
• voltage regulation is not smooth, but stepwise,
• The efficiency is lower than in an off-line uninterruptible power supply.

Double conversion UPS (on-line)

Double conversion UPS example: model .

This is the most expensive, but also the most best view UPS. It is optimally suited for expensive, capricious equipment, for which not only constant voltage is important, but also frequency, as well as effective noise filtering, a signal in the form of a pure sine wave, and the absence of delays when switching to battery operation.

In fact, such an uninterruptible power supply operates constantly, stabilizing, filtering the incoming signal, equalizing the frequency and shape of the output signal.

In mains mode, the incoming AC voltage is stabilized and converted to DC by the rectifier and distributed between the battery (for recharging if necessary) and the inverter. The inverter converts direct current into alternating current, producing an output signal in the form of a pure sine wave, the correct frequency, the correct voltage. Interference and noise are completely absent - they simply do not remain after double conversion.

This constant “inclusion” of the uninterruptible power supply into the network provides one of its significant advantages: Instant switching to battery operation. Actually, it’s hard to even call it “switching”, since power passes through the rectifier, battery (during charging) and inverter constantly. When the network voltage drops below threshold values ​​or there is a complete power outage, the inverter simply begins to take part of the energy from the battery, and not from the rectifier. It happens instantly.

Double conversion UPSs usually have another operating mode: bypass. This is a backup line that goes directly from the input to the output of the UPS, bypassing the rectifier, battery and inverter. It allows in critical moments for the UPS: overload (for example, with starting currents), failure of the inverter and others - to supply electricity directly to the connected devices, avoiding failure of the device elements.

Constant operation of the UPS has a certain disadvantage: increased heat generation, which requires effective cooling. Therefore, UPS online are most often equipped with fans, which makes their operation in residential areas not as comfortable as other types of silent uninterruptible power supplies.

Pros of online UPS:

• constant voltage stabilization,
• constant frequency stabilization,
• pure sine wave at the output,
• effective filtering of noise, impulses and interference,
• Instant switching to batteries.

Flaws:

• high price,
• increased noise level,
• the lowest efficiency among all types of UPS.

When choosing an uninterruptible power supply, you need to take into account that there are exceptions. Some line-interactive UPSs may cost more than online models from another manufacturer, the switching time to battery operation in a backup UPS may be no more, or even less, than in some line-interactive UPS, etc. Therefore, In any case, you need to read the specifications specific model.

Additional UPS functionality

In addition to determining the type of uninterruptible power supply you need, when choosing a UPS you should also pay attention to what functionality is included in it. UPS can have various additional functions and design features:

Synchronization with PC. This feature is not present in the cheapest models, but it is very convenient. Using a special software The UPS transmits data in real mode to the computer about the state of the power line and battery charge level. In addition to the purely informational component, there are also features such as, for example, autonomous shutdown of the computer while saving data in all applications during a power outage.

Cold start. An uninterruptible power supply equipped with this function can be turned on when there is no power in the network. For example, the lights went out, you saved the documents, turned off the computer and UPS, but after some time there was an urgent need to copy the document to a flash drive. A UPS with cold start support can be turned on, even if there is still no power, and get the job done.

Previously, connectors for connecting devices in a UPS looked basically like this:

This IEC 320 standard connector is perfect for connecting various computer equipment. However, equipment with a regular power cord is the same WiFi router, you can’t connect it to it. For these purposes, you can use a surge protector with a similar connector, which is connected to the UPS, and then connect various equipment to it. But this is not always convenient.

Therefore, now many models have simply begun to be supplemented with Schuko-type sockets (in our country they are often called Euro sockets) so that the equipment can be turned on directly:

Sockets for filtering interference. A UPS may be equipped with an outlet or several for sensitive equipment that does not provide power support during a power outage but protects the connected equipment from utility power interference.

Sockets for telephone line, twisted pair. High-voltage pulses can be transmitted not only directly via electrical power cable, but also in the event of various accidents and breakdowns - both via telephone cable and twisted pair cable. To protect telephone, network and computer equipment, some manufacturers provide special connectors (input/output) where you can connect a telephone or Internet line.

To be continued in the next article.

website

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?

According to the internal structure and logic of operation, 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 small “dip” in the output voltage at the moment of switching to the battery is not dangerous for computer power supplies.

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 from the battery, 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 expected full discharge batteries

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. Tables or calculators for determining battery life at different loads for different models are provided 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. You are unlikely to find a description in the instructions or on the official website self-disassembly and replacements: 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?

Neither phone nor the local network“uninterruptible systems” are not needed by definition. 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.

Before you buy a new UPS, you should familiarize yourself with some of the “internal” aspects of its operation. To ensure that your uninterruptible power supply serves you as long as possible and that your investment is as effective as possible, try to follow the tips below.

What batteries are used in the UPS

All UPS manufactured by APC (and other well-known major UPS manufacturers) use lead acid. rechargeable batteries, very similar to the most common car batteries. The difference is that, if we are to make such a comparison, the batteries used by APC are made using the same technology as the most expensive car batteries available today: the electrolyte contained inside is in a gel-like state and does not spill if the case is damaged; The battery is sealed, as a result of which it does not require maintenance, does not emit harmful and explosive gases (hydrogen) during operation, it can be “turned over” in any way without fear of spilling the electrolyte.

How long do UPS batteries last?

Although different UPS systems appear to use the same battery technology, the lifespan of UPS batteries from different manufacturers varies widely. This is quite important for users, since replacing batteries is expensive (up to 30% of the original cost of the UPS). Battery failure reduces system efficiency, causing downtime and unnecessary headaches. Temperature has a significant impact on battery reliability. The fact is that the natural processes that cause battery aging largely depend on temperature. Detailed test data provided by battery manufacturers shows that battery life decreases by 10% for every 10°C increase in temperature. This means that the UPS must be designed to minimize battery heating. All UPSs with an online topology and hybrid online sources heat up more than standby or line-interactive ones (which is why the former require a fan). This is the most important reason why UPSs of standby and line-interactive types require battery replacement less often than UPSs with an online topology.

Should you pay attention to the design of the charger when choosing a UPS?

The charger is an important component of the UPS. The conditions under which batteries are recharged have a significant impact on their longevity. The UPS battery life is maximized if it is continuously charged from a constant or floating voltage charger. In fact, the service life of a rechargeable battery significantly exceeds the period of simple storage. This happens because some natural aging processes are halted by constant recharging. Therefore, it is necessary to charge the battery even if the UPS is turned off. In many cases, the UPS is turned off regularly (if the load being protected is turned off, there is no need to keep the UPS on, since it may trip and cause unwanted wear and tear on the battery). Many commercially available UPSs do not provide the important feature of continuous charging.

Does voltage affect reliability?

Batteries are made up of individual cells of approximately 2V each. To create a higher voltage battery, individual cells are connected in series. A 12-volt battery has six cells, a 24-volt battery has 12 cells, etc. When the battery is on trickle charge, as in UPS systems, the individual cells are recharged simultaneously. Due to the inevitable dispersion of parameters, some elements take a larger share of the charging voltage than others. This causes premature aging of such elements. The reliability of a group of series-connected elements is determined by the reliability of the least reliable element. Therefore, when one of the cells fails, the battery as a whole fails. It has been proven that the rate of aging processes is directly related to the number of elements in the battery; therefore, the rate of aging increases with increasing battery voltage. The best types of UPS use fewer higher-power elements instead of more lower-power elements, thereby achieving increased reliability. Some manufacturers use high-voltage batteries, which, for a given power level, can reduce the number of wiring connections and semiconductors, thereby reducing the cost of the UPS. The battery voltage of most typical UPSs with a power of about 1 kVA is 24...96 V. At this power level, the batteries of APC UPSs, in particular the Smart-UPS family, do not exceed 24 V. Low voltage batteries in UPSs manufactured by APC, have a longer service life compared to competing devices. The average service life of APC batteries is 3-5 years (depending on temperature conditions and frequency of discharge/charge cycles), while some manufacturers indicate a service life of only 1 year. Over the 10-year lifespan of a UPS, some system users spend twice as much on batteries as they do on the unit itself! Although developing a UPS using high-voltage batteries is easier and cheaper for the manufacturer, there is a hidden cost to the user in the form of a shorter UPS life.

Why "pulsating" current reduces battery life

IN ideal To increase the operating time, the UPS battery must be constantly kept on “floating” or constant recharging. In this situation, a fully charged battery draws a small amount of current from the charger, called float or self-charging current. Despite battery manufacturers' recommendations, some UPS systems additionally expose batteries to ripple current. Ripple currents occur because the inverter that produces AC current for the load consumes DC current at its input. The rectifier, located at the input of the UPS, always produces a pulsating current. The coefficient remains non-zero even when using the most modern rectification and ripple suppression circuits. Therefore, a battery connected in parallel with the output of the rectifier has to supply some current at those moments in time when the current at the rectifier output decreases, and vice versa - to be recharged when the current at the rectifier output drops. This causes mini-discharge/charge cycles at a frequency typically equal to twice the operating frequency of the UPS (50 or 60 Hz). These cycles wear out the battery, heat it up and cause it to age prematurely.

In a UPS with a battery in reserve, such as a classic backup, a ferroresonant backup, or a line-interactive UPS, the battery is not exposed to ripple currents. Online UPS battery to varying degrees (depending on design features), but nevertheless is always exposed to them. To determine whether ripple currents are occurring, it is necessary to analyze the UPS topology. In an online UPS, the battery is placed between the charger and the inverter, and there will always be pulsating currents. This is the classic, “historically” earliest type of “online double conversion” UPS. If in an on-line UPS the battery is separated from the inverter input by a blocking diode, converter or switch of one type or another, then there should be no pulsating current. Naturally, in these designs the battery is not always connected to the circuit, and therefore UPS with a similar topology are usually classified as hybrid.

What you can't rely on in a UPS

The battery is the least reliable element of most well-designed UPS systems. However, the UPS architecture can affect the longevity of this critical component. If you keep the battery under continuous charging even when the UPS is turned off (as is done in all UPS manufactured by APC), its service life increases. When selecting a UPS, topologies with high battery voltage should be avoided. Beware of UPSs that expose the battery to ripple currents or overheating. Most UPS systems use the same batteries. However, design differences between UPS systems in different systems cause significant differences in battery life and, consequently, in operating costs.

Before turning on your new UPS for the first time, be sure to charge the batteries.

The batteries of the new UPS naturally lost most of their “factory” charge during transportation and storage in the warehouse. Therefore, if you immediately put the UPS under load, the batteries will not be able to provide adequate power support. Moreover, a self-test routine that automatically runs each time the UPS (except Back-UPS) is turned on, among other diagnostic operations, checks whether the battery is able to handle the load. And since an uncharged battery cannot cope with the load, the system may report that the battery is faulty and requires replacement. All you need to do in such a situation is to let the batteries charge. Leave the UPS connected to the network for 24 hours. This is the first time the batteries are charged, so it requires more time than the normal standard charging regulated in technical description. The UPS itself may be turned off. If you brought the UPS in from the cold, allow it to warm up at room temperature for a few hours.

Connect only those loads to the UPS that truly require uninterruptible power.

The use of a UPS is justified only where loss of power can lead to data loss - in personal computers, servers, hubs, routers, external modems, streamers, disk drives, etc. Printers, scanners, and especially lighting lamps do not require a UPS. What happens if the printer loses power while printing? A sheet of paper gets damaged - its value is not comparable to the cost of a UPS. In addition, a printer connected to an uninterruptible power supply device, when switching to battery power, consumes their energy, taking it away from the computer that really needs it. In order to protect equipment from discharges and interference that does not carry information that could be lost as a result of a power failure, it is sufficient to use surge protector(for example, APC Surge Arrest) or, in case of significant voltage fluctuations in the network, a network stabilizer.

If your source frequently switches to battery mode, check that it is configured correctly. It may happen that the response threshold or sensitivity is set too demanding.

Test the UPS. By periodically running a self-test, you will always be sure that your UPS is fully operational.

Do not unplug the UPS. Turn off the UPS using the button on the front panel, but do not unplug the UPS unless you are leaving it for long term. Even when turned off, the APC UPS charges the batteries.

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