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Uninterruptible power supply: purpose and types. Uninterruptible Power Supplies: Attempt to Develop a Comprehensive Test Method Uninterruptible Power Supply Can be Used

Before buying a new UPS, you should familiarize yourself with some of the "internal" aspects of its operation. And to ensure that your uninterruptible power supply will serve you as long as possible and your investment is as effective as possible, try to follow the tips below.

What batteries are used in the UPS

All UPSs manufactured by APC (and other well-known large UPS manufacturers) use lead acid rechargeable batteriesvery similar to the most common car batteries. The difference is that if we are to make such a comparison, then the batteries used by APC are made according to 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" as you like, without fear of spilling electrolyte.

How long lasting are UPS batteries

Although different UPSs use seemingly the same battery technology, there is wide variation in battery life from different manufacturers. This is very important for users as battery replacement is expensive (up to 30% of the original UPS cost). Battery failure reduces system efficiency and is a source of downtime and unnecessary headaches. Battery reliability is significantly affected by temperature. The fact is that the natural processes that cause battery aging are largely temperature dependent. Detailed test data provided by battery manufacturers show that battery life is reduced by 10% for every 10 ° C increase in temperature. This means that the UPS must be designed to minimize battery heating. All online UPSs and online hybrid sources run hotter than standby or line-interactive UPSs (which is why the fan is required first). This is the most important reason why standby and line-interactive UPSs require battery replacement less often than UPSs with online topology.

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

The charger is an essential component of the UPS. The conditions for recharging batteries have a significant impact on their longevity. UPS battery life is maximized when it is continuously recharged from a constant voltage or floating type charger. In fact, the life of a rechargeable battery is much longer than simple storage. This is because some of the natural aging processes are inhibited by constant recharging. Therefore, it is necessary to recharge the battery even if the UPS is off. In many cases, the UPS is switched off regularly (if the protected load is disconnected, then there is no need to keep the UPS switched on, as it can trip and cause unwanted battery wear). Many of the commercially available UPSs do not provide an important trickle charge function.

Does voltage affect reliability?

The batteries are made up of individual cells, approximately 2V each. To create a higher voltage battery individual elements 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 at the same time. Due to the inevitable scatter of parameters, some cells take a larger share of the charging voltage compared to 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 elements fails, the battery as a whole fails. It has been proven that the rate of aging processes is directly related to the number of cells in the battery; therefore, the aging rate increases with increasing battery voltage. IN best types The UPS uses fewer more powerful elements instead of more elements of lower capacity, thereby achieving increased reliability. Some manufacturers use high voltage batteries, which at a given power level can reduce the number of wiring and semiconductors, thus 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 UPS, 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 in APC batteries is 3-5 years (depending on temperature conditions, frequency of discharge / charge cycles), while some manufacturers indicate a service life of only 1 year. Over a 10 year UPS life, some users spend twice as much on batteries as they do on the unit! Although it is easier and cheaper for the manufacturer to design a UPS using high-voltage batteries, the user incurs hidden costs in the form of a shorter UPS life.

Why "ripple" current decreases battery life

Ideally, the UPS battery should be kept on a float or trickle charge at all times to maximize usage time. In this situation, a fully charged battery draws a small amount of current from the charger, called float current, or self-charging current. Despite the recommendations of the battery manufacturers, some UPS systems additionally expose the batteries to ripple currents. Ripple currents occur because the inverter supplying AC power to the load draws DC current at the input. The rectifier at the input of the UPS always produces a ripple current. The coefficient remains non-zero even with the most advanced rectification and ripple suppression circuits. Therefore, the battery connected in parallel with the output of the rectifier has to give some current at those times when the current at the output of the rectifier decreases, and vice versa, it must be recharged when the current at the output of the rectifier drops. This causes mini discharge / charge cycles at a rate 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 prematurely age.

In a UPS with a battery in standby, such as classic standby, ferroresonant standby, line-interactive, the battery is not subject to ripple currents. Online UPS batteries vary in degree (depending on design features), but are nevertheless always exposed to them. To find out if there are ripple currents, 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 ripple currents. This is the classic, historically the earliest type of online double conversion UPS. If, in an on-line UPS, the battery is separated from the input of the inverter by a blocking diode, converter or switch of one type or another, then there should be no ripple current. Naturally, in these designs, the battery is not always connected to the loop, and therefore a UPS with a similar topology is usually referred to as a hybrid.

What you can't rely on in a UPS

The battery is the least reliable element in most well-designed UPS systems. However, the UPS architecture can affect the longevity of this critical component. Keeping the battery on trickle charge even when the UPS is turned off (as is done in all APC UPSs) will increase its useful life. When choosing a UPS, high battery voltage topologies should be avoided. Beware of UPS where the battery is exposed to ripple currents or overheating. Most UPS systems use the same batteries. Yet design differences between UPS systems in different systems cause significant differences in battery life, and therefore in operating costs.

Always charge the batteries before using a new UPS for the first time.

The batteries of the new UPS, naturally, lost most of the "factory" charge during transportation and storage in the warehouse. Therefore, if you put the UPS under load immediately, the batteries will not be able to maintain the power as required. Moreover, a self-test routine that runs automatically every time the UPS (excluding 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 needs to be replaced. All one has to do in such a situation is to let the batteries charge. Leave the UPS plugged in for 24 hours. This is the first time the batteries are charged, so it takes more time than regular regular charging as specified in the technical description... The UPS itself may be turned off. If you brought the UPS from a cold place, let it warm up at room temperature for several hours.

Connect only the loads to the UPS that really require uninterruptible power supply

The use of a UPS is justified only where loss of power can lead to the loss of data - in personal computers, servers, hubs, routers, external modems, tape drives, floppy drives, etc. Printers, scanners, and even more so lighting lamps do not need a UPS. What happens if the printer loses power while printing? A sheet of paper will deteriorate - its value is not comparable to the cost of a UPS. In addition, a printer connected to an uninterruptible power supply, when switching to battery power, consumes battery power, taking it away from the computer that really needs it. In order to protect against discharges and interference equipment that does not carry information that may be lost as a result of a power failure, it is enough to use a power filter (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 if it is configured correctly. It may be that the response threshold or sensitivity is set too demanding.

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

Do not unplug the UPS from the wall outlet.Turn off the UPS using the button on the front panel, but do not unplug the UPS cord from the outlet unless you are leaving it on long term... Even when turned off, the APC UPS is charging the batteries.

ComputerPress 12 "1999

Greetings to you my dear readers! In the current Russian realities, the owners of stationary computers are forced to solve the problems of uninterrupted power supply. Decide this problem possible using uninterruptible power supplies. Their variety in the computer market allows you to choose a UPS for your specific needs. We will talk about what a UPS is and what kinds of uninterruptible power supplies are in this article.

A UPS, or uninterruptible power supply, is a device that acts as a "battery" for energy. In the event of a power failure, the UPS automatically switches the computer to power from the built-in batteries, allowing you to shut down gracefully and save all the documents you need.

Variety of uninterruptible power supplies

Uninterrupted is your guarantee of the safety of documents and computer components as a whole. Indeed, if the computer is turned off incorrectly, it can suffer and hDDand motherboard, and RAM.

We figured out what an uninterruptible power supply is. Let's move on to the next question.

What kind of UPS are there?

Uninterruptible power supplies are divided into three types:

Offline UPS;
Line-interactive UPS;
Online UPS (double conversion UPS).

Let's consider separately each type of UPS. This information will help you when choosing a UPS for your own needs.

Offline UPS

Principle of operation of this type power supply consists in automatically switching the computer or other connected device to power from the built-in batteries when disconnected from the external power supply.

Often a mechanical relay acts as a switch, so you may hear a clicking sound when the UPS switches from external power to batteries and vice versa.

This type has become widespread among ordinary users and in offices.

TO pluses such UPSs can be attributed to simplicity, compactness and low cost. The main minus is the impossibility of stabilizing the input voltage, and therefore your computer will not be protected from sudden voltage surges. Also, this species has an increased wear of batteries.

Line Interactive UPS

In most cases, this type of uninterruptible power supply is used to protect network and other telecommunications equipment, as well as groups of computers.

The main feature of these sources is the ability to adjust the output voltage without connecting to batteries, no matter what the voltage (high or low) is at the input.

Pluses this type of UPS are small size, low cost, automatic adjustment stress, efficiency.

But he also has minuses - this is a relatively long switching to batteries, the impossibility of adjusting the shape of the output voltage when operating from an external power supply, the change in the output voltage occurs in steps.

Double conversion UPS

This type of UPS performs voltage conversion twice: the input AC voltage is converted to DC, and then DC is converted to a reference AC voltage and supplied to the devices.

Applicable given view where a reference voltage is required, and the powered devices are demanding on the quality of the power supply. The connected devices can be very different: ordinary workstations, file servers, network devices and other power-demanding equipment.

pros the online UPS has essential: full control of the input and output voltage, zero waiting time for switching to batteries, connected equipment does not affect the external power grid in any way.

Minuses are also available: high cost, complex design, electricity consumption "by itself" in double conversion mode.

The first type of UPS is enough for home and office. But if there is a financial opportunity, then I would recommend you the latter type. This is the most reliable type of protection for your computer equipment from low-quality voltage.

Main characteristics of the UPS

A UPS has a few basic features to look out for when buying. Let's consider them below.

Power... This characteristic directly determines what equipment can be connected to this UPS. Always choose a source with a power reserve. This will avoid possible problems with a lack of power.

Usually this characteristic is indicated by the value of VA or W. If the value is indicated in VA (VA), then multiply it by 0.6 to get the value in watts more understandable to us.

UPS type... I talked about the types of uninterruptible power supplies above. We came to the conclusion that a double conversion UPS would be the most optimal, but an offline or line-interactive source would be sufficient for home needs.
Battery life... This value is very important, since it determines how long the computer will work without external power supply. Usually the time autonomous work set in the range of 5-30 minutes. Please note that when the UPS is at maximum load, the operating time without electricity is significantly reduced.

These three characteristics are the most important. Besides these, the UPS has many more characteristics. For example, when choosing an uninterruptible power supply in a store, pay attention to what power connectors are installed in the source, whether there is a display and additional interfaces (RJ-11, USB), how many batteries are installed, and others.

Frequent problems

The most important problem that a UPS most often encounters is the failure of the battery. A dead battery can be determined by the fact that the uninterruptible power supply ceases to hold the load - when the power goes out, the computer immediately turns off. Also, a damaged battery can manifest itself differently: the UPS does not turn on at all, or it turns on and beeps continuously. I wrote about how to change the battery in an uninterruptible power supply in. It says about a specific UPS, but the principle of replacement in all sources is practically the same.
The UPS may not turn on at all due to a blown fuse.
If the uninterruptible power supply starts normally, but the computer does not turn on, then check the wires, they may come out of the jacks.

I hope my article was useful for you and you learned something new for yourself. If you still have questions, you can ask them in the comments.

What batteries are used in the UPS

All UPSs manufactured by APC (and other well-known major UPS manufacturers) use lead-acid batteries, very similar to most common car batteries. The difference is that if we are to make a similar comparison, then the batteries used by APC are made according to 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" as you like, without fear of spilling electrolyte.

How long lasting are UPS batteries

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

Does voltage affect reliability?

The batteries are made up of individual cells, approximately 2V each. The individual cells are connected in series to create a higher voltage battery. 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 at the same time. Due to the inevitable scatter of parameters, some cells take a larger share of the charging voltage compared to 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 elements fails, the battery as a whole fails. It has been proven that the rate of aging processes is directly related to the number of cells in the battery; therefore, the aging rate increases with increasing battery voltage. The best types of UPS use fewer more powerful elements instead of more elements of lower capacity, thereby achieving increased reliability. Some manufacturers use high voltage batteries, which at a given power level can reduce the number of wiring and semiconductors, thus 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 UPS, 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 in APC batteries is 3-5 years (depending on temperature conditions, frequency of discharge / charge cycles), while some manufacturers indicate a service life of only 1 year. Over a 10 year UPS life, some users spend twice as much on batteries as they do on the unit! Although it is easier and cheaper for the manufacturer to design a UPS using high-voltage batteries, the user incurs hidden costs in the form of a shorter UPS life.

Why "ripple" current decreases battery life

What you can't rely on in a UPS

Always charge the batteries before using a new UPS for the first time.

The batteries of the new UPS, naturally, lost most of the "factory" charge during transportation and storage in the warehouse. Therefore, if you put the UPS under load immediately, the batteries will not be able to maintain the proper level of power. Moreover, a self-test routine that runs automatically every time the UPS (except Back-UPS) is turned on, among other diagnostic operations, checks whether the battery is able to cope with the load. And since an uncharged battery cannot cope with the load, the system may report that the battery is faulty and needs to be replaced. All one has to do in such a situation is to let the batteries charge. Leave the UPS plugged in for 24 hours. This is the first time the batteries are charged, so it takes longer than the regular charging described in the datasheet. The UPS itself may be turned off. If you brought the UPS from a cold place, let it warm up at room temperature for a few hours.

Connect only the loads to the UPS that really require uninterruptible power supply

The use of a UPS is justified only where loss of power can lead to loss of data - in personal computers, servers, hubs, routers, external modems, tape drives, floppy drives, etc. Printers, scanners, and even more so lighting lamps do not need a UPS. What happens if the printer loses power while printing? A sheet of paper will deteriorate - its value is not comparable to the cost of a UPS. In addition, a printer connected to an uninterruptible power supply, when switching to battery power, consumes battery power, taking it away from the computer that really needs it. In order to protect against discharges and interference equipment that does not carry information that may be lost as a result of a power failure, it is enough to use a power filter (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 if it is configured correctly. It may be that the response threshold or sensitivity is set too demanding.

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

Do not unplug the UPS from the wall outlet.Switch off the UPS using the button on the front panel, but do not unplug the power cord unless you are leaving it for a long period. Even when turned off, the APC UPS is charging the batteries.

ComputerPress 12 "1999

Power quality requirements are legally prescribed state standards and quite strict regulations. Electricity supplying organizations make a lot of efforts to comply with them, but they are not always implemented.

In our apartments, and in production, periodically there are:

complete power outages for an indefinite period;

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

surges and voltage drops with different duration;

high-frequency noise pads;

frequency drifts.

All these malfunctions negatively affect the work of residential and office electricity consumers. Particularly affected by the quality of power supply are microprocessor and computer devices, which not only fail, but can also completely lose their performance.

Purpose and types of uninterruptible power supplies

To reduce the risks of power supply faults electrical network are used backup devices, which are commonly called uninterruptible power supplies (UPS) or UPS (derived from the abbreviation of the English phrase "Uninterruptible Power Supply").

They are manufactured in different designs to meet specific customer needs. For example, powerful UPSs with helium batteries are able to keep an entire cottage on power for several hours.

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

When the external source is disconnected, 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 can only complete the computer emergency shutdown program. Moreover, the duration of the entire process of their work will not exceed 9-15 minutes.

Computer uninterruptible power supplies are:

built into the device case;

external.

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

Laptop battery with built-in controller is an uninterruptible power supply. Its scheme in automatic mode protects operating equipment from power failures.

UPS external structuresdesigned for the normal completion of programs stationary computerare manufactured in a separate block.

They are connected via network adapter plug into an electrical outlet. Only those devices that are responsible for the operation of programs are powered from them:

system unit with a connected keyboard;

monitor displaying ongoing processes.

Rest peripherals: scanners, printers, acoustic speakers and other equipment is not powered by UPS. Otherwise, in the event of an emergency termination of programs, they will take on part of the energy stored in the batteries.

Options for building UPS operating circuits

Computer and industrial UPS are manufactured in three main options:

power supply redundancy;

interactive scheme;

double conversion of electricity.

In 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 the 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 the external power supply disappears or goes beyond the established standards, the controller directs the battery energy to power the consumers. A simple inverter is connected to convert DC to AC.

UPS Standby Benefits

Uninterruptible power supplies of the Off-Line circuit have high efficiency, when the voltage is applied to them, they operate quietly, generate little heat and are relatively cheap.

disadvantages

UPS Standby stand out:

long transition to battery power 4 ÷ 13 ms;

a distorted form of the output signal produced by the inverter in the form of a square wave, and not a harmonic sinusoid;

lack of voltage and frequency adjustment.

Such devices are most common on personal computers.

UPS interactive circuit

They are designated by the English term "Line-Interactive". They are performed according to the previous, but more complicated scheme by turning on a voltage stabilizer using a step-controlled autotransformer.

This provides a correction for the value of the output voltage, but they are not able to control the signal frequency.

Noise filtering in normal mode and the transition to inverter power in case of emergencies occurs according to the UPS Standby algorithms.

Adding a voltage regulator different models with control techniques allowed to create inverters with a waveform of not only a square wave, but also a sinusoid. However, a small number of control stages based on relay switching does not allow full stabilization functions.

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

In expensive models, inverters operate on semiconductor switches. UPS Line-Interactive have a faster transition to battery power than Off-Line UPS. It is provided by the operation of the synchronization algorithms between the input voltage and the output signals. But at the same time, there is some underestimation of the efficiency.

Line-Interactive UPS cannot be used to power induction motors that are massively installed throughout household appliances, including heating systems. They are used to operate devices with 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 operates on equipment that requires high quality power supply. It performs double conversion of electricity when sinusoidal harmonics alternating current are constantly converted by the rectifier to a constant value, which is passed through the inverter to create a repeated sine wave at the output.

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

The operation of the UPS On-line according to the battery condition can be divided into three stages:

charging stage;

waiting state;

discharge on the computer.

Charge period

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

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

Ready period

After the end of the battery charging, the automatic power supply unit closes the internal switch.

The battery maintains a standby state.

Discharge period

The battery is automatically transferred to the power supply of the computer station.

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

UPS On-line is able to correct not only the voltage value, but also its oscillation frequency. This distinguishes them favorably from previous models and allows you to use to power various complex devices with induction motors. However, the cost of such devices is much higher than previous models.

UPS composition

Depending on the type working scheme The uninterruptible power supply kit includes:

accumulators for accumulating electricity;

Ensuring maintenance of the battery performance;

inverter for sine wave formation,

process control scheme;

software.

For remote access to the device can be used the local network, and it is possible to increase the reliability of the circuit due to its redundancy.

In separate uninterruptible power supplies, the "Bypass" mode is used, when the load is powered by the filtered mains voltage without the operation of the main circuit of the device.

Part of the UPS has a “Booster” step voltage regulator, controlled by automatic equipment.

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

Uninterruptible Power Supply, UPS, UPS - as soon as this simple device is not called, capable of providing uninterrupted power supply at facilities of particular importance. These facilities, first of all, include nuclear energy enterprises, oil production, oil refining complexes and social infrastructure facilities.

Equally important is uninterrupted power supply and at home: effective work local computer networks and personal computers are directly dependent on electricity. In the event of a power outage or when it is completely disconnected, it will allow the computer to work for several tens of minutes, which is enough to save the necessary data and safe shutdown computer.

It is clear that uPS prices for one computer and uPS prices for large production will differ from each other. Therefore, choosing UPS /UPS, you need to know about certain types of such devices.

UPS classification and types

Based on various parameters, UPS it is customary to divide into several types. If power is used as the determining factor UPS, then among them there are high, medium and low power... One or another power class is used for various purposes, and it is clear that using a power of several hundred watts will not be entirely advisable at home for one computer.

Another classifying parameter defining types UPS, it is considered to be the principle of operation of the uninterruptible power supply systems themselves. In this regard, such categories are distinguished. UPS as online (on-line), offline (off-line) and line-interactive (line-interactive).

Offline uninterruptible power system provides connection to the mains supply during normal operation. In emergency mode, the power is switched to backup sources, in this case to the batteries. The main advantage UPS the offline type remains its simplicity of execution and unpretentiousness in work.

Line-interactive UPS in addition to the switching device, they include an input voltage stabilizer. I.e uninterruptible power system this type not only provides autonomous power supply devices during a power outage, but also protects against undervoltage or overvoltage without a general switch to emergency mode.

Online uninterruptible power system built on the principle of double voltage conversion. The AC voltage arriving at the input is transformed into a DC voltage by means of a rectifier, and then by means of an inverter it becomes AC again. All this contributes to the establishment of a stable level of the output voltage, and also suppresses the interference of the main supply network.

Type