The operating principle of an uninterruptible power supply. Uninterruptible power supply: purpose and specifics of operation of a household UPS. Double conversion UPS

Greetings, my dear readers! In the current Russian realities, owners of desktop computers are forced to solve problems of uninterrupted power supply. This problem can be solved using uninterruptible power supplies. Their diversity on the computer market allows you to choose a UPS to suit your specific needs. We will talk about what a UPS is and what uninterruptible power supplies there are in this article.

A UPS, or uninterruptible power supply, is a device that acts as an energy “battery”. In the event of a power outage, the UPS automatically switches the computer's power supply to power from the built-in batteries, which allows you to correctly shut down the work and save all the necessary documents.

Variety of uninterruptible power supplies

Uninterruptible power supply is your guarantee of the safety of documents and computer components as a whole. After all, if the computer is turned off incorrectly, the hard drive, motherboard, and RAM may suffer.

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

What types of UPS are there?

Uninterruptible power supplies are divided into three types:

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

Let's look at each type of uninterruptible power supply separately. This information will help you when choosing a UPS for your own needs.

Offline UPS

The operating principle of this type of power supply is to automatically switch 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 an external power source to the batteries and vice versa.

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

TO pros Such UPSs include 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 changes. This species also exhibits increased wear and tear on batteries.

Line-interactive UPS

This type of uninterruptible power supply is in most cases 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, regardless of the voltage (high or low) at the input.

Pros This type of UPS is small in size, low cost, automatic voltage regulation, and economical.

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 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 the DC is converted to a reference AC voltage and supplied to the devices.

This type is used where a reference voltage is required, and the powered devices are demanding on the quality of the power supply. Connected devices can be very different: regular workstations, file servers, network devices and other power-hungry equipment.

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

Minuses There are also: high cost, complex design, self-consumption of electricity in double conversion mode.

The first type of UPS is quite sufficient for home and office use. But if you have the financial opportunity, I would recommend the latter type to you. This is the most reliable type of protection for your computer equipment from low-quality voltage.

Main characteristics of the UPS

A UPS has several main characteristics that you should pay attention to when purchasing. Let's look at them below.

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

Typically this characteristic is indicated by the value VA or W. If the value is indicated in VA (VA), then multiply it by 0.6 to get the value in Watts that are more understandable to us.

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

These three characteristics are the most important. In addition to them, the UPS has many more characteristics. For example, when choosing a UPS 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.

Frequently encountered problems

The most important problem that most often arises with a UPS is the failure of the battery. A dead battery can be determined by the fact that the uninterruptible power supply stops supporting the load - when the power goes out, the computer immediately turns off. Also, a damaged battery can manifest itself in a different way: the uninterruptible power supply does not turn on at all, or it turns on and beeps continuously. I wrote about how to change the battery in a UPS. It says about a specific UPS, but the replacement principle is practically the same in all sources.
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 sockets.

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

Content:

The stable operation of computers and other office equipment depends entirely on the availability of power in the network to which they are connected. In the event of a power outage, the equipment will simply stop functioning. In modern conditions, this problem is easily solved by connecting an uninterruptible power supply. Therefore, many people are concerned about the question of when there is a need for a UPS for a computer: what should you pay attention to when purchasing this equipment. What parameters and criteria should be taken into account?

It is recommended to initially decide for what purposes this device is needed. If the problem is only in stabilizing the mains voltage, you can get by with simpler and cheaper ones. However, in case of regular power outages, you will definitely need a UPS, which must be selected correctly for a particular computer.

UPS use in everyday life

The main network problems include a complete lack of voltage, the presence of high-voltage impulse noise, short-term and long-term power surges, high-frequency interference and other factors that require the use of a UPS. These devices ensure uninterrupted operation of computer equipment from several minutes to one hour.

The uninterruptible power supply circuit is selected in accordance with the operating conditions, the time it takes to switch the load from the network to the battery and back, as well as the operating time of the battery itself.

UPS for home computer

Before purchasing any device, you should find out how the UPS works. Its unit contains a sensor that continuously checks the characteristics of the current in the network and the voltage level. If the parameters begin to rise or fall too quickly, it disconnects the computer from the network and immediately switches it to use a backup power source.

When switching to a backup source, the UPS emits light and sound signals. In addition, almost all UPSs have a program that allows you to automatically turn off the computer when the battery charge is depleted. When electric current appears in the network again, the sensor signals this and it switches the computer to power from the network and begins to charge the built-in battery.

The batteries used in the devices are designed for low voltage. To obtain a working value, an inverter converts it to a sinusoidal one. At the same time, the battery voltage increases and equalizes the nominal mains voltage. This way the battery is always ready for use and switches instantly when needed.

During operation, it should be taken into account that operation of the UPS at rated load is only possible for a short time. During this period, you can have time to save the data and turn off the computer correctly. Overloads are not allowed during operation; in these cases, the protection immediately turns off the device output. These problems are easily solved by increasing the battery capacity and inverter power.

Which UPS to choose for your computer

There are various types of devices for uninterruptible power supply of computer equipment. They differ in their operating principle and are divided into three main types:

Backup UPS. It is used when there is a strong voltage drop in the network or it is completely absent. In this case, the battery switches to the backup UPS. Switching occurs very quickly - within 10 milliseconds or less, which does not in any way interfere with the smooth operation of the computer. When switching during power surges, it is recommended to use a stabilizer. This will increase the battery life. When deciding how to choose an uninterruptible power supply, you should remember that this device has become widespread due to its relatively low cost, high efficiency and low noise level. The device can work offline for 5-15 minutes. When choosing and purchasing, it is recommended to create a power reserve of 20-30%.
Line-interactive UPS. The design of these devices is supplemented with a voltage stabilizer, so they are more functional and expensive. Switching to batteries occurs only in the complete absence of electricity, so the battery life is longer. In offline mode, line-interactive UPSs operate for up to 20 minutes. They are characterized by increased efficiency and a higher degree of protection. Among the disadvantages, noteworthy is the noise created by the stabilizer cooling fan.
Double conversion UPS. They belong to the category of the most complex and expensive devices. During operation, alternating current is converted to direct current, and then again to alternating current. The output voltage is 220 V and is characterized by an ideal sine wave. The batteries are always on, so no switching time is required at all. When deciding how to choose a UPS for a computer based on power, you need to take into account that these devices ensure uninterrupted operation of expensive equipment, which should not stop even for a short time. The disadvantages are low efficiency, high cost, high levels of heat and noise.

When purchasing a device, you need to pay attention to its main characteristics. The power of the UPS itself is expressed in volt-amperes (VA), and the power of the connected computer is expressed in watts (W). You can convert one value to another using a coefficient of 0.7. For example, if the device power is 1000 VA, then it will be 1000 x 0.7 = 700 W. Taking into account the power reserve, a load of up to 500 W can be connected to this UPS.

In addition, when choosing a UPS for your computer, you should pay attention to the battery life at maximum load, the presence or absence of short-circuit protection for the UPS itself and the connected equipment. It is recommended to obtain information from the seller about the possibility of replacing the battery, check the availability of the display and other specific elements.

How to choose a UPS for a computer based on power

Quite often the question arises, what power should a UPS have? The greater the computer's power consumption, the more powerful its power supply and, accordingly, the UPS must have. Most models express power not in the usual watts, but in volt-amperes.

It is quite easy to calculate the power of a UPS for a computer by multiplying the power of the monitor and power supply in watts by 1.6. Let's say that the sum of the power consumption of your monitor and power supply is 200 W. In this case, you will need an uninterruptible power supply with a capacity of 320 VA (1.6x200). For greater reliability, increase this value by another third. The result will be a value of about 400 VA. Then just look for a model with just that kind of power.

Some users have a problem calculating the power of a UPS for a computer. To do this, you need to determine the load power, which should not be higher than 70% of the UPS output power. For example, the power consumption of the processor is 65 W, the video card is 170 W, the motherboard is 40 W, the DVD drive is 20 W, the HDD is 40 W, and other equipment is 30 W. The number of possible losses is conventionally taken as 20%. Thus, the computer consumption without losses will be up to 365 W, and with losses - 438 W. Therefore, the purchased uninterruptible power supply must have a power in the range of 500-620 W.

Connecting an uninterruptible power supply for a computer

Sometimes owners of computer equipment have a question: how to install a UPS? You need to connect the uninterruptible power supply to a regular electrical outlet, and then insert the power plugs of the devices that you are going to protect from power outages into the sockets located on its body. If the uninterruptible power supply supports automatic shutdown of the computer and other control functions that are carried out using a PC, it should also be connected to the system unit, usually using a USB cable.

There are several connection options, including using one that compensates for differences from 140 to 260 volts. This method is used most often, so it should be considered in more detail. In addition to the stabilizer, you will need a surge protector. Before connecting, you need to clarify the parameters of all components. The power of the stabilizer and the UPS should be approximately equal, and the power of the UPS should be higher than the power of the computer power supply.

Connection order:

The voltage stabilizer is connected to the network, after which a surge protector is connected to it.
After this, the UPS itself is connected to the surge protector. There is a button on the body of the device that is pressed and held until the power indicator lights up.
Next, a computer is connected to the UPS, that is, a system unit and a monitor. If additional outputs are available, you can connect speakers, a printer and other equipment.

Some uninterruptible power supplies are equipped with software control, which must be configured correctly after connection. In the control panel, in the “Power Supplies” section, after installing the device, a separate UPS window will appear. It configures all the necessary parameters depending on the power of the computer and operating conditions.

The article discusses the types of UPS, the principles of operation of the UPS, and also provides real oscillograms of the output voltages.

To begin with, some general terminology. Uninterruptible power supplies (abbreviated as UPS) are also called UPS, from the English abbreviation Uninterruptable Power Supply (uninterruptible power supply). Therefore, they say both UPS and UPS, whichever is more convenient for you. In the article I will call it this way and that way.

Why do you need a UPS (UPS)

The principle of operation of a UPS is revealed in the name - it is a source whose output there is always tension. But we are technical realists gathered here, and we understand that nothing is eternal, so below we will understand the principle of action.

UPSs are mainly used where a power failure can cause negative consequences. For example, power supply for computers and servers, power supply for communication and signal distribution devices (routers), power supply for devices whose automatic reboot (restart) is impossible without human intervention.

How my reader modified the UPS for a strategically important system (2 servers, etc.). In addition, I improved the circuit and added the ability to use a regular car battery.

For household items, these are primarily computers and heating systems.

It should be understood that UPSs are selected for a load operating time of 10-15 minutes, rarely up to half an hour. It is assumed that during this time the power will appear, or the person (operator) will take the necessary actions (save the data, call the enterprise’s energy service, complete the technological process).

The UPS should not be considered as a backup power source. It is only an emergency source, and at best is used very rarely, for a total of no more than 10 minutes per year (several times, for a period of no more than a minute). If this time is longer, then you should think about improving the quality of the power supply.

A backup power source can be considered those sources that can completely replace the main power supply for a long time, from several hours to several days. This could be another line (see article about), a wind generator. Theoretically, a UPS can serve for these purposes, but this requires batteries of huge capacity, which will significantly affect the price of such a system.

Types of uninterruptible power supplies

Types (types) of UPS have many names, but there are still exactly three of them. Let's figure it out.

So, there are three main types of UPS:

Back UPS

Other equivalent names are Off-line UPS, Standby UPS, standby UPS. The most common UPS are used for most types of household and computer equipment.

Back simply switches the load to battery power when the input voltage goes out of range. The lower limit for different models is about 180V, the upper limit is about 250V. Transitions to the battery and back are with hysteresis. That is, for example, when decreasing, the transition to the battery will take place at 180 V or less, and back at 185 V or more. The same principle applies to all types of UPS.

Reminds me something of which disables load, but Back UPS does not disconnect, but switches on the battery, which allows it to work for some time.

Smart UPS

Other names: Line-Interactive, interactive type UPS. The principle of operation is not far removed from Back.

Smart UPS operate smarter, as the name suggests. They also additionally switch the internal autotransformer, in a sense stabilizing the input voltage. And only as a last resort do they switch to a battery.

Thus, the output voltage norm is maintained even with larger deviations at the input (150...300V). The autotransformer has several switching stages, so the Smart UPS switches the autotransformer terminals until the last moment, turning on the battery only at the last moment. This allows you to save the battery by turning it on only when there is a complete power failure.

This device resembles the stepwise switching of the windings of an autotransformer. The only difference is that when it goes beyond the operating limits, the stabilizer will be powerless, and our “clever girl” will put the battery into operation, and the power will not be lost.

Online UPS

Other names: online, double conversion uninterruptible power supply, inverter. A completely different principle of operation, for lovers of pure sine. The energy from the input is converted into direct voltage and supplied to the inverter, which generates pure sine wave. And at the same time, it maintains the battery at 100% readiness. If necessary, the inverter continues to operate in the same way, only it receives power from the battery.

Used for emergency power supply of equipment that is sensitive to the shape of the output voltage - for example, gas boilers, servers, professional audio-video equipment and other strategically important equipment.

There are two disadvantages of online UPS - price and efficiency. The efficiency is low, because such a UPS is constantly on, as the name suggests. Unlike the other two types.

There are varieties of online UPS that use the so-called “through zero” for the correct operation of gas electric boilers. This is due to the fact that such boilers are sensitive to the presence of real zero for proper ignition.

Examining a UPS using an oscilloscope

And now - the most interesting part.

Output voltage Back UPS

I conducted a study using a Fluke 124 oscilloscope. I present and comment on the oscillograms (the shape of pulses and oscillations at the ups output) below.

What can you see from this timing diagram? Period 20ms, frequency 50Hz, amplitude 315V. It is worth noting that the phase of the sine and the generated pulses coincides, which is good. When the mains voltage fails, the UPS hesitates for 5-7 ms, and then there are pulses called “quasi-sine”. Here they are:

Back UPS. Output voltage when powered by batteries.

The oscilloscope measured the RMS voltage (root mean square), it corresponds to the norm. However, when I measured the same voltage with a multimeter, I got a value of 155 V. Why is the UPS output low voltage?

The fact is that the multimeter only measures the first harmonic with a frequency of 50 Hz. For sinus everything is smooth. But if you measure the voltage of such pulses, it is necessary to measure RMS, root mean square, otherwise the following harmonics will not be taken into account - 100, 150, 200 Hz. And they make up a significant part of the energy, up to 30%. UPS manufacturers know this feature, and in order not to bother (and not to increase the price of their products), they issue such pulses with an amplitude of about 370V to our devices.

Learn more about measuring root mean square non-sinusoidal voltage in the video:

Here is an enlarged graph, where you can see that the voltage after switching first increases for half a second to 400V, and then stabilizes:

Back UPS. Exit, duration 2 seconds

And here’s how the voltage shape changes at the Back-UPS output when switching from battery to mains power:

Back UPS, – Voltage at the UPS output when switching from battery to mains. Ups output pulse shape

The phase also does not change, everything is fine. I connected a UPS to the output, switched power modes back and forth - the starter was pulled in reliably, no problems.

The test subject was an APC Back-500-RS UPS, parameters in the photo below:

Back UPS parameters - rear panel

Smart UPS output voltage

Now, for the sake of completeness, I will give an oscillogram of the voltage at the output of the Smart UPS. The UPS Ippon Smart Power Pro 1000 was tested.

Smart UPS_Network-battery

The switching time is also insignificant for all modern equipment - less than 7 ms.

I did not smoothly change the input voltage, since there was no such goal. I believe that in this case the Smart UPS behaves exactly the same as a relay voltage stabilizer.

These studies were carried out as part of a project on an industrial refrigerator.

In order to protect electrical appliances from power outages, an uninterruptible power supply is used. It is much more profitable to buy such a device once than to constantly repair broken equipment or buy a new one. There are differences in UPS power, size, and availability of additional functions.

Types of UPS

The power of the system protected from voltage surges may vary, so when choosing a UPS, this parameter must be taken into account. If you only need to protect your computer, then there is no point in buying an expensive and powerful UPS, since it will not use its capabilities and will become an additional consumer of electricity. For a home computer, a device with a power of less than 1 kVA will be sufficient, while for an office where there are many peripheral devices, such a solution will not be suitable.

If the total connected power is higher than the power of the UPS, it will simply turn off, and accordingly all equipment will turn off. The power of the device will also affect its characteristics such as weight and dimensions. They also need to be taken into account so that it is possible to install the device in the chosen location and it does not interfere with you.

To select an uninterruptible power supply based on power, you need to add up the power of all connected devices and add 20-30% of the reserve to it. This will allow you to add or remove some equipment and will not affect the operation of the uninterruptible power supply.

There are three types of UPS:

Offline (Standby). This is the simplest device, which is a surge protector with a voltage converter and has a small battery. Such equipment is capable of ensuring the operation of connected devices after a power outage for 3-25 minutes. This is quite enough to save information and turn off the computer.

Line-Interactive. This is the most common equipment. It has an automatic voltage control system, which turns on the battery not only when the power is turned off, but also during power surges.

Online (On-Line). This is the most efficient UPS, but it also has the highest cost. It has a complex structure: transformer, inverter, voltage rectifier. In this case, there are no delays when switching to the battery. Such equipment is professional and is used to protect servers and corporate networks.

UPS device

The design of an uninterruptible power supply will differ for different types. If we talk about its simplified circuit, then such equipment consists of a battery and special devices that compensate for voltage drops in the network. It contains a rectifier, an inverter and a filter; some models may have Bypass(bypass).

The main element, no matter what type of UPS, will be. It is its power that will determine how long the connected equipment can operate after a power outage. Usually the uninterruptible power supply has lead-acid batteries. Their parameters: voltage 12 V and capacity 7-9 Ah. These batteries are sealed and cannot be serviced. The simplest off-line models have only one battery, while powerful devices have many more. There may also be gel batteries; if lead-acid batteries have a service life of 6-10 years, then helium batteries have a service life of 10-15 years.

Principle of operation

An uninterruptible power supply has the following principle of operation: when the voltage in the network disappears or its parameters go beyond acceptable limits, and phase imbalance and frequency changes occur, it automatically switches power to the connected equipment from its battery. The battery powers an inverter, which converts its DC voltage into AC voltage.

Some UPSs have software that allows you to remotely monitor the battery charge level and the voltage at the device output. In the case when a computer or server is powered by a UPS and its battery charge level becomes critical, the programs in use are terminated and all devices are turned off.

Application of uninterruptible power supplies

Protection of connected equipment from small and short power outages.
Noise reduction and filtering of impulse disturbances occurring in the network.
Power supply to connected devices for a certain period of time.
Overload and short circuit protection.

Devices with a more complex design have a number of additional functions:

The ability to automatically turn off connected equipment during long power outages, as well as reboot it after power is restored.
Monitoring and monitoring of the main parameters of the device and its performance.
Display of UPS parameters and mains parameters.
In case of emergency situations, automatic alarm.
The presence of a timer allows you to configure parameters for turning off and turning on connected devices.

In addition to protecting your computer, an uninterruptible power supply can be used to protect various household appliances.

How to chooseuninterruptable power source

The UPS can be installed at one workstation, for an office or for a large server station. When choosing it, the time required to correctly turn off the equipment is taken into account. For one computer, a line-interactive UPS will be sufficient. It ensures that the computer operates for a period of time that is sufficient to shut down correctly and protect the computer from failure.

For an office or server station, it is best to purchase online UPSs that can power the connected equipment for a long period of time.

When choosing a UPS, study its rating data and choose a power that will provide the required battery life. You cannot install additional batteries yourself if this is not provided for the specified device.

To protect not only your computer, but also your data, you must use a UPS with software. It allows you to monitor the state of the network and in case of long-term failures, open programs and all data are automatically saved, so there is no loss of information.

It is convenient when the UPS has not one, but several sockets, which allows you to connect several consumers at once. The presence of light and sound indication will signal the transition to offline mode. It’s even more convenient when there is a display that displays all the necessary information.

It is necessary to purchase devices that have the ability to replace the battery, since its service life is limited; if this is not possible, then you will have to buy a new UPS, and this is expensive.

Advantages and disadvantages

Advantages of online UPS:

Possibility of regulation and stabilization of voltage and current frequency.
The switchover time to offline mode occurs without delay and therefore the consumer does not notice when this occurs.

Flaws:

Due to the fact that double conversion is performed, electricity is lost.
It has a complex device.
It works constantly, so there is a certain level of noise.
During its operation it creates electromagnetic interference.

Offline UPS is in standby mode and starts working as soon as a fault appears in the network.

Main advantages:

Higher efficiency.
Since it only works in case of an accident and to recharge the battery, it makes much less noise.

The disadvantage of such equipment is that when switching to offline mode, there is a short pause, usually 20 ms, during which time a voltage surge may occur. In addition, these devices cannot regulate such indicators as voltage and frequency.

Interactive The uninterruptible power supply operates in standby mode, but it has an autotransformer that regulates the voltage. When voltage changes cannot be corrected by the transformer, the UPS switches to battery power.

Advantages:

The transition is smoother than offline, but there is still a delay, it is about 5 ms.
Possibility of voltage stabilization.
Monitors and records power grid indicators.

The disadvantage of such equipment is that it cannot regulate the frequency of the current and if the output is rectangular pulses, it has the same time delay as an offline UPS.

In order for the uninterruptible power supply to serve for a long time and reliably, you must adhere to the following recommendations:

On average, the service life of a UPS is 4-6 years, and in ideal conditions, it can reach 10-12 years.
The service life is negatively affected by frequent complete discharge of the battery and its severe overload.
If the device is not in use, the battery must be stored in a charged state and recharged once every 3-4 months.
Before turning on the new UPS for the first time, it is necessary to charge the battery, since it discharges during storage, then everything happens automatically.
You cannot buy a new battery for future use, as it has a certain shelf life.
To prevent device calibration failure, it is necessary to promptly change failed batteries.
If the device is brought in from the cold, it is necessary that it warms up to room temperature.
From time to time, you need to perform self-tests on your equipment.
Rechargeable batteries can only be replaced with batteries of the same type.

Due to the fact that the quality of power in our electrical networks is not the best and power outages often occur, purchasing and installing a UPS will help protect equipment from failure and make it possible to continue working during a short-term power outage.

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 of devices, which 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 - how long the battery life will last);
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. The inverter that converts direct current from the battery into alternating current output is one of the simplest installed in this type of UPS, so the waveform does not correspond to 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.

The principle diagram of the operation of line-interactive UPS includes AVR - a module for automatically adjusting the 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 best type of 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 characteristics of a 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 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, such as a WiFi router, cannot be connected 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 an electric power cable, but also in the event of various accidents and breakdowns - both via a 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.

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