Uninterruptible power supply unit: the purpose and specifics of the operation of a household UPS

Line Interactive

Line interactive ups models are equipped with stabilizers that work all the time and provide an infrequent connection of batteries.

The device interacts with the network by controlling the amplitude and shape of the mains voltage.

When the voltage decreases or increases, the unit corrects its value by switching the taps of the autotransformer. In this way, its nominal value is maintained.If the parameter is out of range and the switching range is no longer sufficient, the UPS switches to battery backup. The unit can be disconnected from the main power when a distorted signal is received. There are models that correct the voltage shape without switching to battery operation.

Disadvantages of Line Interactive UPS

Despite all the advantages, more modern types of UPS (online UPS) are superior to line-interactive devices. In contrast, the category under consideration has the following disadvantages:

• Slow switching to operating mode from built-in batteries. Line interactive takes about 4-6 ms to switch to batteries. This is a pretty significant gap. Therefore, it is unacceptable to connect load-sensitive devices to the source. Line-interactive uninterruptible power supplies cannot ensure the stable operation of most household appliances, heating equipment, etc.
• Rough stabilization. The considered type of uninterruptible power supplies provides voltage stabilization at a rather primitive level. Most often, this is an autotransformer with 2-3 stages, switching between which is carried out using a relay.

Types of "uninterruptibles"

There are three basic types of UPS.

1. Redundant UPS (standby, offline, back-ups). The simplest and cheapest technical solution (for example, the popular APC Back-UPS CS 500). In case of a significant overvoltage or undervoltage, the UPS is disconnected from the 220V network and switches to battery mode. The main elements of an offline UPS: batteries (battery), charger, inverter, step-up transformer, control system, filter (Fig. 1).
   a)
   b)
   Rice.1 Normal operation (a) and battery operation (b) The advantage of an offline UPS is its low cost and high efficiency when operating from the mains. Disadvantages: a high level of output voltage distortion (high harmonics, ≈30% in the case of a square wave), the inability to adjust the input voltage parameters. The characteristics of the output voltage will be discussed in more detail below.).
2. Interactive UPS (English line - interactive). It is an intermediate type between a cheap and simple offline UPS and an expensive multifunctional online UPS (for example, ippon back office 600). Unlike the offline UPS, the interactive source has an autotransformer that allows you to maintain the output voltage level within 220V (+ -10%) during mains voltage drops / increases (Fig. 2). As a rule, the number of voltage levels of an autotransformer ranges from two to three.
   (a)
   (b)
   (in)
   (G)
   Rice. 2 The operation of the interactive UPS at normal mains voltage (a), during a mains voltage drop (b), with increased mains voltage (c), with a mains voltage failure or a significant increase (d) The output voltage is adjusted by switching to the corresponding tap of the transformer winding. With a deep drawdown or a significant increase or complete disappearance of the mains voltage, this class of UPS functions similarly to the offline class: it disconnects from the network and generates an output voltage using battery power. Regarding the shape of the output signal, it can be both sinus and rectangular (or trapezoidal).
   The advantages of line-interactive in comparison with a standby UPS: less time for switching to battery backup, stabilization of the output voltage level. Disadvantages: lower efficiency in mains operation, higher price (compared to offline type), poor surge filtering (surge).
3. Double conversion UPS (English double-conversion UPS, online). The most functional and expensive type of UPS. The bespereboynik is always included in a network. The input sine current is passed through the rectifier, filtered, then inverted back to AC. A separate DC/DC converter can be installed in the DC link. Since the inverter is always in operation, the delay to switch to battery mode is practically zero. Stabilization of the output voltage during drawdowns or dips in the mains voltage is better, in contrast to the stabilization of the line - interactive UPS. The efficiency can be in the range of 85%÷95%. The output voltage is often sinusoidal (harmonic <5%).
   Rice. 3 Functional diagram of one of the online UPS options. 3 shows a block diagram of the online UPS option. The mains voltage is rectified here by a semi-controlled rectifier. The impulse voltage is filtered and then inverted. In online UPS circuits, there may be one or more so-called bypasses (bypass switches). The function of such a switch is similar to the function of a relay: switching the load for battery power or directly from the network.
   Based on the online structure, not only low-power single-phase, but also industrial three-phase UPSs are created.The continuity of the power supply of large file servers, medical equipment, telecommunications is carried out exclusively on the basis of the online structure of the UPS.
4. Special types of UPS. Other specific UPS types are also used. For example, a ferroresonant uninterruptible power supply. In this UPS, a special transformer accumulates a charge of energy, which should be enough for the time of switching the power supply from the network to the batteries. Also, some UPSs use the mechanical energy of a super flywheel as a power source.

UPS faults description

If the UPS fails, all equipment is at risk, so you should know how to check the UPS and its battery for functionality. Methods for eliminating minor malfunctions are necessarily described in the user manual for the device, therefore it is recommended that you study it first. If this does not work, you should try to determine the problem yourself.

Beeps continuously

The UPS beeps when there is a power outage and the equipment has switched to battery power. In this case, everything is fine. It is for these purposes that this device was created. It is enough for the user to shut down the entire system and turn off the power of the device.

In the event that such a squeak occurs regularly, while there is voltage in the network, it may be necessary to test the electrical network and understand the causes of power surges. In this case, the uninterruptible power supply is not to blame, the problem is elsewhere.

Pay attention to the device indicators

Another reason for UPS squeaking is overload. In this case, the device does not pull the equipment connected to it. It is possible to calculate the source of problems by connecting and disconnecting devices one by one.The solution to the problem is to buy a more powerful uninterruptible power supply or turn off part of the equipment.

Won't turn on after power on

In the event that electricity has appeared in the network, but the UPS does not turn on, check the health of the battery, the connection to the network and the voltage level. The UPS will not be able to work for a long time if the mains voltage is low for a long time. In this case, the battery will be discharged and the device will stop turning on.

Sometimes, it is enough to connect the UPS to the network and just wait a while, the battery will charge and the device will start working. You should know how to check the UPS for the operability of its power button, it can be pushed through. Wire breaks are a common problem with uninterruptible power supplies. With a large overload, some brands of UPS refuse to work, it is enough to turn everything off and check it on by itself.

Turns off by itself, gets very hot

If there is voltage in the network, the uninterruptible power supply can turn off due to overload at the output

It is important to consider at what point the device turns off. If during a power outage, then most likely the problem is in the battery, you should check its performance

In the event that the device disconnects the load during operation from the network, it is quite possible that the software settings are to blame. The default settings should be checked and adjusted if necessary.

After opening the case, you can see obvious problems

The reason for the unstable operation of the device may be the use of non-branded accessories. In addition, it is likely that there will be other problems in the operation of the UPS.The bespereboynik can be disconnected from an overheat. In this case, you should check the health of the cooling system and make sure that there is no debris that prevents the free circulation of air, otherwise the device will turn off.

The UPS should be selected carefully, according to the voltage of the connected devices. When overloaded, the uninterruptible power supply will turn off, just as with insufficient load. Devices of some manufacturers determine the load below the installed power as the absence of working devices and turn off to save their own charge.

APC UPS Power Classification

The power of the uninterruptible power supply should meet the needs of the protected devices.

Distinguish:

• Low power uninterruptible power supply. They are made in desktop or floor versions and their range is 0.4-3 kW.
• An uninterruptible power supply of medium power is connected to a dedicated electrical network, placed both in special separate rooms and in rooms with the constant presence of personnel. Power range 3-40 kW. Often have a built-in power outlet. Execution floor or adapted for installation in a rack.
• A high power uninterruptible power supply requires a separate room and a dedicated electrical network. The power range is from tens to several hundreds of kW. Floor version.

You need to select an uninterruptible power supply with a power reserve of 20-30%, based on the needs of the equipment. It doesn't make sense to buy a powerful back UPS to protect your home computer. If the ups power is not enough, then it will disconnect from overload and all connected equipment will remain unprotected.

The apc uninterruptible power supply works well when you need to provide continuous power to office and home computers, as well as PBXs, telephones, faxes, switches and gateways. It has powerful overload and surge protection. This is true in places with unstable supply voltage in the network.

The UPS is an inexpensive and high-quality device.

Please note that the lack of an interface does not allow you to automate the shutdown of the computer in the event of a power failure. The excellent choice for work in power supply networks with a strong deviation of voltage from nominal.

UPS selection rules

UPSs are selected according to several parameters. It:

• Working hours;
• Load characteristics;
• According to manufacturers' recommendations;
• with special formulas.

Bezpereboynik should give the user time to correctly close the applications open on his computer. This time depends on the power of the consumed load, on the type of load. After all, the load can be not only a household computer, but also a server that stores very important data, or a gas boiler, the electronics of which must be protected, but not so critical according to requirements.

5.1. How to Calculate UPS Run Time

Each UPS has a label indicating the parameters of the device. A simple calculation is possible according to the power provided by the uninterruptible power supply and the power of the consumer. The load power (the simplest: you can see the power of the computer power supply on the label) should not be higher than the power declared by the manufacturer of the uninterruptible power supply. Then you are guaranteed to have time (approximately 15-20 minutes) to properly shut down the computer.

5.2. Factors affecting the running time

As already said this:

• Power consumption and nature of consumption;
• Battery capacity and their technical condition;
• UPS charger current.

The load may be different. Accordingly, losses are taken into account during the transfer of energy from the battery to the load. For this, various coefficients are used. For a computer, a factor of 0.85 is usually chosen.

Batteries have a capacity (measured in amp-hours) and a charge voltage. Over time, their capacity decreases. The rate of failure is affected by:

• Power consumption - there must be a power reserve;
• Conditions and frequency of switching on - the number of charge / discharge cycles is limited;
• Depth of discharge - it is impossible for the battery to be discharged to 0%;
• Battery operating temperature - at temperatures above 40 degrees, the battery discharges faster.

5.3. Manufacturer's recommendation

How to choose an IPB

A UPS manufacturer can predict battery life with great accuracy, as they thoroughly test their products before they go on sale. Therefore, you can always rely on his recommendations when choosing an uninterruptible power supply.

5.4. By formulas

To calculate the operating time, there is an average calculation of the battery life:

Battery Capacity (Amp-Hour) * Battery Voltage (Volts) / Continuous Load (Watts)

That is, if the battery capacity is 50 Amp-hours, the voltage is 12 V, the load power is -600 W, then 50 * 12/600 = 1 hour. This will be the offline load time.

There is an updated formula:

tibp \u003d Uakb * Sakb * N * K * Kgr * Kde / Rnagr

tibp - UPS battery life when the mains is turned off, h; Uacb - voltage of one battery, V; Sacb battery capacity, A * h; N - number of batteries in the battery; K - converter efficiency (h = 0.75-0, 8); Kgr - coefficient of discharge depth 0.8 -0.9 (80% -90%); Kde - coefficient of available capacity 0.7 - 1.0 (depending on the discharge mode and temperature); Rload - load power.

6. Additional features

In addition to the main function of the UPS - providing power to the equipment with electricity in case of power failures, all uninterruptible power supplies incorporate filters that limit impulse noise. More serious ones still regulate the input voltage. Double conversion uninterruptibles provide galvanic isolation of input and output, reliably protecting against any "energy cataclysms".

6.1. Synchronization with PC

The package includes a special program that allows you to connect the UPS to a computer and control the situation with the power supply. Connection is made via USB-, RS-232- or RJ-45 connector.

6.2. Cold start

This is the ability to turn on a computer with a UPS in the absence of external power and subsequent work. For example, urgent sending or receiving mail.

6.3. Socket

The output of the UPS can be equipped with several sockets of various types.

It:

• Ordinary euro socket (CEE 7/4);
• Computer (IEC 320 C13 or IEC 320 C19);

TYPES OF UNINTERRUPTIBLE POWER SUPPLY

The simplest UPS option is off-line power supplies, alternative name - "backup uninterruptible power supply unit". The principle of their operation is described in the previous section.They are the cheapest among the considered types of devices. The switching speed of the power circuits is in the range of 15-20 μs.

Scope of application - devices that are undemanding to the quality of the current, for which only work without stopping is necessary under any external conditions.

The disadvantages of this power supply: the lack of galvanic isolation and frequency stabilization. Autonomous mode is activated only at critical values ​​or power outage.

Line Interactive the power supply is more perfect, has a different principle of operation. An autotransformer is installed at the input of the device, the control system compares the value of the real voltage with the nominal one and brings it back to normal by switching the windings.

Thus, current and voltage surges are damped and filtered. The change in voltage is not linear, but stepwise. Response speed within 10 µs.

This block operates in the following modes:

• at a voltage close to the nominal: electrical network - autotransformer and battery charger - load;
• at emergency voltage values ​​and its absence: battery - inverter - load.

Disadvantages of linear-interactive sources: lack of frequency stabilization (in some cases this can be critical). In addition, there is also no galvanic isolation between the network source and the consumer.

Advantages: Thanks to stabilization, greater reliability and quality of consumer protection from poor-quality power supply is achieved. The price level is average.

The most complex and high-quality uninterruptible power supply is Online UPS, or double conversion UPS.

The principle of operation of this device is significantly different from the previous versions. The rectified voltage of the electrical network 220 V is supplied to the filter, then it feeds the charger and the inverter in parallel. The inverter provides load power, galvanic isolation from the mains, voltage shape and frequency correction.

Advantages of the Online block: constant maintenance of the nominal voltage and frequency at the output, the absence of bursts and interference, the presence of a pure sine wave. The response time when the input voltage is turned off is minimal.

The disadvantages include only the high price of the device.

Where does tension go and when will it return?

There are no networks that are 100% reliable. Suddenly, the lights in the apartment or house go out. This is due to damage to cable or overhead lines, electrical equipment of substations. Accidents within the city, if they are not related to natural disasters, are eliminated relatively quickly. For this, dispatch services and operational teams work. And it is possible to exclude the damaged section and replace it with another one because of their mutual redundancy.

In rural areas and summer cottages, everything is different. There is only one supply line, the brigade has to go far. After hurricanes or thunderstorms, the number of fallen trees on the wire lines increases the chances of staying in the dark for a long time. And if the power transformer is damaged, you will have to wait more than a day.

Overhead power line repair

Time goes by, the food in the refrigerator spoils. Do not boil the kettle - it is electric. Nothing to cook dinner. The battery of the mobile phone is discharged - it is impossible to call the Ministry of Emergency Situations. In the dark, you can't find a cure for grandma. The heating appliances cool down, and with them the house itself.

To prevent this from happening, you need a personal, network-independent source of power supply. For this purpose, an inverter is used.

UPS design

Linear UPSs are designed similarly to standby ones, but have a more complex design. The standard scheme of a standby UPS with a switching device is supplemented with a stabilizer that automatically regulates the voltage.

Consider the three main elements of the design.

switching device

This element of the design of the uninterruptible power supply provides switching between the operating modes between the external power supply and batteries. In line-interactive devices, the switching device is supplemented by a voltage regulator at the input.

Voltage regulator

One of the main elements of a line-interactive UPS. It can be both step-up with several steps, and universal (work both to increase and decrease the supplied voltage). The task of the stabilizer is to implement a circuit that is resistant to long-term voltage changes in the network. This allows solving the main problem inherent in the Russian power grids.

autotransformer

The UPS device does not provide galvanic isolation between input and output. Its functions are performed by input and output isolation transformers.

In most cases, battery packs act as power sources in offline mode. They are the most preferred due to reliability, cost and high resource. However, models with hydrogen-based fuel cells are also on the market.

Types of uninterruptible power supplies

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 - with hysteresis. That is, for example, when lowering, the transition to the battery will take place at 180 V or less, and vice versa - at 185 or more. The same principle applies to all types of UPS.

Smart UPS

Other names - Line-Interactive, interactive type UPS.

Smart UPS act smarter, as the name suggests. They also additionally switch the internal autotransformer, in a sense stabilizing the input voltage. And only in extreme cases go to the battery.

Thus, the norm of the output voltage is maintained with large deviations at the input (150 ... 300V). The autotransformer has several switching stages, so the Smart UPS switches the autotransformer outputs to the last, including the battery only at the last moment. This allows you to save the battery, turning it on only when the power is completely lost.

Online UPS

Other names are 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 a constant voltage, and fed to the inverter, which generates a pure sine wave. And at the same time - maintains the battery in 100% readiness. If necessary, the inverter continues to work in the same way, only the power is supplied to it 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

Uninterrupted power supply for DC consumers

For some devices, it is necessary to provide uninterrupted power supply with direct current 12, 24 or 48 V. A UPS of this kind is also on sale. Their labeling contains the abbreviation “DC”. Blocks with a voltage supply of 60, 110 or 220 V also exist, but they are used in industry or energy.

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

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

Together with voltage converters, a 48W DC UPS is capable of powering a video surveillance system with a perimeter of up to 1 km

These standby power supplies are used to protect the following DC household equipment:

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

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

HOME UNINTERRUPTIBLE POWER SUPPLY

When purchasing a device, you should determine the power of the consumer that is planned to be connected to the UPS, as well as the battery life. As an example, we can consider several typical situations.

If you need to ensure the ability to safely shut down your computer without losing important data, and you do not need long-term operation in the absence of mains power, then a standby off-line UPS will be the ideal solution.

Budget models will provide the computer with electricity for 5-15 minutes of battery life. This is enough to save the results of the work and turn off the computer. For an average computer, power from 250 W to 1 kW is enough.

If an autonomous heating system is used using a modern gas boiler, then an unstable power supply can damage the control boards.

To ensure the normal operation of such boilers, a pure sine wave is needed, so you will have to purchase an appropriate line-interactive or online UPS, despite its high cost.

If the apartment is equipped with an alarm system, then power outages can pose a serious property threat, so any fire alarm system includes a UPS. For the simplest signaling systems, a backup or line-interactive power supply unit with a long battery life is sufficient.

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Main characteristics

An important characteristic of a UPS is its output power.The total power of devices that can be connected to this source depends on it. To determine it, you need:

• check the power of each device that will work through the UPS, and add everything up;
• we translate the value obtained in the previous step from watts to VA, for this we divide it by the power factor (cosϕ) equal to 0.6;
• to ensure a margin, we increase the resulting value by 20%, that is, we multiply everything by 1.2.

Let's give an example of a calculation. Let's say we have a 250W computer, a 30W monitor, and 5W speakers.

We determine their total power:

Pw = 250 + 30 + 5 = 285 W.

Now you can find out the minimum allowable power of the UPS:

Pva = (Pw / 0.6) * 1.2 = (285 / 0.6) * 1.2 = 570 VA

When determining the power consumed by a personal computer, it is wrong to focus on the power of its power supply. You can determine the real value using a household ammeter or wattmeter with a socket. If there is no such device, then you can calculate the required value using an apartment meter. For this you need:

• disconnect from the network all devices that consume electricity;
• turn on the PC and run a frequently used program on it;
• when the meter readings increase by one tenth of a kilowatt, start counting the time until the next change in readings;
• calculate the power consumed by the computer using the formula: P \u003d 100 * (60 / t), where t is the time the meter reading changes by 0.1 kW.

The next most important parameter will be the time during which the UPS will be able to ensure the functioning of the devices connected to it during a power outage. Often manufacturers indicate the value that is measured when connecting the maximum load

But usually the uninterruptible power supply operates at capacities less than the maximum, and its battery life will be longer than that declared by the manufacturer. The increase in the duration of work is not proportional to the decrease in the magnitude of the load. With a decrease in the total load power by half, the battery life can increase by 2.5–5 times, and with a triple load drop, by 4–9 times.

When choosing an uninterruptible power supply, you should also pay attention to the characteristics:

• device output voltage;
• transfer time is the time it takes for the UPS to transfer from utility power to battery operation.

Before buying a UPS, you need to determine what equipment you will connect to it - it depends on how many and what connectors will be at the output of the power source. Often there are such interfaces:

CEE 7 Schuko, or euro socket, is needed to connect a Wi-Fi router or other equipment;

IEC 320 C13, or computer connectors.

The display itself can also be useful. It can display important information: the voltage at the input and output of the device, the battery charge level, the output power.

Uninterruptible power supplies built on the principle of double conversion, as well as some line-interactive models, generate a lot of heat during operation and need to be removed. Most often, a fan is used for this purpose, which makes noise.

At this point it is also worth paying attention

These are all the main characteristics of the UPS.

Types of uninterruptible power supplies

Uninterruptible switches are classified into three types depending on the design schemes:

1. The standby is used to switch to battery power.
2. Interactive is used for line-interactive uninterruptible power supplies.
3. The double conversion circuit is designed for online power supplies.

Backup sources

An offline UPS or a backup source is needed for home computers and maintaining local networks in offices.

The principle of operation is the automatic switching of the PC to battery power in the event of a power outage. The role of the switch is played by a mechanical relay, which makes the UPS make clicking sounds when changing operating modes.

Linear operational

Such UPSs are used to protect network and telecommunications equipment or a group of computers against voltage drops.

A feature of the work is the protection of the PC from overvoltage or undervoltage without switching to emergency mode due to the inclusion of an autotransformer in the circuit.

Power supplies online (for servers)

Powerful double conversion UPS is used for file servers, server workstations and network devices that are demanding on the supply voltage.

Features of the action - input alternating voltage is converted rectifier to DC, then through the inverter to the reference variable, which is fed to the devices. The storage battery is permanently connected to the rectifier output and the inverter input and constantly feeds them in emergency mode.

UPS online provide stable voltage to servers and zero transfer time to batteries.