The operating principle of an uninterruptible power supply. How do uninterruptible power supplies (UPS) work?

A friend of mine at the company threw away a non-working uninterruptible power supply of the APC 500 model. But before using it for spare parts, I decided to try to revive it. And as it turned out, it was not in vain. First of all, we measure the voltage on the rechargeable gel battery. For the uninterruptible power supply to function, it must be within 10-14V. The voltage is normal, so there is no problem with the battery.

Now let's inspect the board itself and measure the power at key points in the circuit. I couldn’t find a native circuit diagram for the APC500 uninterruptible power supply, but here’s something similar. For better clarity, download the full version here. We check the powerful left-field transistors - the norm. Power to the electronic control part of the uninterruptible power supply is supplied from a small 15V mains transformer. We measure this voltage before the diode bridge, after, and after the 9V stabilizer.

And here is the first swallow. The 16V voltage after the filter enters the stabilizer chip, and the output is only a couple of volts. We replace it with a model of similar voltage and restore power to the control unit circuit.

The uninterruptible power supply began to crackle and buzz, but there was still no sign of 220V output. We continue to carefully inspect the printed circuit board.

Another problem - one of the thin tracks burned out and had to be replaced with a thin wire. Now the APC500 uninterruptible power supply device is working without problems.

Testing it in real conditions, I came to the conclusion that the built-in buzzer signaling the absence of a network is screaming like crazy, and it wouldn’t hurt to calm it down a little. You can’t turn it off completely - since you won’t be able to hear the state of the battery in emergency mode (determined by the frequency of the signals), but you can and should make it quieter.

This is achieved by connecting a 500-800 Ohm resistor in series with the sound emitter. And finally, some advice to owners of uninterruptible power supply systems. If it sometimes turns off the load, there may be a problem with “dried up” capacitors. Connect the UPS to the input of a known good computer and see if the alarms stop.

The uninterruptible power supply sometimes incorrectly determines the capacity of lead batteries showing the status OK, but as soon as it switches to them, they suddenly run out and the load is “knocked out”. Make sure the terminals fit snugly and are not loose. Do not disconnect it from the network for a long time, making it impossible to keep the batteries constantly charged. Avoid deep discharges of batteries, leaving at least 10% capacity, after which you should turn off the uninterruptible power supply until the supply voltage is restored. At least once every three months, do a “training session”, discharging the battery to 10% and again charging the battery to full capacity.

Discuss the article REPAIR OF A UPS

Uninterruptible power supply. Device characteristics: direct conversion from direct 12 volt voltage to alternating voltage 220 V with a frequency of 50 Hz (). Maximum power - 220 W. Reverse conversion - used to charge the battery. Charging current about 6 A. Fast switching from direct conversion to reverse mode.

The uninterruptible power supply diagram is shown below

A clock generator is assembled on elements VT3, VT4, R3...R6, C5, C6, which generates pulses with an average frequency of 50 Hz. The generator controls the operation of transistors VT1, VT6. Windings IIa, IIb of transformer T1 are connected to the collector circuit of these transistors.

Diodes VD2, VD3 are used as a rectifier in reverse mode and to protect transistors VT1, VT6 in forward mode. The network filter is made on elements C1, C2, L1, and on elements VD1, SZ, C4 the clock generator filter.

Operation of uninterruptible power supply:

Direct conversion: +12 V voltage is alternately applied to windings IIa or IIb, and transformer T1 converts it to 220 V/50 Hz. This voltage is present at the XS1 socket, and all kinds of consumers are connected to it (incandescent lamps, TV, etc.)

The indicator of normal operation is the lighting of LEDs VD4, VD5. The load current can reach 1 A, which corresponds to a power of 220 W.

Details and design

T1 - you can use any transformer that provides two output voltages of 10V with a load current of up to 10 A. Coil L1 is made on a K28x16x9 M2000NM ferrite ring. The ring should be pre-wrapped with varnished cloth, and then two windings of 10 turns of wire with a diameter of 0.55...0.70 mm should be wound. Transistors VT1, VT6 and diodes VD2, VD3 should be installed on a radiator with an area of ​​at least 200 cm2. through mica plates.

Attention! Since the circuit elements are under mains voltage, electrical safety measures should be observed when setting up the device.

The low-power switching power supply can be used in a wide variety of amateur radio designs. The circuit of such a UPS is particularly simple, so it can be repeated even by novice radio amateurs.

Main parameters of the power supply:
Input voltage - 110-260V 50Hz
Power - 15 Watt
Output voltage - 12V
Output current - no more than 0.7A
Operating frequency 15-20kHz

The initial components of the circuit can be obtained from available trash. The multivibrator used transistors of the MJE13003 series, but if desired, they can be replaced with 13007/13009 or similar. Such transistors are easy to find in switching power supplies (in my case, they were removed from a computer power supply).

The power supply capacitor is selected with a voltage of 400 Volts (in extreme cases, 250, which I strongly do not recommend)
The zener diode used was a domestic type D816G or an imported one with a power of about 1 watt.

Diode bridge - KTs402B, you can use any diodes with a current of 1 Ampere. Diodes must be selected with a reverse voltage of at least 400 volts. From the imported interior you can install 1N4007 (a complete domestic analogue of KD258D) and others.

The pulse transformer is a 2000NM ferrite ring, the dimensions in my case are K20x10x8, but large rings were also used, but I didn’t change the winding data, it worked fine. The primary winding (network) consists of 220 turns with a tap from the middle, the wire is 0.25-0.45 mm (no more sense).

The secondary winding in my case contains 35 turns, which provides an output of about 12 Volts. The wire for the secondary winding is selected with a diameter of 0.5-1mm. The maximum power of the converter in my case is no more than 10-15 watts, but the power can be changed by selecting the capacitance of capacitor C3 (in this case, the winding data of the pulse transformer is already changing). The output current of such a converter is about 0.7A.
Select a smoothing capacitance (C1) with a voltage of 63-100 Volts.

At the output of the transformer, you should use only pulse diodes, since the frequency is quite high, conventional rectifiers may not cope. FR107/207 are perhaps the most affordable of the switching diodes, often found in network UPSs.

The power supply does not have any short circuit protection, so you should not short-circuit the secondary winding of the transformer.

I didn’t notice any overheating of the transistors; with an output load of 3 Watts (LED assembly), they are icy, but just in case, they can be installed on small heat sinks.

List of radioelements

Domestic electricity supply is characterized by low reliability and unsatisfactory This is due to outdated electrical networks, wear and tear of equipment, low performance of energy converters, transient processes at sources and users of electricity, natural and climatic factors. In such conditions, uninterruptible power supply systems are extremely necessary to ensure the operation of consumers of both the first and other categories.

For apartment and house owners, stable operation of the electrical network is also important. Stopping the operation of household appliances is not the worst of the troubles. Much more important is the trouble-free functioning of life support systems, in particular the heating system, if it directly depends on the power supply. Uninterruptible power supply UPS (UPS) comes to the rescue - a device that protects electrical receivers from shutdowns by storing electricity in rechargeable batteries (AB) and guarantees the required quality of energy (QE) in autonomous and network operating modes.

Before outlining an approach to creating power supply to loads without failures, you should find out what failures can be expected from domestic power grids.

Power failures in electrical networks

Low voltage is a common occurrence in the power supply. But it is not particularly dominant over the elevated one, which is also common. At night, the voltage is stable, during the day it decreases, and in the evening, when most of the loads are turned off, it increases.

Unstable frequency is also a failure, although quite rare. When the network is heavily loaded, it can drop to 45 Hz, which leads to significant signal distortion that negatively affects the operation of the UPS. Some devices perceive a decrease in frequency as an emergency, and the battery can quickly drain.

A complete power outage is not such a rare occurrence. Electricians are not very careful with the operation of electronics and can unexpectedly cut off power to a building. A momentary power outage is enough to cause loss of information on a computer. When networks are overloaded, power outages can occur. Therefore, it is important how reliably the UPS system supplies uninterruptible power.

UPS classification

They are divided into three groups:

1. Low-power UPS for connection through electrical outlets. The design can be desktop or floor-standing, and the power ranges from 0.25 to 3 kW.
2. Medium power devices - from 3 to 30 kW - contain a block of sockets built inside, or are also connected through groups of sockets in the consumer power supply network from the control panel. The devices are manufactured for placement both in offices and in separate equipped rooms.
3. High power UPS - from 10 to 800 kW. Located in electrical machine rooms. They are collected in groups and created high-power energy systems - up to several thousand kW.

UPS types

There are currently 4 types of UPS (UPS). The properties common to all are:

• filtering from impulses and noise;
• elimination of signal shape distortions;
• voltage stabilization (not available for all models);
• keeping the battery charged;
• When the UPS battery is low, it will first signal and then shut down the consumer.

Off-line UPS

The principle of operation of devices of this modification is to power the consumer from the existing network and instantly switch to an autonomous backup power supply in emergency situations (4-12 ms). They are simpler and cheaper than other types.

The UPS usually switches to operation from the built-in battery.

When operating from the mains, the device suppresses noise with pulses and maintains the voltage at a given level. Part of the energy is spent on recharging the battery. If the network operates in a non-standard mode, the consumer switches to battery operation. Each UPS model determines in its own way the need to switch to this mode. The operating time of the battery depends on its characteristics and the power consumed by the load. If the backup power supply is discharged, a command is given to turn off the consumer. If the mains voltage reaches a normal level, the UPS switches to normal mains operation mode and battery charging begins.

Linear interactive

Line interactive ups models are equipped with stabilizers that operate continuously and ensure that batteries are rarely connected.

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

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

Ferroresonant UPS

The device contains a ferroresonant transformer, which works as a voltage stabilizer. Its advantage is the accumulation of energy in the magnetic field, which is released during switching within 8-16 ms. This period of time is enough for the UPS to enter a new operating mode.

The transformer performs the additional function of a noise filter. Input voltage distortion does not affect the output waveform, which remains sinusoidal.

Double Conversion UPS

The double energy conversion device works on the principle of rectifying the mains voltage, and then again converting it into stabilized alternating voltage. Here a more powerful rectifier is used, which not only recharges the battery, but also supplies the inverter with a stabilized constant voltage.

From the output of the device, a stabilized alternating voltage is supplied to the load.

When double conversion is not enough to adjust the grid voltage, additional charge is supplied from the battery to the inverter. There are no switches, but the mode is already different.

If the inverter fails, it switches to operation from the mains via a bypass. Choosing a double conversion UPS for private use is irrational due to high energy losses. This type of protection is used by organizations that require high equipment reliability.

Types of systems

Uninterruptible power supply systems can be centralized or distributed. In the first case, one UPS operates for the entire building or a separate floor, which copes with all loads.

Uninterruptible power supplies include several protection devices, each of which operates on a single computer or other piece of equipment. They are quite effective.

The advantages of a distributed system are as follows:

1. The UPS is selected specifically for an individual device that is the most critical or operates in harsh conditions.
2. The system can be gradually expanded, starting with server protection and moving to workstations.
3. Failed UPSs can be replaced with others from less important system elements.
4. The low-power UPS does not require installation and maintenance by special personnel.
5. Possibility of connecting to a regular power supply via sockets.
6. UPSs are used independently of each other.

Centralized uninterruptible power systems include high-level UPSs that better protect equipment. Despite their high cost, overall cost savings are achieved since one device is cheaper than several. But for simple computers, the system will cost more, since its maintenance requires highly qualified personnel or the services of specialized companies that install uninterruptible power supply systems and service them.

It is necessary in the following cases:

• computers are the main load on the network;
• some organizations need very reliable systems, such as banks;
• consumers vary significantly in power: computer system, communications, security system.

What to look for when choosing a UPS?

When choosing an uninterruptible power supply system, there are several important factors to consider. Let's list the main ones.

What is the equipment protected from?

First of all, it is necessary to measure the voltage in the electrical network. The minimum cycle duration will be a day. It best reflects the operation of the electrical network. If you have to work on weekends, you need to get information on a weekly cycle, during the day and night.

It is important to determine the maximum and minimum voltage, as well as the power and frequency of pulses in the network. The device can be a recorder.

The simplest way for the user is to measure the voltage, during which, in his opinion, the voltage reaches a maximum and minimum. Don't ignore weekends.

If the apartment owner has powerful equipment, it is necessary to measure the voltage in the home network when it is turned on and off. You should find out how often the power supply at home is cut off and for what reasons. It is important to have a grounding wire in the apartment. In this case, you should find out how reliably it is connected to the floor panel bus.

Type of protected equipment

A list of equipment that requires the use of a UPS is compiled. In this case, you need to know what is consumed by each. It is enough to determine its nominal value, which is in the technical specifications. Some equipment sometimes consumes maximum energy that is several times its rated value. A power reserve should be set for it.

Battery life

Here it is important to determine for what period it is possible to safely save data or complete the necessary technological operations (transferring information, saving files, receiving messages).

Required Personnel

Depending on the complexity of the system, a certain staff of specialists is required to operate it. This must be clarified in order to correctly calculate all costs. The price of the protection system should not exceed 10% of the cost of the main equipment.

UPS for home

For an average cottage, a UPS (UPS) uninterruptible power supply system with a power of about 15 kW is convenient. To ensure autonomous operation for 2-3 hours, you need 4 batteries with a total capacity of 2000 Ah. They allow you to accumulate electricity of about 7 kWh.

In the house, the most important ones are the heating system and household appliances with a computer. The cost of a UPS depends on the power, number of batteries and manufacturer. For a boiler, you can purchase a source with a power of 360 W at a price of 7 thousand. For the whole house you will need a UPS power of up to 15 kW, the price of which is more than 70 thousand rubles.

In addition to the converters, batteries are needed, which need to be changed periodically. A UPS for a home costs a lot of money. Battery uninterruptible power supply systems are especially expensive.

Despite this, you can save on repairing other equipment. In addition, there are alternative options using generators. Sometimes you can get by with installing voltage stabilizers, which cope with many tasks, including correctly turning off equipment.

Modern UPSs are equipped with a clear interface. Using the display, you can monitor the operation of the system, where the main parameters are input and output voltage, power consumption, operating circuit, battery charge.

Which UPS to choose depends on the user's needs. A home computer may have enough power for the duration of its shutdown. For uninterrupted operation of the boiler for 8-9 hours, you will need a 1 kW protective device with three 65 A/h batteries.

Conclusion

The systems are designed to ensure autonomous operation of electrical appliances and electronic equipment for a short time. The main indicator is the power of the UPS and the capacity of the battery. It is advisable to choose equipment that contains a voltage stabilizer.

The operating time of the battery depends on its characteristics and the power consumed by the load. If the backup power supply is discharged, a command is given to turn off the consumer. If the mains voltage reaches a normal level, the UPS switches to normal mains operation mode and the battery begins charging.

How to make an uninterruptible power supply yourself? Pure sinusoidal output voltage, suitable for powering any devices. (10+)

How to make a UPS with a sinusoidal output yourself

Is it worth assembling the UPS yourself?

Does it make sense to assemble the UPS yourself? Don't know. There are kilowatt uninterruptible power supplies on sale for 30 thousand rubles. These products are definitely of higher quality, reliability and energy efficiency than homemade ones. The cost of a homemade one, if assembled from ready-made blocks, is around 20 thousand rubles. I collected it when there was nothing like it on sale. In any case, I’m sharing my experience. My UPS has been working great for 8 years now. Please note that this is a permanent device. It does not turn off when there is voltage in the network, but works constantly. So he actually worked continuously for eight years. Changing the circuit so that it turns off and on automatically if you need it will not be difficult for a specialist who can assemble it. I use a continuously operating device because I have several energy-critical consumers in my house: computers, a server, a smart home system. When switching from mains to battery power, a voltage surge occurs that is unacceptable.

You can assemble the entire uninterruptible power supply yourself, then the cost of parts for it will be 10 thousand rubles.