Domestic power supply is characterized by low reliability and unsatisfactory quality of electricity. This is due to outdated electrical networks, depreciation of equipment, low characteristics of energy converters, transient processes at sources and users of electricity, natural and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 work of consumers of both the first and other categories.
For owners of apartments and houses, stable operation of the power grid is also important. The cessation of household appliances is not the biggest of 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 power consumers from shutdown due to the accumulation of electricity in rechargeable batteries (Batteries) and guarantees the necessary quality of energy (CE) in stand-alone and network operation.
Before outlining an approach to creating power supply for loads without failures, you should find out what failures can be expected from domestic power grids.
Power Failures
Undervoltage is a common occurrence in power supply. But it does not particularly prevail over elevated, which is also often found. 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.
An unstable frequency is also a malfunction, although quite rare. With a high network load, it can drop to 45 Hz, which leads to significant signal distortions that negatively affect the operation of the UPS. Some devices perceive a decrease in frequency as an accident, and the battery can drain quickly.
A complete blackout is not such a rare case. Electricians do not really reckon with the work of electronics and can suddenly turn off the building. A momentary power outage is enough to lose information on a computer. When networks are overloaded, power outages can occur. Therefore, it is important how the UPS system reliably delivers uninterrupted power.
UPS classification
They are combined into three groups:
- Low-power UPS for connection via electrical outlets. Execution can be desktop or floor, and the power ranges from 0.25 to 3 kW.
- Medium-power devices - from 3 to 30 kW - contain a block of outlets that are built in, or are also turned on through groups of outlets in the consumer power network from the control panel. Devices are made for placement both in offices and in separate equipped rooms.
- High power UPS - from 10 to 800 kW. They are located in electrical rooms. They are assembled into groups and create high-power energy systems - up to several thousand kW.
UPS types
Now 4 types of UPS (UPS) are common. Common to all properties are:
- filtering from impulses and noise;
- elimination of distortion of the waveform;
- voltage stabilization (not on all models);
- keeping the battery charged;
- when the UPS battery is discharged, it first gives a signal and then turns off the consumer.
Off-line UPS
The principle of operation of devices of this modification is to power the consumer from an existing network and instantly switch to stand-alone backup power in emergency situations (4-12 ms). They are simpler and cheaper than other types.
The UPS usually switches to on-board operation.
When operating from the network, the device suppresses noise with pulses and maintains voltage at a given level. Part of the energy spent on recharging the battery. If the network operates in non-standard mode, the consumer switches to battery operation. Each UPS model in its own way determines the need to switch to this mode. Operating time through the battery depends on its characteristics and power consumption. In case of discharge of the backup power source, a command is issued to turn off the consumer. If the mains voltage reaches a normal level, the UPS goes into normal mains operation mode, and battery charging starts.
Line Interactive
Line interactive ups models are equipped with stabilizers that operate continuously and provide a rare battery connection.
The device interacts with the network, 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 tolerance and the switching range is no longer enough, the UPS switches to battery backup. The unit can be disconnected from the main power when a distorted waveform arrives. There are models that correct the shape of the voltage without switching to battery operation.
Ferroresonant UPS
The device contains a ferroresonant transformer that acts as a voltage stabilizer. Its advantage is the accumulation of energy in a 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 an additional function of the noise filter. Distortion of the input voltage does not affect the shape of the output, which remains sinusoidal.
Double Conversion UPS
The double energy conversion device works on the principle of rectifying the voltage of the network, and then again turns it into a variable stabilized one. A more powerful rectifier is used here, which not only recharges the battery, but also supplies the inverter with a constant constant voltage.
From the output of the device, an alternating stabilized voltage is supplied to the load.
When double conversion is not enough to adjust the mains voltage, an additional charge comes from the battery to the inverter. Switching does not occur, but the mode is already different.
When the inverter fails, it switches to mains operation via bypass. Choosing a double conversion UPS for private use is irrational due to large energy losses. This type of protection is used by organizations where high reliability of equipment is required.
Types of systems
Uninterruptible power systems can be centralized or distributed. In the first case, one UPS operates on the entire building or a separate floor, which copes with all the loads.
Distributed uninterruptible power systems include several protection devices, each of which works on one computer or another piece of equipment. They are quite effective.
The benefits of a distributed system are as follows:
- The UPS is selected specifically for the individual device, which is the most important or operating in harsh conditions.
- The system can gradually grow, starting with server protection and moving to workstations.
- Failed UPSs can be replaced with others with less important system elements.
- A low-power UPS does not require installation and maintenance by specialized personnel.
- The ability to connect to a conventional electrical outlet through outlets.
- 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, because its maintenance requires highly qualified personnel or the services of specialized firms that install uninterruptible power systems and their maintenance.
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, emergency lighting, communication, security system.
What to look for when choosing a UPS?
When choosing an uninterruptible power supply system, several important factors must be considered. We 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 in duration will be a day. It most closely reflects the operation of the electrical network. If you have to work on weekends, you need to get information on the 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 the pulses in the network. The device can be a digital oscilloscope or recorder.
The easiest way for the user is to measure the voltage, during which, in his opinion, the voltage reaches a maximum and a minimum. Do not disregard the weekend.
If the owner of the apartment has powerful equipment, you need to measure the voltage in the home network when it is turned on and off. You should find out how often the voltage in the house is turned off and for what reasons. It is important that the apartment has a ground wire. In this case, you should find out how reliably it is connected to the bus of the floor board.
Type of protected equipment
A list of equipment is compiled for which the use of a UPS is necessary. In this case, you need to know the power consumed by each device. It is enough to determine its nominal value, which is in the technical specifications. Some equipment sometimes consumes maximum energy, several times higher than the nominal value. For it should establish a margin of power.
Battery life
It is important to determine for what period you can safely save data or complete the necessary technological operations (transfer of information, saving files, receiving messages).
Staff needed
Depending on the complexity of the system, a certain staff of specialists is required for its operation. It is necessary to find out in order to correctly calculate all the 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, an uninterruptible power supply system UPS (UPS) with a capacity of about 15 kW is convenient. To ensure battery life for 2-3 hours, you need 4 batteries with a total capacity of 2000 Ah. They allow you to accumulate electricity about 7 kWh.
In the house, the most important are the heating system and household appliances with a computer. The cost of the UPS depends on the power, the number of batteries and the manufacturer. For the boiler, you can purchase a source with a power of 360 W at a price of 7 thousand. For the whole house you need UPS power up to 15 kW, the price of which is more than 70 thousand rubles.
In addition to converters, batteries are needed that need to be changed periodically. UPS for the house costs a round sum. Particularly costly are uninterruptible power systems.
Despite this, you can save on repairing the rest of the equipment. In addition, there are alternatives using generators. Sometimes you can do with the installation of voltage stabilizers that cope with many tasks, including the correct shutdown of equipment.
Modern UPSs have an intuitive interface. The display can monitor the operation of the system, where the main parameters are the voltage at the input and output, power consumption, operation scheme, battery charge.
Which UPS to choose depends on the needs of the user. There may be enough power for a home computer to shut it down. For uninterrupted operation of the boiler for 8-9 hours, a protective device for 1 kW with three batteries of 65 A / h is required.
Conclusion
Uninterruptible power systems are designed to provide autonomous operation of electrical appliances and electronic equipment for a short time. The main indicator is UPS power and battery capacity. It is advisable to choose equipment containing a voltage stabilizer.
Operating time through the battery depends on its characteristics and power consumption. In case of discharge of the backup power source, a command is issued to turn off the consumer. If the mains voltage reaches a normal level, the UPS switches to normal mains operation and battery charging begins.