The unit called "three-phase voltage stabilizer" is a complex electronic device that allows you to maintain the output power parameters at the desired level. The need for these products is caused by the instability of the 380 volt mains supply, the fluctuations of which sometimes reach dangerous values. When installing stabilizers, it is possible to save industrial and household equipment connected to it, which often fails due to voltage exceeding limit values.
Design features
By its design, a three-phase stabilizer is three single-phase modules of the same type with a common control and monitoring circuit. There are two known versions of such devices:
- In the first case, it is a single design that includes three independent stabilization circuits.
- The second option represents three identical single-phase stabilizers connected in a "star" scheme and placed in the form of modules in a single rack.
The first of the versions is used for servicing low-power consumers and is relatively cheap. But for this you have to pay with serious problems that are possible during its operation. If one of the 3 schemes fails, the entire structure has to be repaired or completely renewed. The second modification (in the form of a rack with independent modules) is distinguished by increased functionality, which allows not to interrupt the power supply in the event of a failure of one of the phase lines. In this case, the voltage is applied to the output directly, bypassing the problem module.
A feature of connecting any modifications is the separate supply of the phase to each of the converters, while the working zero remains common to them. In addition, the housings of these devices must be connected to an existing grounding circuit at an industrial facility.
The control and monitoring circuit of 380 V voltage stabilizers operates according to a special algorithm that allows not only adjusting the output voltage value, but also turning off the device in the following emergency cases:
- the voltage value of one of the phases is below or above the critical level;
- the temperature of the control elements of the converter modules exceeds the preset threshold;
- a strong phase imbalance was found in the consumption circuit.
Phase imbalance is typical for the operating mode with an uneven load, when the values of the phase voltages are shifted towards zero of the transformer neutral.
A 4-pole circuit breaker built into the unit is used as a protective element that disconnects the load in an emergency. The 3-phase stabilizer is externally designed as a vertically installed floor structure. On its front panel, in addition to controls, voltage indicators are displayed, made in the form of dial voltmeters or modern digital indicators.
Principle of operation and scope
- the basis of most stabilizers is a converter-transformer with an adjustable number of turns at the output, which makes it possible to change the voltage across them in one direction or another;
- as long as the readings at the input correspond to the nominal, normal 220 volts are removed from the output winding;
- if the input voltage has changed up or down, the controller built into the stabilizer processes the difference and sends a control signal to a special motor mechanism;
- the latter moves the voltage puller slider in the desired direction, adjusting the output voltage until it reaches its nominal value.
Among the samples of stabilizing devices produced by the industry, there are models with smooth and stepwise control.
The field of application of three-phase stabilizers is quite wide. They are installed in power supply circuits not only in production, but also at home, mainly in private and country houses. Stabilizing devices for household needs, as a rule, have a low power rating, limited to 30-50 kW. More energy-intensive units (up to 100 kW) are often installed in city offices, in suburban settlements, as well as in small enterprises.
For a personal dacha, a device that guarantees output power up to 50-70 kW is quite enough. Industrial samples of stabilizers with a declared power of more than 100 kW are installed in the shops of factories, in medical institutions, as well as at exhibition sites and in shopping centers. Devices with galvanic voltage isolation, operating in high humidity conditions, are in demand in specialized medical institutions, laboratories and scientific centers.
Types of three-phase stabilizers
The industry has launched the production of a large number of modifications of stabilizers designed to operate in three-phase networks. A list of the main types of such units:
- relay and thyristor devices;
- electromechanical stabilizers;
- ferroresonant and inverter models;
- hybrid appliances.
Each of these positions needs separate consideration.
Relay and thyristor samples
In relay devices, electromagnetic relays are used to switch the turns of the output coil of the built-in transformer. Systems of this class are characterized by sufficient speed and are convenient in operation and maintenance. However, due to the mechanical nature of the switching, they are not durable enough (the relay actuation resource is limited). At the same time, the accuracy of adjusting the output indicators of relay units is insufficient for practical needs.
Thyristor devices do not contain mechanical contacts, since their switching circuit is built on the basis of semiconductor devices. Due to this, the indicators of reliability and durability of the stabilizer increase sharply, and the resource is practically unlimited. Thanks to the well-functioning production of modern electronic components, the cost of such a device is low.
Electromechanical models
In units of this type, the output voltage is adjusted by mechanically moving the brushes of the current collector, which is part of the built-in servo drive. This explains the low rate of regulation of the output parameter, which does not exceed 15 Volts per second. Other disadvantages of these devices include:
- excessive noise;
- strong sparking during work;
- low inertia (the device does not have time to respond to sudden changes in the input voltage).
A positive quality of electromechanical devices is the high accuracy of setting the output indicators (voltage and power).
Ferroresonant stabilizers
This type of stabilizing devices resembles conventional transformer models, in which the magnetic circuit has a pronounced asymmetry. This is how it differs from typical designs with nonlinear magnetic characteristics. A significant drawback of these units is their low power efficiency.In addition, when it is necessary to control large current loads, the line choke is obtained of significant dimensions.
To reduce the size and weight of the device, a capacitor is introduced into it, due to which the magnetic circuit acquires resonant properties. Hence the name of this unit - ferroresonant regulator. Today, this type of stabilizer (like its electromechanical counterpart) is used only in special cases. In everyday life, they were replaced by modern electronic devices called inverters.
Inverters
Inverter models are built according to a complex electronic circuit that includes several steps for converting the input voltage. Thanks to this, it is possible to obtain an almost ideal regulator that allows you to maintain the output level with an accuracy unattainable for other stabilizers. The range of permissible input oscillations has also been expanded, and the control speed is limited only by the speed of the output key elements (high-frequency transistors). The only drawback of electronic units is their high cost.
Hybrid devices
This type of stabilizing device appeared on the market relatively recently (in 2012). The basis of its design is a mechanical regulator, which includes two relay-type converters. In normal mode, only an electromechanical device works, and additional units come into operation when the main module can no longer cope with its functions.
The inability to maintain the optimal level at the output usually manifests itself when the input voltages are too low or too high, limited to the range from 144 to 256 volts. If this value is less than 144 or higher than 256 volts, the second stage of stabilization, assembled on an e / m relay, starts to work. The maximum adjustment range is from 105 to 280 volts.
