The current voltage of 220 volts in the electric network in the form in which it enters the apartment is unsuitable for the operation of most electronic devices. To convert it to a convenient type for powering household appliances, special converters called transformers are required. With their help, it is possible to lower the value of the supply voltage to the desired value, and then straighten it.
Transformer Overview
As converters, these devices are traditionally used to bring to an acceptable form of power sent over high-voltage lines. For "transfer" to vast distances, only ultra-high voltages are suitable at which the current can have an acceptable value.
If you try to transfer energy at least a hundred kilometers in the form of the usual voltage of 380 volts, a current of millions of amperes will be required to deliver the required power to the consumer.
For its dispersion, a wire is needed about the thickness of a human body, which in practice is impossible to implement. Therefore, on the side of the electricity-generating side, with the help of another (step-up) transformer, its value rises to 110 kV. In this form, it is impossible to use electricity distribution in residential buildings and production facilities. Therefore, after delivery via explosives in distribution stations, 110 kV are reduced to 10 (6) kV.
From here they go to the district transformer substations, where in the local step-down transformer they get their final form 380 (220) Volts. With such potential values, energy can easily be transported through an underground cable or an SIP aerial wire to the final consumer. Therefore, a single-phase transformer plays a large role in human life.
Purpose and device
Any 220 Volt single-phase transformer is an electrical device that works only in AC circuits. With its help, the input voltage is converted to the desired value (most often it decreases). In this case, the current drawn from the secondary winding increases, since the power is transmitted almost without loss. It follows that the main purpose of this device is to obtain the voltage necessary for solving problems, and then use it for specific purposes.
Familiarity with the design of the transformer, which consists of the following main elements, will help to make a more complete picture:
- core made of ferromagnetic materials;
- primary and secondary coils placed on an insulated frame;
- protective cover (this element is absent in a number of models).
In some samples, instead of ferromagnets, electrical steel or permalloy is used. The choice of a particular type of core material depends on the area of use of the product itself.
Operating principle
The principle of operation of a single-phase transformer is based on the law, according to which the alternating electric field acting in the coil induces an EMF in a conductor located nearby. The phenomenon is called the law of electromagnetic induction of Faraday, who was the first to discover this interesting effect. To substantiate it, the scientist developed a whole theory, which formed the basis of the work of most modern electrical devices and assemblies.
Its main provisions:
- when a current passes through a coil of wire, a magnetic flux is formed around it, capturing all the same turns located nearby;
- under the influence of this flow, an EMF is induced in them, coinciding in the form of changes with the initial field;
- in the presence of a ferromagnet in it, the effect of this effect is enhanced.
All these principles are the basis for the operation of a modern transformer product. When connected to the secondary winding of the load, the working circuit closes, and energy is transmitted almost without loss to the consumer.
Operating modes
Like any converting devices, the transformer has two operating modes:
- the so-called "idle speed";
- load mode.
When idling, the device operates without load and consumes a minimum of power dissipated only in the primary winding. The current in it is also minimal and usually does not exceed 3-10% of the value observed with the connected load. In the second case, a current begins to flow in the turns of the secondary winding, the value of which is inversely proportional to the number of turns in the coil.
In a step-down transformer, the voltage in it is lower, and the current is more. In this mode, power is transferred to the load taking into account thermal dissipation in the transformer core.
main parameters
When considering the parameters of voltage and current converters, it is important to note the transformation coefficient k, defined as I1 / I2 = w2 / w1 = 1 / k. Here w2 and w1 are the number of turns in the secondary and primary windings, respectively. In addition, its characteristics, such as the size of the core window in which the coils are placed, are taken into account.
Another parameter characterizing the transfer properties of a single-phase double-winding transformer in voltage is the same transformation coefficient k, the value of which for a step-down device is less than 1. And vice versa, if k> 1, this product is a step-up transformer. In the absence of losses in the wires of the windings and flow dispersion, this indicator is very simple to calculate. For this, it is most convenient to use a simple calculation algorithm: k = U2 / U1. If there are several secondary windings, the specified parameter should be determined for each of them separately.
Types of transformers and their application
According to the design features of the core, well-known samples of single-phase transformers are divided into rod, ring and armor products. According to the shape of the magnetic circuit used in them, they can be:
- W-shaped;
- Toroidal;
- U-shaped.
Each of these forms is suitable for certain purposes related to the need to obtain specified transmission characteristics.
The largest achievable magnetic coupling (MS) transformers are divided into products with strong, medium and weak interactions. These characteristics largely depend on the design of the product itself and the type of its core.
A single-phase transformer is in demand in areas where it is necessary to coordinate two power circuits with the electrical isolation of each of them.
Product Operation
When operating single-phase converting devices, special attention is paid to the safe handling of them, which is explained by the high voltage present on the primary windings. It is also important to consider the following points regarding the installation and inclusion of transformers in electrical circuits:
- to avoid winding failure (burnout), secondary circuits should be protected from short circuit;
- It is important to monitor the thermal conditions of the core and windings and, if necessary, provide for their cooling.
Caring for a single-phase transformer is reduced to standard procedures, which are provided for by the provisions of current standards.
