Role: voltage conversion, current conversion, impedance conversion, isolation, voltage stabilization (magnetic saturation transformer), etc.
1) power transformer: used for transmission and distribution system voltage rise and fall.
2) instrumentation transformers: such as voltage transformers, current transformers, for measuring instruments and relay protection devices.
3) test transformer: can produce high voltage, high voltage test of electrical equipment.
4) special transformers: such as furnace transformer, rectifier transformer, adjusting the transformer, capacitor transformer, phase shifter transformer.
Extended information:
Transformer is composed of an iron core (or magnetic core) and a coil, the coil has two or more windings, which is connected to the power supply is called the primary coil, the rest of the windings called the secondary coil. It transforms AC voltage, current and impedance. The simplest core transformer consists of a core made of soft magnetic material and two coils of unequal number of turns set on the core.
The principle of transformer voltage conversion was first discovered by Faraday, but it was not until the 1880s that it began to be used in practice. The ability to use transformers for AC power was one of the advantages in the competition between DC and AC power that should be output from power farms.
Transformers can convert electricity into a high voltage, low current form and then convert it back again, thus greatly reducing the loss of electricity during transmission and allowing it to be economically transmitted over greater distances. In this way, power plants can be built far away from the place where the electricity is used. Most of the world's electricity goes through a series of transformers before it finally reaches the consumer.
Transformers are used for different purposes in different environments, such as:
1. Increasing the voltage when transmitting over long distances reduces the power loss on the line
2. Reducing the voltage when reaching the area of use meets the needs of the different users of the power supply
3. Using a transformer coupling to change the impedance when impedance matching is carried out
4. The use of isolation transformers can be two-phase power isolation to prevent electrocution accidents
In the rated power, the transformer's output power and the ratio of the input power, called the efficiency of the transformer, that is
The formula η for the efficiency of the transformer; P1 for the input power, P2 for the output power.
When the output power P2 of the transformer is equal to the input power P1, the efficiency η is equal to 100%, the transformer will not produce any loss. But actually there is no such transformer.
Transformer transmission of electrical energy always produces loss, this loss is mainly copper loss and iron loss. Copper loss is the transformer coil resistance caused by the loss. When the current through the coil resistance heat, part of the electrical energy is converted into heat and loss. Because the coil is generally made of insulated copper wire winding, so it is called copper loss.
The iron loss of transformer includes two aspects. One is the hysteresis loss, when the AC current through the transformer, through the transformer silicon steel sheet of the magnetic line of force and its direction and size changes, making the silicon steel sheet internal molecules rubbing each other, releasing heat energy, thus losing part of the power, which is the hysteresis loss.
The other is eddy current loss, when the transformer works. The core of the magnetic lines of force through, in the plane perpendicular to the magnetic lines of force will produce induced currents, due to this current since the formation of closed loop loop, and into the vortex, it is called eddy current. The existence of eddy current makes the iron core heat, energy consumption, this loss is called eddy current loss.
Transformer efficiency and transformer power level has a close relationship, usually the greater the power, loss and output power ratio is smaller, the higher the efficiency. Conversely, the smaller the power, the lower the efficiency.
Reference:
Baidu Encyclopedia-Transformer