Transformer – a simple device for converting voltage or current. It is so common in the industrial and household appliances, that would seem to explain how it works, to what everybody knows. However, such a simple device, in many cases, causing issues. For example, the three-phase transformer differ from a single-phase? Why is it needed? How could it possibly be?
Types of transformers
These devices can range from the huge substations to literally microscopic in complex electronic devices and radio engineering. They differ in the frequency of the supply voltage, the transformation ratio and the utility. The biggest are used to transmit electricity over long distances. With their help, the first voltage increases (input line) and then decreases (at the point of connection of consumer networks). In General, the main types are only three:
Three-phase transformer can refer to any of these types, if it is designed to work in three-phase network, invented by the great Russian electrician Dolivo-Dobrovolsky, who proved its feasibility. It differs from the single-phase counterpart is that it represents the threefold repetition. He has at least three input and three output windings. Structurally, each pair may be mounted on its own magnetic core or have shared, it does not matter. Each winding of the three-phase transformer is calculated for a certain load current, depending on a selected cable section and the size of the magnetic core made of ferromagnetic material. All three deserve a separate, though not very detailed examination.
The most common type serves to increase or decrease the voltage. Inside each substation – district, house, city, village or township, is a three-phase transformer that provides power to some part of the population, living sometimes on multiple streets, or enterprise. It consists of six windings, three primary (with lots of turns) and three secondary (smaller). The primary winding is supplied with high voltage, measured in kilovolts, and is removed from the secondary consumer (industrial: 380 V, also called linear or interfacial or phase 220V between neutral and a phase). Connection three-phase transformer can be done in two ways (“triangle” or “star”).
Substations are installed for economic reasons, to reduce losses when transporting energy. The fact that the less current, the less heating of wires of transmission lines, the dependence is quadratic. Increasing the voltage five times, for example when the same transmitted power can reduce the current in the same amount of time, and losses will decrease by 25 times.
Measurement of parameters of electric circuit – the most important task of energy. If you want to define currents of relatively small quantities of special complications invented a simple and reliable devices as magneto, and digital. Another thing, if the current reaches tens of amperes or even hundreds. There is already required a three-phase current transformer, the secondary windings of which it is possible to obtain multiple reduced values measured regular standard ammeters. Theoretically, of course, you can make a device that can withstand a huge current and have ultra low resistance, but in this case, the frame and the entire mechanism will be cyclopean. And the cost of this ammeter will be comparable to the price of the rest of the substation equipment, together.
Its fundamental device they are no different from the power, moreover, on purpose too, they need to provide power. Another thing is that the nature of the load have specific. Typically, the required power is very big and they are unevenly distributed in time. For example, three-phase welding transformer are designed for continuous operation in almost short circuit with very low resistance connected to the output windings. While the load is pulsed and unbalanced character. About the same, little is acceptable for a conventional transformer mode, the device is made to power low-impedance and very powerful electric furnaces and inductors hardening by high frequency currents.