Three-phase transformer

Three-phase transformers (three-phase transformers) or transformers in general are required to increase or decrease AC voltages. Further information under three-phase transformer.

A transformer consists of a magnetic circuit, known as the core, and has at least two windings through which current flows. The winding facing the electrical voltage (mains voltage) is called the primary side, the side with the load (separate winding) and the electrical load is called the secondary side. The manufacturing technology for the core and the quality of the transformer core material used have an effect on the magnetic circuit. Ideally, the magnetic circuit should generate low eddy current losses and low remagnetization losses (hysteresis losses). Another aspect is the resistance in the winding. Winding losses can only be reduced with a layered and ordered winding on the primary side and the secondary side of the coil and the best winding material.

The power rating of a transformer is expressed in VA or kVA (VA stands for volt-ampere and is the unit of measurement for apparent electrical power, kVA for kilovolt-ampere).

With the exception of silver, copper has the best conductance with γ = 56 (aluminum γ = 36). Aluminum follows with a gap of around 35 percent. Copper is therefore the best precious metal and aluminum “only” the second best of the technically and economically usable conductor materials. All other metals cannot be considered as conductors and alloys generally have a considerably lower conductivity than pure metals. Silver or gold are completely ruled out due to their high price.

In principle, a three-phase transformer consists of three single-phase transformers. It therefore combines three individual transformers, which are required for a three-phase system, into one transformer. The structure of a normal single-phase transformer therefore remains largely the same.
A transformer essentially consists of two or more coils and a common iron core. The windings of a transformer are usually made of insulated copper wire and are wound on the iron core. The input voltage is applied to the primary winding of the transformer. This is why the coil on the primary side is often called the primary coil. The alternating voltage on the primary coil creates an alternating magnetic field due to inductivity. The magnetic flux passes through the secondary coil with the help of the iron core. The output voltage can therefore be taken from the secondary side of the transformer. Corresponding to the primary side, the coil on the secondary side is called the secondary coil. The winding ratio of the primary and secondary coil defines whether the output voltage is lower or higher than the input voltage. If the number of turns of the secondary coil is greater than that of the primary coil, the output voltage is greater than the input voltage. However, if the number of turns of the secondary coil is lower, the output voltage is lower than the input voltage. If both coils have the same number of turns of wire wound around them, the output voltage is equal to the input voltage. A transformer works mainly with alternating voltage. The ratio of the number of windings is decisive for the change in power, voltage or current. N1/N2. It is important to note that the transformer can either increase or decrease the voltage or current. The respective counterpart will then decrease or increase to the same extent.
The difference between single-phase and three-phase transformers is that the primary and secondary sides each consist of separate windings. The differences also lie in the reduced design. If the connections of the primary windings and the secondary windings of three single-phase transformers are permanently connected, these transformers can be used in the three-phase network. The advantage of a three-phase transformer is the reduced size and the associated cost benefits in purchasing as well as the reduced power loss during operation.

Three-phase transformers are the basis of the power supply and are used for the electrical distribution and transmission of current and voltage and are used in every industrial plant worldwide.