What is the difference between a three-phase transformer group and a three-phase transformer (core type)?

What is the difference between a three-phase transformer group and a three-phase transformer (core type)?

They are different in the magnetic circuit system. The three-phase transformer group is connected by three single-phase transformers connected to three-phase circuits. Each phase main magnetic flux has a single-phase magnetic circuit, and each magnetic circuit is independent of each other. The three-phase transformer evolved from a three-phase transformer group, which simply combines each core column of a phase-rich single-phase transformer into a common core column. Since the three-phase main magnetic flux is symmetrical, that is, the magnetic flux passing through the common core column is zero, the common core post can be eliminated, so that the three-phase core post is finally arranged in the same plane. Thus, the main magnetic flux of each phase is closed by the magnetic circuit of the other two phases, so the magnetic circuit system is related to each other. The core of the three-phase transformer has three legs. Each core column is provided with one or two windings, and the first and second windings are respectively connected into a star form triangle, which is separately connected with the power source and the load.

The three-phase transformer group is irrelevant because the magnetic circuits of the phases are mutually independent. Therefore, when a single fault occurs, the other two can be connected to form a V-type normal power supply.