How is the principle of EI transformer compared with that of other transformers?

Static electromagnetic devices that convert electrical energy and transfer electrical energy from one circuit to another are called toroid transformers. EI transformer is one of the electronic transformers, which is defined according to the shape of the iron core. Because the iron core of EI transformer is superimposed by "e" and "I", it is called EI transformer. EI transformer is generally a power frequency (low frequency) transformer (50Hz or 60Hz), power transformer and some audio transformers are also EI, such as those used in acoustics.
The no-load loss of dual-c transformer is much lower than that of EI transformer, and the assembly is as simple as that of EI transformer. The advantages of oriented silicon steel can be fully utilized. The magnetic density is higher than that of EI, and the bulk density is higher than that of EI transformer. There is only one drawback, noise. When the double-C joint rusts, the noise becomes a mystery. Dual-c transformers are also obsolete.

The cross section of ring type transformer is rectangular or square. The annular core is wound, which can make full use of the advantages of oriented silicon steel. In addition, the magnetic circuit of the wound core is small, the magnetic density can be relatively high, the volume power density is almost twice as high as EI, and the no-load loss is only 1/10 or even lower than EI. In addition, with the popularity of the annular winding machine, the annular transformer has been widely used.
WB transformer has the shortest magnetic circuit and can make full use of the advantages of oriented silicon steel. However, due to the large gap between winding and iron core, the magnetic leakage is relatively large, and the efficiency is similar to that of ring transformer. WB type transformer was popular in Japan for a period of time. It needs to be wound first and then the iron core is rolled. It is the most difficult to make and belongs to the eliminated variety.
The R-type transformer is developed to reduce the difficulty of winding. It has a circular section and can make full use of the advantages of oriented silicon steel. In addition, it is easy to wind the wire by rotating the skeleton. It will become popular. Most of the high-power transformers are R-type. Although the magnetic leakage of R-type transformer is small in theory, its magnetic circuit is long and its actual magnetic density is similar to that of ring type transformer. Due to the large number of coil layers, the actual efficiency is slightly inferior to that of the ring.