How to choose core type for open transformer

The basic structure of an open transformer is mainly composed of a primary winding, a secondary winding and an iron core, and there is insulation between the primary, secondary and iron core. A simple open transformer has a primary winding, a secondary winding and an iron core. Such an open transformer also has only one current ratio.

In order to improve the accuracy of the open transformer, the error of the transformer is generally compensated. In this way, in addition to the above-mentioned primary and secondary windings and cores, some also wind auxiliary coils or add auxiliary cores. Of course, there are also provisions for the selection of iron cores for open transformers.

For example, for high-voltage current transformers above 10KV, in order to facilitate the use, several independent transformer core windings are often installed on a transformer through a common primary winding, insulation and shell to produce multiple currents. Transformer. In this way, a current transformer is equivalent to two or three transformers, two or three secondary can be used to measure or protect the line respectively.

Precision current transformers above class 0.2 are generally made of multiple current ratios, that is, an open transformer has many current ratios, which can be selected when used. The primary or secondary windings of the multiple current ratio transformers are all made in the middle For the tapped type, if the primary (or secondary) winding is unchanged, corresponding to each tapped winding of the secondary (or primary), a current ratio is obtained. Such a combination of primary and secondary windings has many current ratios.

The core of the open transformer has two forms: square and circular: the square is made of silicon steel sheets stacked one by one to form a square core. The advantage is that the coil is convenient to wind. The winding can be wound on the machine in advance and then set on the silicon steel sheet. The core becomes a winding.

At the beginning of the toroidal core, silicon steel sheets are used to punch into the ring pieces and stacked one by one. Now, most of them are directly rolled with silicon steel strips. There is no air gap, the magnetic performance is high, and the rolling is also very convenient. If the winding is evenly wound, the leakage flux is very small. Therefore, precision open transformers of class 0.2 and above all use this kind of band-wound core.