How to choose the core type of open current transformer?

1、The basic structure of open current transformer

Current transformers are mainly composed of primary winding, secondary winding and core, with insulation between primary, secondary and core. Simple open current transformer has a primary winding a secondary winding and a core. Such an open current transformer also has only one current ratio.

In order to improve the accuracy of the open current transformer, the errors of the transformer are generally compensated. In addition to the primary and secondary windings and cores mentioned above, some also wind additional auxiliary coils or add auxiliary cores. Of course, for the open current transformer optional core is also specified.

For example, more than 10KV high-voltage current transformer, in order to use the convenience, often several independent transformer core winding, through a common primary winding, insulation and shell, installed in a transformer, made of multiple current 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.

0.2 level above the precision current transformer, is generally made of multi-current ratio, that is, an open current transformer has many current ratio, for the use of choice, multi-current ratio transformer primary winding or secondary winding are made of the middle tap type, if the primary (or secondary) winding is unchanged, corresponding to the secondary (or primary) of each tap winding, get a current ratio. This way the primary and secondary winding combination, there are many current ratios.

2, the form of open current transformer

Open current transformer core has a square, circular two forms: square with a piece of silicon steel sheet stacked into a square core, the advantage is that the coil winding is convenient, winding can be pre-wound on the machine, and then set in the silicon steel sheet core to become a winding.

In the beginning, silicon steel sheets were used to form circular cores, but now the majority of them are made of silicon steel strips directly rolled into the core. There is no air gap, the magnetic properties are high, and the winding is also very convenient. If the winding is evenly wound, the magnetic leakage is very small. Therefore, more than 0.2 grade precision open current transformers are used with this kind of winding core.

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