ABB KOFA12D3 Indoor current transformers

Secondary winding: With a large number of turns, it outputs a secondary current proportional to the primary current through induced electromotive force for subsequent equipment use.

Insulation and encapsulation

As mentioned in the document, the KOFA series uses epoxy resin casting encapsulation for the primary winding, iron core, and secondary winding, which not only ensures electrical insulation but also fixes the structure to prevent iron core vibration from affecting electromagnetic induction stability.

3、 Job characteristics and application points

The relationship between accuracy and load

The load connected to the secondary side (such as instrument internal resistance, wire resistance, etc.) will affect the accuracy of the current transformer. The document mentions that the rated load range is 2.5-30VA, and excessive load may lead to increased errors. Therefore, it is necessary to select the appropriate rated load based on the parameters of the secondary equipment (such as accuracy levels of 0.2 and 0.5 corresponding to different load requirements).

For example, level 5P10 indicates that under rated load, when the primary current is 10 times the rated value, the composite error does not exceed 5%.

The impact of short-circuit current

When a short circuit occurs on the primary side, a high current will generate a strong magnetic field, which may cause the iron core to saturate and distort the secondary current. The document emphasizes the short-circuit strength parameters (such as short-time current I th, impulse current I dyn), and the design should ensure that the transformer can withstand the thermal and electrodynamic effects of short-circuit current to avoid damage or error exceeding the limit.

The danger of open circuit on the secondary side

The secondary winding must not be open circuited, otherwise when there is current on the primary side, the magnetic flux of the iron core will increase dramatically, and high voltage (up to thousands of volts) will be induced on the secondary side, endangering equipment and personnel safety, and possibly damaging the insulation of the transformer.

4、 Combining with KOFA series in the document

The Implementation of Principles in Structural Design

The KOFA series uses epoxy resin to encapsulate and fix windings and iron cores, reducing external interference and ensuring the stability of electromagnetic induction; The primary terminal is connected with M12 screws, which is easy to install and ensures good electrical contact, avoiding contact resistance affecting the conduction of primary current.

5、Parameter matching and application scenarios

The rated frequency of 50/60Hz is suitable for different power grid requirements, and the secondary current of 5A (1.2A) meets the standard measurement circuit requirements.

For high-altitude areas, by selecting models with higher voltage levels (such as 24kV instead of 12kV), increasing the creepage distance and air gap, preventing insulation breakdown, and ensuring the reliable application of electromagnetic induction principles in special environments.