unctions and Core Structure of Toroidal Current Transformers

As a specific type of current transformer, the primary function of a toroidal current transformer is to convert a high primary current into a lower secondary current at a specified ratio, serving purposes such as protection and measurement. Since instruments cannot be directly connected to conductors or busbars carrying high practical currents, the transformer scales the current down to a manageable secondary value, from which the actual primary current can be determined using the transformation ratio.

The operating principle and equivalent circuit of a toroidal current transformer are identical to those of a standard transformer. However, its primary winding is connected in series with the measured circuit and typically consists of very few turns. The secondary winding is connected to low-impedance loads, such as ammeters or relay current coils, operating under near-short-circuit conditions. Both the primary and secondary currents are determined solely by the load on the measured line and are independent of the secondary load of the current transformer.

It is worth highlighting the toroidal core of this transformer. It is manufactured from high-quality, cold-rolled, grain-oriented silicon steel with low core loss and high permeability, available in thicknesses of 0.05mm, 0.08mm, 0.1mm, 0.2mm, 0.23mm, 0.27mm, 0.3mm, and 0.35mm. Due to its continuous, closed-loop magnetic path structure, it exhibits zero magnetic flux leakage and excellent magnetic performance. Furthermore, this toroidal design allows for fast and convenient winding using toroidal winding machines, resulting in high production efficiency.