Scientific paper ID 2806 : 2026/4

A current transformer (CT) reproduces the primary current in its secondary circuit with a defined transformation ratio and phase displacement. This study presents the design and construction of a 5/1 A split-core CT. The objective is to select a winding and magnetic-core configuration that provides a secondary current close to 1 A at a primary current of approximately 5 A and to perform a preliminary experimental assessment of the influence of the number of turns, conductor arrangement, and split-core closing quality. The paper clarifies the basic relationships for ideal and practical CTs, provides a first-order estimate of the excitation current, and compares technological measurements obtained for several winding configurations. Configuration 6 gives the closest value to the target current ratio of 0.2, with measured currents of 5.17 A on the primary side and 1.10 A on the secondary side. Magnetic properties, secondary burden, and split-core closure remain important for further optimization. Accuracy-class verification under IEC 61869-2 s additional ratio and phase tests at specified burden, frequency, and current levels, these development measurements do not establish an accuracy class.