Accuracy improvement of large current test by split wires of magnetic component winding

High-frequency large current tests are critical in almost all switch-mode power conversion systems. To measure this large current, large size current sensor with large current rating is always needed to bring many disadvantages of bulk volume, less accuracy and high cost. One of the solutions is to use current split technique with the split wires of the winding in magnetic components to measure the current in only one of the strands of the multi-strands Litz wires in magnetic components. In this paper, the mechanics of the current split ratio shifts for different frequencies are revealed. The model is also built and analyzed to find that the leakage inductance ratio between the current testing strand and other strands is the key factor which dominates the current split ratio. Based on the model, a simple method was proposed to improve the current split ratio for different frequencies. The practical tests were performed to verify the method and its current testing precision.