An Impedance Converter-Based Probe Characterization Method for Magnetic Materials’ Loss Measurement

As an essential component in power applications, magnetic cores and their design play an important role in achieving high efficiency and high power density. Accurate measurement of the core loss is important for inductor and power converter optimization. Loss measurement depends on exactly determining the phase angle between the voltage and the current. However, measurement errors can be introduced due to the discrepancies in propagation delays in the voltage and current sensors. In addition, the propagation delay is frequency-dependent but has a large influence in the MHz range and above. Previously, several methods have been proposed to compensate for this discrepancy, but they are time-consuming and can result in large measurement errors. In this article, a characterization method for core loss based on a vector network analyzer (VNA) and an impedance converter is proposed to accurately measure the phase discrepancies between voltage and current sensors. The proposed method is experimentally verified up to 15 MHz with a three-coil test setup.

I. Introduction

Magnetic components (e.g., inductors and transformers) are critical components in power electronics applications [1]–[4]. Due to their high permeability, ferrites are used to reduce the physical dimension of these passive components. However, ferrites are nonlinear. Losses can be influenced by the temperature, frequency, and magnetic flux density [5]–[8]. To optimize the performance of inductors and transformers with respect to loss, size, power density, and thermal characteristics, accurate loss measurements for these magnetic materials are essential.