Transient Calorimetric Measurement of Ferrite Core Losses up to 50 MHz

• Published in: IEEE transactions on power electronics Vol. 36; no. 3; pp. 2548 - 2563
• Main Authors: Papamanolis, Panteleimon, Guillod, Thomas, Krismer, Florian, Kolar, Johann W.
• Format: Journal Article
• Language: English
• Published: New York IEEE 01.03.2021; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Conduction; Conductors; Confidence intervals; Core loss; Differential scanning calorimeter (DSC); DSC; Electric conductors; Electrical measurement; FEM; Ferrites; Finite element method; Gaussian distribution; Heat measurement; high frequencies; Loss measurement; magnetic losses; Measurement methods; Measurement uncertainty; MnZn; NiZn; Normal distribution; Ohmic dissipation; Resistance heating; Semiconductor device measurement; Sensitivity analysis; specific heat capacity; Statistical analysis; Temperature measurement; Temperature sensors; Thermal response; Toroids; transient calorimetry; Uncertainty analysis; Very high frequencies; Workflow
• ISSN: 0885-8993; 1941-0107
• DOI: 10.1109/TPEL.2020.3017043

An accurate and fast transient calorimetric ferrite core-loss measurement method is proposed in this article. In contrast to electrical measurements, the accuracy of the calorimetric approach is largely independent of the magnetic excitation and operating frequency. However, accurate values of the thermal capacitance and the temperature of the core under test (CUT) are required. Accurate measurement of the specific heat capacity of the core material can be achieved with a differential scanning calorimeter (DSC) or by using the CUT as a dc electric conductor and measuring its thermal response for known Joule heating. Accurate temperature measurements can be realized with NTC temperature sensors. A thorough uncertainty analysis of the presented method is conducted by identifying the impact of each source of uncertainty in the course of a sensitivity analysis. For the considered reference case (R 22.1/13.7/7.9 toroidal core with N49 ferrite material by EPCOS-TDK - 500 kHz/100 mT), the method achieves a total uncertainty with a worst-case value of less than 12% or, in case of a more realistic approach considering a Gaussian distribution of each source of uncertainty, a mean value of −4.3% with a 95% confidence interval of <inline-formula><tex-math notation="LaTeX">\mathbf {\pm }</tex-math></inline-formula>3.2%. The results are verified by means of finite element method (FEM) simulations and experiments. Furthermore, a step-by-step description of the workflow for preparing and conducting the experiments is provided. The proposed method is tested experimentally and compared to a state-of-the-art electrical loss measurement method for MnZn N87 and N49 ferrite cores of EPCOS-TDK. In addition, it is used to measure the loss-map of the NiZn ferrite material 67 from Fair-Rite for very high frequencies up to 50 MHz, which enables the computation of the material's Steinmetz parameters.