Core Loss Measurements Research Articles

A Novel DC Differential Method for High Frequency Core Loss Measurement

A Novel DC Differential Method for High Frequency Core Loss Measurement

Core Loss Measurements of Ni-Zn Ferrites by Resonant Method and Loss Separation based on Magnetization Process

Core Loss Measurements of Ni-Zn Ferrites by Resonant Method and Loss Separation based on Magnetization Process

Improved Oscillation Method for High-Frequency Magnetic Core Loss Measurement

Improved Oscillation Method for High-Frequency Magnetic Core Loss Measurement

Accuracy Investigation of High-Frequency Core-Loss Measurement for Low-Permeability Magnetic Materials

Accuracy Investigation of High-Frequency Core-Loss Measurement for Low-Permeability Magnetic Materials

Core Loss Equivalent Resistance Modeling of Small- and Medium-Sized Converter-Fed Induction Motors Considering Supply and Spatial Harmonics

In order to estimate the core loss resistance of converter-fed induction motor accurately and efficiently, an analytical piecewise variable-coefficient core loss model is proposed. By introducing two voltage harmonics related coefficients, the influence of converter harmonics on core loss is simply and effectively considered. In addition, the surface and pulse loss caused by slot harmonics and the additional harmonic core loss caused by harmonic magnetic potential of stator winding under load condition are also considered. Based on the proposed model, an advanced core loss equivalent resistance model of converter-fed induction motor considering supply and spatial harmonics is proposed. The effectiveness of the proposed model is validated by comparisons with the measured core losses of 5.5 kW induction motor under no-load condition. In addition, compared with the finite element method under load condition, the proposed analytical model reduces the computational time significantly while maintaining high accuracy.

Using electron energy-loss spectroscopy to measure nanoscale electronic and vibrational dynamics in a TEM.

Electron energy-loss spectroscopy (EELS) can measure similar information to x-ray, UV-Vis, and IR spectroscopies but with atomic resolution and increased scattering cross-sections. Recent advances in electron monochromators have expanded EELS capabilities from chemical identification to the realms of synchrotron-level core-loss measurements and to low-loss, 10-100meV excitations, such as phonons, excitons, and valence structures. EELS measurements are easily correlated with electron diffraction and atomic-scale real-space imaging in a transmission electron microscope (TEM) to provide detailed local pictures of quasiparticle and bonding states. This perspective provides an overview of existing high-resolution EELS (HR-EELS) capabilities while also motivating the powerful next step in the field-ultrafast EELS in a TEM. Ultrafast EELS aims to combine atomic-level, element-specific, and correlated temporal measurements to better understand spatially specific excited-state phenomena. Ultrafast EELS measurements also add to the abilities of steady-state HR-EELS by being able to image the electromagnetic field and use electrons to excite photon-forbidden and momentum-specific transitions. We discuss the technical challenges ultrafast HR-EELS currently faces, as well as how integration with in situ and cryo measurements could expand the technique to new systems of interest, especially molecular and biological samples.

GaN-based cryogenic temperature power electronics for superconducting motors in cryo-electric aircraft

Climate change has spurred a shift to electric transportation, but aviation faces challenges with electric energy storage and propulsion. Cryogenically cooled superconducting motors, along with cryogenically cooled power electronics, offer a solution to increase the efficiency and power density of electric aircraft. This paper evaluates the feasibility of cryogenic power electronics by characterising new technologies (GaN, nanocrystalline) using new experimental techniques. It is found that the on resistance reductions of GaN E-high electron mobility transistors at cryogenic temperatures depend on the maximum blocking voltage of the device, and the size of the gate resistor for ohmic p-GaN devices. Different types of nanocrystalline cores are shown to vary greatly in their behaviour at cryogenic temperatures, which is measured using a modified core loss measurement circuit. Further analysis shows that the losses of a GaN based cryogenic inverter could potentially halve that of an equivalent Si based inverter.

Core loss measurement and comparative analysis for soft magnetic materials under complex non-sinusoidal excitations

With the advancement of wide-bandgap power devices, the power electronics equipment is developing toward higher switching frequencies and more complex switching modes in recent years. Accurate prediction of the core loss for magnetic components has been emphasized as the excitations of magnetic materials varying depending on the operating mode of the power supplies. Therefore, this paper presents the results of an extensive core loss study performed on nanocrystalline alloy (FT-3KL), amorphous alloy (1K101) and ultra-thin oriented silicon steel (GT-50). Firstly, an automatic setup for core loss measurement of soft magnetic materials fed by a full-bridge inverter based on silicon carbide (SiC) MOSFET is proposed. Then, the effects of switching oscillations from the inverter and the characteristic parameters of complex non-sinusoidal excitations on the core loss are analyzed comparatively. The core loss shows different regular distributions with the change of each characteristic parameter of excitations respectively. However, the regular distributions will be influenced by the high-frequency switching oscillations, which makes the prediction of core loss more complicated. This paper can provide a reference for the development of high-precision core loss model and performance optimization of power electronics equipment.

Effect of grain size on the core loss of nanocrystalline Fe86B13Cu1 prepared by ultra-rapid annealing

Nanocrystalline alloy samples with the same chemistry (Fe86B13Cu1) but with a range of mean grain sizes were prepared in order to investigate the effect of the grain size (D) on the core losses in nanocrystalline alloys. The core loss was measured on an Epstein frame in a frequency range between 10 Hz and 30 kHz. The measured core loss was separated into 3 parts, i.e. the hysteresis loss, classical eddy current loss and the excess loss. The classical eddy current loss is only a minor component due to the small thickness and moderately high electrical resistivity of the samples. Both the coercivity and the cycle hysteresis loss are found to follow roughly a D3 dependence. The excess loss at the maximum polarization (Jm) between 0.6 and 1.0 T is described universally by a simple power dependence of (Jm·f)n with an exponent of about 1.4 over a wide frequency (f) range between 10 Hz to 30 kHz. The excess loss at low frequencies appears almost independent of the grain size. Thus, the grain size effect on the total loss at low frequencies is attributable to the change in the hysteresis loss which reflects the static coercivity. However, the excess loss at 30 kHz shows a clear increase with an increase in D, indicating that the excess loss also becomes influential to the grain size dependence of the total core loss at high frequencies.

High Performance Planar Magnetics Based on an Unbalanced-Flux Approach

This paper presents a new design concept to increase the efficiency and the power density of planar magnetics. In contrast to the existing magnetics, which are built using the balanced magnetic flux density design, the proposed design concept generates unbalanced magnetic flux density across the different parts of the magnetic core. The theoretical analysis shows that the core loss of the unbalanced-flux design can be reduced by more than 50% compared to the existing one. The core loss reduction brings several benefits to planar magnetics such as: high power capability, better thermal performance and wider safe operating area (SOA). The proposed design is experimentally evaluated and compared with the balanced-flux design. The experimental results are in good consistency with its theoretical counterparts. The measured core loss are decreased by more than 50% and the power density is increased by more than 250%.

A Review of Magnetic Core Materials, Core Loss Modeling and Measurements in High-Power High-Frequency Transformers

High-frequency transformers (HFTs) are the indispensable component in isolated high-power dc-dc converters which have been the basic building blocks for solid-state transformers. To ensure high efficiency, high power density and high reliability, careful selection, design, modeling and evaluation are necessary for the magnetic core of an HFT. However, due to the nonlinear characteristics and the complex physical mechanism, magnetic cores have always been regarded as the focus and difficulty. This paper systematically reviews magnetic core materials commonly used in HFTs, core loss modeling methods based on classical Steinmetz equation (SE), and advanced core loss measurement techniques. Pros and cons for the magnetic materials, modeling and measurement methods are comprehensively analyzed and summarized to provide a sufficient application insight.

Improved Current Shunt Characterization Method for Core Loss Measurement

With the increasing switching frequencies and power densities in modern power converters, magnetic core losses are becoming more essential for efficiency and thermal optimization. Traditionally, the two-winding method suffers from sensitivity to phase error in practical measurements; this is mainly created by the unknown phase shift of a current-sensing resistor. Several methods have been developed to characterize the phase shift of a current shunt resistor; however, the load effects of oscilloscopes are ignored. As a result, the corresponding phase shift can be significantly underestimated. This article proposes an improved method for phase shift extraction of a current shunt to solve the problem. The effectiveness of the shunt characterization method is experimentally verified up to 50 MHz. Benefits from the proposed method, the time-consuming component tuning process is not required for core loss measurement. A measurement verification at 10 MHz shows its validity. Finally, a current shunt implemented with a coaxial resistor array is designed with a phase shift of 0.05 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$^\circ$</tex-math></inline-formula> at 10 MHz and a parasitic inductance as low as 42 pH.

Eddy Current Loss Model for Ferrite Ring Cores Based on a Meta-Material Model of the Core Properties

A model for estimating the total eddy current losses in ring ferrite cores is proposed, which is based on a microstructure model of the electrical parameters of the material (conductivity and permittivity) and on the solution of the wave equations in the core. The presented model, combined with state-of-the-art estimation of the hysteresis losses, gives good agreement with the core loss measurements, over a wide range of frequencies (10–700 kHz).

Efficient and accurate phase-measurement method for core-loss characterization.

Accurate core-loss characterization is essential to push the power density of power converters to their limits. However, existing core-loss measurement methods still have some limitations, such as a slow test speed and a complex probe calibration procedure. In particular, accurate phase-difference measurement is time-consuming because a fast Fourier transform analysis with a kHz-range frequency interval is typically applied to reduce the influence of noise. An automated measurement system for magnetic core-loss characterization is described in this paper. An accurate phase-detection block with programmable attenuators is developed to measure the phase difference between voltage and current waveforms. The proposed system considerably improves the test speed while providing comparable accuracy to the existing method.

In-Situ Measurement and Investigation of Winding Loss in High-Frequency Cored Transformers Under Large-Signal Condition

This paper presents an in-situ measurement method to accurately characterize the winding loss in high-frequency (HF) transformers, which is challenging to quantify in power electronics applications. This approach adapts the reactive voltage cancellation concept to measure the complete winding loss in HF transformers with the presence of the magnetic core and the load on the secondary side, while this concept was originally brought up for core loss measurement. As an in-situ method, the proposed testing method can factor in the non-linear winding loss elements impacted by the magnetic field interaction between the windings and the core under the large-signal operation, which are not properly assessed in existing approaches. The presented method significantly reduces the sensitivity of the measurement errors linked to the probe phase discrepancy, since the resistive winding loss is well separated out from the core loss. The acquired experimental results are compared and verified with other common empirical measurement methods and three-dimensional (3D) finite element analysis (FEA). As the finding, the measured winding AC resistance is found to be correlated with the load level. Furthermore, treating the complex winding loss and core loss as a black-box problem, this paper proposes a &#x201C;total loss map&#x201D; as an engineering solution to practically distribute the measured loss data of magnetic components to the end-users to enable quick and accurate loss estimation&#x002F;modelling.

Measurement and Modeling of Rotational Core Loss of Fe-Based Amorphous Magnetic Material Under 2-D Magnetic Excitation

Fe-based amorphous magnetic materials are recently attracting strong interests for constructing high-power density and high-efficiency rotating electrical machines due to their attractive properties, such as low core loss and high magnetic saturation. Accurate measurement and modeling of the rotational core losses of the core magnetic materials, and the corresponding patterns of rotating magnetic flux density ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$B$ </tex-math></inline-formula> ) and magnetic field strength ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$H$ </tex-math></inline-formula> ) are important for the analysis and design of electrical machines. This article presents the measurement of rotational core loss of a Fe-based amorphous magnetic material (amorphous 1k101), and its corresponding modelings under two-dimensional (2-D) circularly and elliptically rotating magnetic fields. In addition, an improved and simplified analogical model of rotational hysteresis loss is proposed for such magnetic materials. The circular and elliptical <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$B$ </tex-math></inline-formula> loci and the corresponding <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$H$ </tex-math></inline-formula> loci have been investigated to acquire the perception of anisotropy and permeability of the amorphous materials. The proposed theory and models are experimentally verified.

Core Loss Analysis of Soft Magnetic Composites Based on 3D Model Considering Temperature Influence

Soft magnetic composite (SMC) is composed of ferromagnetic particles surrounded by an electrical insulation layer. The unique structure of SMC makes it difficult to calculate the eddy current loss of SMC. In addition, the temperature rise in the working condition affects the magnetic properties of the material, which makes it necessary to consider the temperature effect in the process of core loss prediction. In this paper, a magnetic property test platform that considers the influence of temperature is established. The core losses of the SMC ring sample were measured at 20–100 °C, and the experimental results show that core loss decreases as the temperature increases. Then, based on the method of using the SMC model to calculate the core loss, the effect of temperature increase on hysteresis loss and eddy current loss was analyzed, and the existing model was improved to consider the effect of temperature on the core loss. Finally, the measured core losses at different temperatures were compared with the calculated ones, and it is shown that the improved model considering the influence of temperature agreed well with the experimental results, which improves the accuracy and convenience of core loss calculation for the electromagnetic device with SMC cores.

A Novel In-Situ Measurement Method of High-Frequency Winding Loss in Cored Inductors With Immunity Against Phase Discrepancy Error

Evaluating the high-frequency winding loss accurately is crucial for the design of modern high-frequency power converters. This paper proposes a novel experimental method to accurately measure the in-situ inductor winding loss, which separates out the winding loss from the core loss through the reactive voltage cancellation concept. The proposed in-situ measurement can account for the complete winding loss including impacts from non-ideal field distributions by testing the inductor with the core attached, e.g., the winding edge effect, bypass flux, fringing flux, and the non-linear dynamic behaviour of the core, which cannot be well modelled with the existing analytical or simulation methods. This method has immunity against the probe phase discrepancy error, since it is designed to measure a pair of voltage and current that are in phase. This approach can be considered as the first attempt of applying the reactive voltage cancellation concept in measuring winding loss, while this concept was originally brought up for core loss and applied for core loss measurement only. By performing a Triple Pulse Test (TPT) procedure, the winding losses under practical large signals with dc-bias and rectangular voltage can be evaluated with the proposed testing circuit. The proposed approach is compared and verified against the conventional methods relying on ( <xref ref-type="disp-formula" rid="deqn1" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1</xref> ) small-signal impedance measurements and FFT analysis ( <xref ref-type="disp-formula" rid="deqn2-deqn3" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</xref> ) in-situ measurement with the two winding method to exclude the core loss. The presented method provides a foundation for the accurate in-situ evaluation of winding loss covering all the large-signal and non-linear effects.

A New Method for Offline Compensation of Phase Discrepancy in Measuring the Core Loss With Rectangular Voltage

Nowadays accurate characterization of the magnetic component losses becomes increasingly important in the design stage of power converters. As the main challenge in characterizing a magnetic component, the core loss is commonly measured through the two winding B-H loop measurement method that is susceptible to the phase discrepancy error, especially for low-permeability, low-loss cores. This paper, therefore, proposes a new offline method to compensate the phase discrepancy error in high-frequency core loss measurement under rectangular voltage excitation. In the post-processing of measured waveforms, the phase discrepancy is compensated by shifting the measured current horizontally to align with a reference phase angle, which is found from an offline impedance sweep on the component-under-test and FFT analysis. As a result, the testing voltage and current waveforms can be measured without considering deskew at the time of measuring. Additionally, this method is more accurate than calibration methods considering a fixed frequency response (e.g., a deskew fixture), because it considers the frequency response across the whole spectrum. The proposed approach can be well applied for typical PWM converters with switching frequencies up to hundreds of kilohertz, for which the effective voltage harmonics extend to a few megahertz range that can be well evaluated with an impedance analyzer. The presented method is experimentally verified against the existing partial cancellation method which is immune to phase discrepancy error.

Transient Calorimetric Measurement of Ferrite Core Losses up to 50 MHz

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 $\mathbf {\pm }$ 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.