Fabien Sixdenier

Power Loss Prediction and Precise Modeling of Magnetic Powder Components in DC–DC Power Converter Application

In power electronics applications, magnetic components are often subjected to nonsinusoidal waveforms, variable frequencies, and dc bias conditions. These operating conditions generate different losses in the core compared to sinusoidal losses provided by manufacturers. In the conception and design stage, lack of precise losses diagnosis has unacceptable effects on systems efficiency, reliability, and power consumption. Since virtual prototyping is used to predict and improve systems behavior before realization, losses and behavior prediction of components is possible. Circuit simulators and their compatible components models are required. This paper is summarized by proposing nonlinear dynamic model of powdered material magnetic core for use in circuit simulators. It includes the materials nonlinear hysteresis behavior with accurate winding and core modeling. The magnetic component model is implemented in circuit simulation software “Simplorer” using VHDL-AMS modeling language. Waveforms and losses of a powder core inductor in a buck converter application are simulated and compared to measured ones. The model is validated for different ripple currents, different loads, and a wide frequency range. DC bias is taken into account in both continuous and discontinuous conduction modes.

Limits and rules of use of a dynamic flux tube model

Purpose - The purpose of this paper is to analyze the main assumption of a dynamic flux tube model and to define its rules of use. Design/methodology/approach - The studied dynamic model lumps together all dynamic effects in the circuit by considering a single dynamic parameter. A physical meaning of this parameter as well as rules of use of the model are elaborated from analyses performed on several samples. A systematic comparison between experimental and calculated results allows to argue the conclusions. Findings - The model gives accurate results when a weak heterogeneity of magnetic data exists, nevertheless, the saturation phenomenon enlarges the validity domain. By considering the losses separation assumption, the model allows to obtain separately an estimation of losses due to classical eddy currents and due to the wall motion effects. Research limitations/implications - The estimation of the models parameter value is still empiric, a work is in progress on this subject. Practical implications - The models implementation in a flux tubes network allows to simulate the dynamic behaviour of industrial actuators having massive cores. Originality/value - A physical interpretation of the parameter associated to the dynamic flux tube model is given. Rules of use of the model are also defined.

Improving reliability of magnetic mutual impedance measurement at high excitation level

Power electronic designers are interested in characterization of the magnetic cores permeability up to 10MHz and at high induction level. To achieve this aim, different experimental setups are used to measure mutual impedance spectra. First, impedance measurement methods are carried out on toroidal wound core of 20 μm nanocrystalline ribbons. Measurement uncertainties are estimated and a confidence factor is introduced as a useful consistency test to improve measurement reliability. Then a lumped equivalent circuit is identified to model electrostatic and magnetic frequency behavior of the device under test. It allows calculating complex permeability spectra over the resonance frequency of the device under test. Finally, we point out the limitation due to high excitation level. According to that, a flux-metric experimental setup is described and elliptical hysteresis-loops are measured. These results allow to consider magnetic linear behavior until a few 10mT and to extend complex permeability calculations to high induction level with good reliability.

A Comparative Study: Dynamic and Thermal Behavior of Nanocrystalline and Powder Magnetic Materials in a Power Converter Application

In the design of such power electronics applications as power converters, lack of precise characterization and diagnosis of losses from components has unacceptable effects on efficiency, reliability, and power consumption. Because passive components, especially magnetic components, are crucially important in power converters, accurate characterization and modeling of magnetic materials is mandatory, to enable realistic prediction of their behavior under variable operating conditions. Temperature is one such condition that induces major changes in a component’s behavior by modifying the material’s magnetic properties. In the work discussed in this paper we investigated the magnetic and thermal behavior of nanocrystalline and powder materials in a DC–DC converter application. Core loss measurements under variable conditions were performed on toroid-shaped samples. Measured results were analyzed for different frequencies, flux densities, and temperatures.

Temperature-Dependent Extension of a Static Hysteresis Model

Some soft magnetic materials are strongly dependent on the temperature, because of their low Curie temperature. In order to predict their behavior in electrical devices, engineers need hysteresis models able to consider the temperature. This paper is an attempt to consider the temperature in an existing model of static hysteresis through its parameters. Variations of some parameters with temperature are issued or build thanks to the literature. At the end, all needed parameters have an analytical law versus temperature. The simulation results are compared with measurements and discussed.

Comparison between numerical and analytical methods of AC resistance evaluation for Medium Frequency Transformers: Validation on a prototype

In the future, Medium Frequency Transformers (MFT with a frequency range 5 kHz to 100 kHz) will be major components in DC-DC converter applications, for both Medium Voltage Direct Current (MVDC) and High Voltage Direct Current (HVDC) networks. Importantly, the corresponding power losses should be accurately calculated in order to reach performance targets (very high efficiency). This paper reviews the most known analytical models which are used to calculate the medium frequency resistance for several winding technologies. In order to qualify these models in a future design flow, we compare the analytical model results with measurements and 3D finite element (3DFE) electromagnetic simulations. The adopted design flow-chart has been tested on a 17 kHz - 180 kVA prototype transformer that will be used in a Dual Active Bridge (DAB).

Simulation of Low-Nickel-Content Alloys for Industrial Ground Fault Circuit-Breaker Relays

The aim of this paper is to simulate the performances of a ground fault circuit-breaker (GFCB) relay with new low-nickel-content alloys. Indeed, in the construction industry, the materials become more expensive as their nickel content increases. Moreover, the demand for nickel is particularly sensitive to the economic conjuncture. Therefore, an original electromagnetic relay model has been developed and validated in different working conditions (current amplitude, frequency, and temperature). A dedicated magnetic characterization of materials is needed, using basically a usual and industrial GFCB relay for reference and design data in modeling. First, the magnetic model of the relay is built and checked against experimental data. The simulation may predict the tripping current threshold of the relay. On the other hand, new low-nickel-content alloys for relay parts are studied in this framework, thanks to the developed model. The effects of temperature on the magnetic properties of the candidate materials and the electrical performances of the virtual relays are presented. The results, analysis, and conclusions are given. Finally, a first attempt to predict the economic gain obtained with a change of material is made.

Experimental Analysis of Air Jets for Sorting Applications

Pulsed air jets are used in the industry to eject objects in sorting operation and understand the jet establishment and its spatial characteristics is important to optimize the application. This paper presents a first experimental analysis of jets issued from a high speed solenoid valve in terms of pressure, temperature, and velocity. Results will be first shown for steady state flows at different pressure conditions inducing subsonic or supersonic air jets and compared to the literature. For a subsonic jet, the results confirm the topography proposed in the literature. For the supersonic jets, a subsonic topography was identified after the supersonic zone. These supersonic jets have a constrained diameter which is appreciated in order to perform sorting with precision. Then, first unstationary experimental results will be presented and commented. This first measurement of the jet development is encouraging, since it was possible to identify the different delays linked to the propagation time from the valve outlet to the measurement point on opening and closing.Copyright