A static hysteresis model for power ferrites

Basso and Bertotti's physics-based, yet simple, static hysteresis model is brought to the power electronic community as an alternative for simulation of magnetic components embedded in a power electronic converter. The model is reviewed and its equations cast in application/simulation-oriented forms. It is then revised to better characterize the very soft saturation behavior of commercial power manganese-zinc (MnZn) ferrites. The procedures to extract the model parameters from voltage and current measurements are described. The improved models have been verified against experimental data for major and minor hysteresis loops of three commercial power ferrites     

A generalized dynamic circuit model of magnetic cores for low- andhigh-frequency applications. II. Circuit model formulation andimplementation

This paper describes the formulation and implementation of a generalized dynamic magnetic core circuit model suitable for both low- and high-frequency applications. The behavior of magnetic cores with any arbitrary flux waveforms is modeled by a simple ladder network consisting of nonlinear inductors and resistors. The nonlinear B-H loop and the hysteresis loss are incorporated in distributed nonideal inductors and calculated by the Preisach scalar model of magnetic hysteresis. The eddy current and anomalous losses are accounted for by the generalized nonlinear equivalent resistors reported in Part I of the paper. The transmission line modeling method is employed to solve the nonlinear state equations. Numerical aspects and software implementation of the model are discussed. The generalized model has been verified by simulations and measurements at both low- and high-frequency operations     

AC losses in HTS tapes in applied longitudinal magnetic fields at variable temperatures

In most power devices, the conductor is carrying an ac transport current while it is exposed to an ac magnetic field transverse to the current path. In certain applications, such as power cables or a control winding in a controllable reactor, the conductors are exposed to a magnetic field component longitudinal to the tape axis that is parallel to the current path. To create an improved base for the design of such power devices it is of interest to study the losses in high-temperature superconductor tapes due to longitudinal field in detail. We have investigated the losses at several temperatures of a nontwisted multifilamentary Bi-2223 tape when it was exposed to a longitudinal magnetic field. The losses were measured with a calorimetric method and the results were compared with the critical state hysteresis loss model. The hysteresis losses are dominating at power frequencies (50, 60 Hz) in the investigated field range 2-200 mT and are accurately described by the critical state hysteresis model.     

Recent Developments in Fault Detection and Power Loss Estimation of Electrolytic Capacitors

This paper proposes a comparative study of current-controlled hysteresis and pulsewidth modulation (PWM) techniques, and their influence upon power loss dissipation in a power-factor controller (PFC) output filtering capacitors. First, theoretical calculation of low-frequency and high-frequency components of the capacitor current is presented in the two cases, as well as the total harmonic distortion of the source current. Second, we prove that the methods already used to determine the capacitor power losses are not accurate because of the capacitor model chosen. In fact, a new electric equivalent scheme of electrolytic capacitors is determined using genetic algorithms. This model, characterized by frequency-independent parameters, redraws with accuracy the capacitor behavior for large frequency and temperature ranges. Thereby, the new capacitor model is integrated into the converter, and then, software simulation is carried out to determine the power losses for both control techniques. Due to this model, the equivalent series resistance (ESR) increase at high frequencies due to the skin effect is taken into account. Finally, for hysteresis and PWM controls, we suggest a method to determine the value of the series resistance and the remaining time to failure, based on the measurement of the output ripple voltage at steady-state and transient-state converter working.      

Model of the flux flow losses in a high-temperature superconducting tape exposed to both AC and DC transport currents and magnetic fields

Recent progress in the high-temperature superconductor technology will probably be of importance for future power applications. In these applications, the power loss is a very important quantity, which has to be described in a relevant manner to obtain an optimum utilization of the conductor. In most power applications the magnitude of the transport current will be quite close to the critical current. In addition to the hysteresis losses, for such high currents, the flux flow losses have to be taken into account. We present a semiempirical model of the flux flow losses in a tape shaped conductor, based on measurements and reasonable physical assumptions. The model gives the flux flow loss as function of temperature, a transport current consisting of both ac and dc components and an applied homogeneous magnetic field with an amplitude proportional to the current.     

Dynamic model of magnetic materials applied on soft ferrites

A behavioral model of magnetic materials is presented. This model takes into account both hysteresis and dynamic phenomena. It predicts B(H), φ(t) and dφ(t)/dt characteristics, and a few pieces of experimental data are needed to identify its parameters. In this paper, the authors propose to validate the model for some typical applications encountered in power electronics. Results obtained are very satisfactory     

Thermal modeling of high frequency DC–DC switching modules: Electromagnetic and thermal simulation of magnetic components

This work focuses on the accurate thermal modeling of magnetic components for power converters. The inductors of a 1.8 MHz DC–DC switching converter are simulated using the Finite-Element (FE) approach with a three-step procedure: (i) electrical simulation for Joule power loss; (ii) electromagnetic simulation for core losses and eddy currents; (iii) thermal simulation for temperature distribution calculation. The magnetic component models can be used in the full converter FE thermal simulation for design optimization and estimation of reliability hazards.     

Harmonic Impact on Distribution Transformer No-Load Loss

The losses in European Union distribution transformers are estimated at about 33 TW ·h/year, whereas reactive power and harmonic losses add a further 5 TW ·h/year. The reduction of distribution transformer no-load loss is particularly important as the ratio of no-load to load losses is nearly three. In this paper, the no-load operation of wound-core transformers under sinusoidal and distorted supply-voltage conditions is investigated. For that purpose, a 2-D nonlinear transient finite-element analysis taking into account hysteresis has been developed. The hysteresis model is based on a modified Jiles-Atherton representation, and the proposed analysis is compared to experimental data.     

Developing a Simplified Analytical Thermal Model of Multi-chip Power Module

The study of the thermal behavior of power modules has become a necessity regarding the known rapid development in modern power electronics, and the prediction of temperature variation has generally been performed using transient thermal equivalent circuits. In this paper we have developed a simplified analytical thermal model of a power hybrid module. This analytical method is used to evaluate the thermal parameters of a device. The model takes into account the thermal mutual influence between the different module chips based on the analytical method. The thermal interaction between components is dependent on the boundary condition, the dissipated power value in the different components and the number of operating chips constituting the module. This effect is modelled as a source energy and a thermal resistance simply computed tanks to reasonably low measurement applied on the module. The derived thermal models offer an excellent trade-off between accuracy, efficiency and CPU-cost.     

A three-phase to three-phase series-resonant power converter withoptimal input current waveforms. I. Control strategy

A control strategy for multiphase-input multiphase-output AC to AC series-resonant (SR) power converters is presented. After reviewing some basics in SR power converters, a hierarchy of control mechanisms is presented, together with their respective theoretical backgrounds and practical limitations. The respective controllers are then presented in a simulation context. The control scheme fully exploits the capabilities of high-frequency power converters and facilitates the extraction of currents at a unity power factor from the supply side, even under transient conditions. The control scheme takes into account losses and inaccuracies in the control electronics without deteriorating the intended waveforms. Through computer simulation, it has been shown that, in particular, the input current wave-shapes are greatly improved compared to the best-available operating data     

Thermomechanical properties of the coil of the superconducting magnets for the Large Hadron Collider

The correct definition and measurement of the thermomechanical properties of the superconducting cable used in high-field magnets is crucial to study and model the behavior of the magnet coil from assembly to the operational conditions. In this paper, the authors analyze the superconducting coil of the main dipoles for the Large Hadron Collider. They describe an experimental setup for measuring the elastic modulus at room and at liquid nitrogen temperature and for evaluating the thermal contraction coefficient. The coils exhibit strong nonlinear stress-strain behavior characterized by hysteresis phenomena, which decreases from warm to cold temperature, and a thermal contraction coefficient, which depends on the stress applied to the cable during cooldown.     

Electrothermal simulation of multichip-modules with novel transient thermal model and time-dependent boundary conditions

The ability of monitoring the chip temperatures of power semiconductor modules at all times under various realistic working conditions is the basis for investigating the limits of the maximum permissible load. A novel transient thermal model for the fast calculation of temperature fields and hot spot temperature evolution presented recently is extended to include time-dependent boundary conditions for variations of ambient temperature and surface heat flows. For this a Green's function representation of the temperature field is used. Also, general initial temperature conditions are included. The method is exemplified by application to a dc/ac converter module for automotive hybrid drives. The thermal model, which can be represented by a thermal equivalent circuit, then is combined with an electrical PSpice-metal-oxide semiconductor field-effect transistor (MOSFET) model to allow for the fully self-consistent electrothermal circuit simulation of 42-V/14-V dc/dc-converter modules. 670 converter periods with altogether 8000MOSFET switching cycles in the six-chip module can be simulated within 1-h computing time on a Pentium PC. Various simulation results are presented, which demonstrate the feasibility of the simulation method and allow for the optimization of converter losses. Short circuit modes of converter operation are investigated with a high temperature increase also revealing the thermal interaction between different chips.     

Design and performance evaluation of a compact thermosyphon

Thermosyphons are a promising option for cooling of high heat dissipating electronics. In this paper, the first known implementation of a compact two-phase thermosyphon for cooling of a microprocessor in a commercial desktop computer is presented. The implemented thermosyphon involves four components in a loop: an evaporator with a boiling enhancement structure, a rising tube, a condenser and a falling tube. The performance of the thermosyphon with water and PF5060 as working fluids, and the effect of inclination are studied experimentally under laboratory conditions. Experimental observations are also made at actual operating conditions to monitor the thermal behavior with changes in power output of the microprocessor. The inside cabinet of the desktop computer is also numerically simulated to understand the airside performance of the condenser.     

Electro-thermal analysis and optimization of edge termination of power diode supported by 2D numerical modeling and simulation

High reliability and performance of power semiconductor devices depend on an optimized design based on a good understanding of their electro-thermal behavior and of the influence of parasitic components on their operation. This leads to the need for electro-thermal 2/3-D numerical modeling and simulation in power electronics as an efficient tool for analysis and optimization of device structure design and identification of critical regions. In this paper we present an analysis and geometry optimization of a high power pin diode structure supported by advanced 2-D mixed mode electro-thermal device and circuit simulation. Lowering of the operation temperature by better power management and heat dissipation due to an optimized structure design will allow withstanding higher current pulses and suppressing the damage of the analyzed structure by thermal breakdown.     

Electro thermal modeling of the power diode using Pspice

In this paper, an improved electro thermal model of power diode was developed. The main local physical effects were taken into consideration. The suggested model is able to address the electrical and thermal effects. The model was confirmed through a comparison with other models having close characteristics for different circuits (AC-DC converter, turn-on and turn-off) and different temperatures. The diode was implemented in the Pspice circuit simulation platform using Pspice standard components and analog behavior modeling (ABM) blocks. The diode switching performance was investigated under influence of different circuit elements (such as stray inductance, gate resistance and temperature) in order to study and estimate the on-state and switching losses pre-requisite for the design of various converter and inverter topologies. The comparison shows that these models are simple, tunable with the electric circuit software simulator. They are more capable of predicting the main circuit parameters needed for power electronic design. The transient thermal responses were demonstrated for the single pulse and repeat modes. The achieved results show that our model is suitable for full electro thermal simulations of power electronic circuits.     

Low-Loss High-Peak-Power Microstrip Circulators

Smalll-signal magnetic losses due to coupling of the microwave signal to the spinwave manifold in a ferrite circuit under perpendicular pumping may be suppressed by biasing it between the subsidiary and main resonances. This paper describes the realization of two microstrip circulators biased in such a way. These magnetic conditions also coincide with those required to suppress spinwave instability at large-signal level. A device, using a triangular resonator, exhibited no nonlinear loss up to 1500-W peak at which power level thermal breakdown of the circuit metalization occurred both at the impedance step of the quarter-wave transformer and at the apex of the triangular resonator. A similar device using a disk resonator exhibited no nonlinear loss up to 2200-W peak at which power level breakdown of the circuit metalization again took place. A circulator using a disk resonator with a similar material but biased at magnetic saturation displayed nonlinear loss at 80-W peak.     

电力电子磁技术多维度教学方法探索实践

随着我国新工科战略趋势时代的开启,探索新的工程教育的中国模式已成为迫在眉睫的使命。本文根据电力电子技术跨学科的特点,从物理基础、开关频率及开关瞬态的关系等多维度对现有“电力电子”课程磁元件教学方法进行探索与实践。其特点是不拘泥于单一测试数据以及理论课程既定结论,而是进行多角度对比、多途径交叉验证的综合性观察,以培养学生在工程实践中面对复杂问题时的新工科思维能力。     

A lumped winding model for use in transformer models for circuitsimulation

A lumped circuit model is derived for a winding in a multiwinding transformer. The model is intended to be used in transformer models for circuit simulation using electrical-network simulators. A hybrid (partly electrical, partly magnetic) modeling approach is adopted in which magnetic components are described using the capacitance-permeance analogy instead of the widespread resistance-reluctance analogy. The network correctly models energy storage and power dissipation due to DC series wire resistance and to eddy current losses, independent of the way of excitation of the winding (electrical and/or magnetic). All component values are frequency independent and are parameterized by geometrical parameters, winding data and material parameters. The mathematical continued-fraction approximation technique is applied to derive approximating circuits to model eddy current losses. A fourth-order circuit shows acceptably small errors up to a frequency of about a factor of 1500 above the frequency at which eddy-current losses become apparent. The model is applied in a six-layer two-winding transformer model. Calculations both in the frequency domain and in the time domain show good agreement with measurements     

Evaluation of Thermal Resistance Matrix Method for an Embedded Power Electronic Module

Thermal characterization provides data on the thermal performance of electronic components under given cooling conditions. The most common thermal characterization parameter used to characterize the behavior of electronic components is the thermal resistance. In this work, experiments are conducted to obtain thermal characterization data for different chips in a multichip package. Using this data, it is shown that the assumption of a linear temperature rise with input power is valid within the expected range of operation of the electronic module. Secondly, the applicability of a resistance matrix superposition methodology to the packaging structure of an integrated power electronic module is evaluated. The temperatures and the associated uncertainties involved in using the resistance matrix superposition method are compared to those obtained directly by powering all chips. It is shown that for any arbitrary power losses from the chips, the resistance matrix superposition method can predict the temperatures of a multichip package with reasonable accuracy for temperature rise up to 50degC.     

Avalanche behavior of power MOSFETs under different temperature conditions

The ability of high-voltage power MOSFETs to withstand avalanche events under different temperature conditions are studied by experiment and two-dimensional device simulation.The experiment is performed to investigate dynamic avalanche failure behavior of the domestic power MOSFETs which can occur at the rated maximum operation temperature range(-55 to 150℃).An advanced ISE TCAD two-dimensional mixed mode simulator with thermodynamic non-isothermal model is used to analyze the avalanche failure mechanism.The unclamped inductive switching measurement and simulation results show that the parasitic components and thermal effect inside the device will lead to the deterioration of the avalanche reliability of power MOSFETs with increasing temperature.The main failure mechanism is related to the parasitic bipolar transistor activity during the occurrence of the avalanche behavior.