Mathematical formulation for modelling minor and major hysteresisloops of power ferrites

A mathematical formulation that would enable the Basso-Bertotti domain-wall-motion (DWM) model to describe those static hysteresis phenomena that are not necessarily governed by DWM is presented. The motivation for this work has been the need to characterise both the major loop and the minor loops of the power ferrites used in power electronic applications. The key contribution is the introduction of a model parameter m_t that defines the transition between low field/minor loops and high field/major loop. The formulation is verified against experimental data of a commercial manganese-zinc (MnZn) ferrite     

功率锰锌铁氧体材料的损耗分离

采用传统陶瓷工艺,制备了功率MnZn铁氧体材料。根据磁滞损耗、涡流损耗和剩余损耗与频率的关系,在Bm为50mT和200mT两种典型工作磁通密度下,对JPP—44、JPP—5两种典型低损耗MnZn铁氧体材料进行了损耗分离。结果表明:JPP—5材料的涡流损耗,最低可为JPP—44材料的1/10,而其磁滞损耗相当于甚至超过JPP—44材料,并深入分析了它们损耗组成不同的原因。     

Microwave Lithium Ferrites: An Overview

Lithium ferrites are discussed and compared with other spinel microwave ferrites and rare earth-iron garnets. Points of comparison are saturation magnetization, temperature performance, hysteresis loop properties, stress sensitivity, insertion loss, power handling capability, resonance linewidth, and cost. The main points of discussion deal with the relative effectiveness of lithium ferrites, nickel ferrites, magnesium ferrites, and garnets as elements employed in latching applications at frequencies in the S, C, X, and K/sub u/ bands. A section is devoted to the compositional modifications necessary for: 1) adjusting magnetization, spin-wave line width, coercive force, and magnetic anisotropy; 2) the minimization of stress sensitivity and dielectric loss; and 3) the improvement of microstructural characteristics.     

A dynamic equivalent circuit model for solid magnetic cores forhigh switching frequency operations

This paper presents a dynamic equivalent circuit model of solid magnetic cores for high frequency operations in power electronic circuits. The effects of eddy current, domain wall motion, and hysteresis are taken into account by distributed equivalent resistors and distributed nonideal differential inductors, respectively. The Preisach hysteresis model is employed to simulate hysteresis effects in the inductors. A discrete transform technique based on the transmission line method is adopted to develop a discrete model for numerical dynamic analysis. The resultant model is just a simple tridiagonal system of equations. Good agreement between computer simulations and measurements has confirmed the validity of the new model     

Electronic scanning by ferrite-loaded corner reflector antennas

The measured performances of the antennas which consist of a90degcorner reflector, a horn, a core wire of a coaxial line, two or three ferrite rods, and electromagnets magnetizing the respective ferrites are presented. The following are made clear for the antenna with two ferrite rods. The load of the ferrites yields the asymmetric power pattern owing to the anisotropy of the ferrites, though the antenna geometry and the magnetization of the ferrites are symmetric. Moreover, the remarkably sharper main lobe and the higher gain are obtained by loading the ferrites. The main lobe can be turned to the direction reflected about the symmetric plane of the antenna by reversing all the dc magnetic fields applied to the ferrites, that is, electronic lobe switching in theH-plane is realized. It is shown that the antenna loaded with three ferrite rods makes the continuous scan of the main lobe possible by applying the suitable magnetic fields to the ferrites. The direction of the main lobe of these antennas is turned by electronically changing the currents of the electromagnets, that is, by changing the tensor permeabilities of the ferrites. The reciprocity for antennas composed of isotropic media does not hold for these antennas. The receiving power pattern coincides with the transmitting pattern reflected about the symmetric plane when the same dc magnetic fields are applied for both cases. Hence, these antennas permit us to receive from a direction and simultaneously to transmit in the direction reflected about the symmetric plane.     

Comments on "Use of Ferrites for Absorption of Electromagnetic Waves"

It is shown that considerations of hysteresis losses in ferrites are not relevant to their performance as absorbers of radar signals.     

A SPICE model for near-field transient analysis of ferromagneticgrids

Ferromagnetic grids are becoming more and more popular for electromagnetic shielding applications in avionics, satellite design, and power electronic systems. This paper presents an equivalent homogeneous but anisotropic model of a planar ferromagnetic grid. The nonlinear characteristic and the hysteresis of the material are taken into account. The field source is a low frequency magnetic dipole placed in the proximity of the grid. Both grid and source models are given in the form of multiconductor transmission line (TL) equations. They are solved, in the time domain, by the circuit simulator SPICE     

Design of Composite Magnetic Circuits for Temperature Stabilization of Microwave Ferrite Devices

The magnetic flux density of unsaturated microwave ferrites can be made almost constant although microwave ferrite saturation magnetization, coercive force, and hysteresis loop shapes change substantially. Temperature stabilization of flux is achieved by a composite series magnetic circuit consisting of microwave, driver, and flux-limiter ferrites, and a control coil. The flux limiter constrains the circuit flux to an almost constant level throughout the operating temperature range, despite large changes in the size and shape of the microwave ferrite hysteresis loop. The driver ferrite supplies the MMF necessary to sustain the flux. Current impulses in the control coil energize and switch the circuit flux. Estimates of the required lengths and cross-sectional areas of the circuit elements, and of the required switching field and energy for a waveguide remanence phase shifter are given, along with the effects of leakage and fringing fluxes. Composite circuit techniques have been applied to an experimental remanence phase shifter. Unstabilized, a 16 percent loss of phase shift was incurred as a result of an 80/spl deg/C rise in temperature. By applying composite circuit techniques, this value was reduced to less than 2 1/2 percent for the same temperature range.     

馈能型直流电子负载数字化控制的研究

馈能型直流电子负载作为一种新型电力电子装置,较传统的负载相比,具有节能、体积小、重量轻等特点。本文简要介绍了基于DSP芯片TMS320F2812控制的馈能型直流电子负载系统的结构、原理,重点对基于有源钳位技术的直流变换部分,采用电流滞环控制的逆变部分,以及同步锁相环节的数字化控制进行了研究,并进行了仿真验证。     

钴掺杂量对锰锌铁氧体显微结构和性能的影响

采用氧化物工艺制备了钴掺杂的锰锌铁氧体。研究了钴掺杂量对其显微结构和磁性能的影响。结果表明,添加质量分数为0.02%的钴后,可以明显地改善材料的显微结构,使其磁滞常数(ηB)降低到1.5×10–7 mT–1,应用频率提高到200 kHz。     

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.     

Analysis of thermoelectric coolers by a spice-compatible equivalent-circuit model

The objective of this work was to develop a PSPICE-compatible equivalent circuit of a thermoelectric cooler (TEC). Equivalent circuits are convenient tools for power electronics engineers since they help in presenting a problem in electronic circuit terms and can assist in the design of power stages and the control circuitry and algorithms. A methodology is developed for extracting the parameters of the proposed model from manufacturers' data of TECs. The present model is compatible with PSPICE or other electronic circuit simulators. An important feature of the model is its ability to generate small-signal transfer functions that can be used to design feedback networks for temperature-control applications. Several examples of successful utilization of the model are presented. Data of many different manufacturers were examined and the model parameters were extracted. In all cases, the model was found to reproduce accurately the performance of commercial TECs. The accuracy of the model was also verified by experiments.     

二磨时间对MnZn铁氧体结构和磁性能的影响

采用氧化物陶瓷工艺制备MnZn功率铁氧体,研究二次球磨时间对MnZn功率铁氧体微观结构和磁性能的影响.通过对铁氧体断面微观形貌的表征及密度、电阻率和磁特性的测试,结果表明,随着二次球磨时间的延长,MnZn功率铁氧体的密度、起始磁导率、饱和磁感应强度及电阻率均先增大后减小,损耗则先减小后增大.当二次球磨时间为2 h时,密度、起始磁导率、饱和磁感应强度及电阻率均达到最大值,总损耗最小且在25～120 ℃宽温范围内均低于350 kW/m~3.     

Cobalt-Based Ferrites Characterization Using Two Different Terahertz Time-Domain Spectrometers

We report an experimental study of the electrical properties of manganese cobalt (MnCo) and nickel cobalt (NiCo) ferrites in the terahertz (THz) frequency band. The study is motivated by the potential of MnCo, NiCo, and other magnetic ceramics for the fabrication of active and passive devices for THz wave communications. Using two different terahertz (THz) time-domain spectroscopy systems, we characterized the optical constants of cobalt ferrites doped with manganese and nickel in the technologically important 0.2–1 THz frequency band. The MnCo and NiCo ferrites investigated in our study exhibit a lower refractive index and absorption coefficient in the 0.2–1 THz frequency band than commercial strontium ferrite. We observed that using different valency ion oxide leads to a sudden change of the refractive index as a function of sample stoichiometries. Our experimental results provide evidence that microwave ferrite technology can be extended to the THz frequency band.     

Disturbance-Observer-Based Hysteresis Compensation for Piezoelectric Actuators

We present a novel hysteresis compensation method for piezoelectric actuators. We consider the hysteresis nonlinearity of the actuator as a disturbance over a linear system. A disturbance observer (DOB) is then utilized to estimate and compensate for the hysteresis nonlinearity. In contrast to the existing inverse-model-based approach, the DOB-based hysteresis compensation does not rely on any particular hysteresis model, and therefore provides a simple and effective compensation mechanism. We design and fabricate a lead magnesium niobate-lead titanate (PMN-PT) piezoelectric actuator for microscale tip-based power sintering process. Experimental validation of the proposed hysteresis compensation is performed on the PMN-PT cantilever piezoelectric actuator. The experimental results demonstrate the effectiveness and efficiency of the approach.      

Millimeter-Wave Generation Experiment Utilizing Ferrites

It is estimated that at least 50 watts of peak power at 2-mm wavelength has been generated from 4-mm excitation by harmonic generation in ferrites. This experiment is similar to the frequency doubling previously reported from 9 to 18 kmc, except for some differences in optimum geometry and material. A wide range of ferrites has been used, as well as garnets and permanent magnet type materials. In carrying out this experiment it has been necessary to develop components such as a 4-mm high-power isolator, a calorimeter for measurement of the 4-mm and 2-mm power, and numerous 2-mm waveguide components.     

Simulation of magnetic component models in electric circuitsincluding dynamic thermal effects

It is essential in the simulation of power electronics applications to model magnetic components accurately. In addition to modeling the nonlinear hysteresis behavior, eddy currents and winding losses must be included to provide a realistic model. In practice the losses in magnetic components give rise to significant temperature increases which can lead to major changes in the component behavior. In this paper a model of magnetic components is presented which integrates a nonlinear model of hysteresis, electro-magnetic windings and thermal behavior in a single model for use in circuit simulation of power electronics systems. Measurements and simulations are presented which demonstrate the accuracy of the approach for the electrical, magnetic and thermal domains across a variety of operating conditions, including static thermal conditions and dynamic self heating     

Hysteresis of giant intensity fluctuations of emission for two-dimensional electrons in the conditions for the integer quantum Hall effect

On observation of giant intensity fluctuations for the emission of two-dimensional electrons in two-layer electronic systems in the conditions for the integer quantum Hall effect, a hysteresis is detected in the magnetic-field dependences of the amplitude in these fluctuations. It is shown that the hysteresis is observable only at a certain thickness for the barrier separating the electronic layers, and the thickness is such that the inter-layer spacing is comparable with the spacing between electrons in the two-dimensional plane. It is established that the amplitude for the hysteresis in a magnetic field depends on the temperature and on the difference between the concentrations of electrons in the layers. The observed phenomenon can suggest that, in coupled two-layer electronic systems in the conditions for the quantum Hall effect, a new coherent ordered state characterized by two critical temperatures is formed.     

低失真MnZn铁氧体中ZnO含量对磁特性的影响

为了提高非对称数字用户线(ADSL)接入系统的网络传输质量,采用传统氧化物陶瓷工艺制备了低失真MnZn铁氧体,并研究了在Fe2O3含量不变的前提下,ZnO含量与其磁特性的关系。结果表明:适量的ZnO可以提高起始磁导率μi,降低磁滞常数ηB。随着ZnO含量的增加,μi值先增大后减少,截止频率fr先减少后增加。当x(ZnO)为23%时,其μi=8 100,ηB=0.42×10–6/mT。     

Accelerated degradation data of SiC MOSFETs for lifetime and Remaining Useful Life assessment

The phenomenon of threshold voltage instability has been reported to be a critical issue for the first generation of commercial SiC MOSFETs. For aeronautic mission profile, the long term reliability of such device has to be estimated prior to any integration. As far as the author knows, this paper proposes one of the first attempts to use a non-homogeneous gamma process to model the threshold voltage degradation of a commercial SiC MOSFET. Such approach allows evaluating the time to failure as well as it distribution thanks to the proposed Acceleration degradation testing methodology. All the data collected during the ageing tests will be used to model an acceleration factor and to extrapolate the Time-To-Failure in a given application. Ultimately, the use of gamma process to evaluate the Remaining Useful Life of electronic component is described as a first step toward prognostic of Remaining Useful Life in embedded power electronics.