The calculation of core losses in inductive components is difficult and has not yet been entirely solved. In particular, it is impossible to predict the influence of a dc premagnetization on the losses without extensive measurements. For this paper, different materials have been tested to gain information on how core losses are influenced by a premagnetization. Measurements on molypermalloy powder, silicon steel, nanocrystalline material and ferrite cores have been performed. The Steinmetz premagnetization graph (SPG) that shows the dependency of the Steinmetz parameters ( , and ) on premagnetization is introduced. This permits the calculation of core losses under dc bias conditions. Such graphs are given for different materials and different operating temperatures. In addition, a detailed description of the test system is given, as high accuracy is crucial.

Core Losses Under the DC Bias Condition Based on Steinmetz Parameters

In modern power electronic systems, voltages across inductors/transformers generally show rectangular shapes, as the voltage across an inductor/transformer can be positive, negative or zero. In the stage of zero applied voltage (constant flux) core losses are not necessarily zero. At the beginning of a period of constant flux, losses still occur in the material. This is due to relaxation processes. A physical explanation about magnetic relaxation is given and a new core loss modeling approach that takes such relaxation effects into consideration is introduced. The new loss model is called i2GSE and has been verified experimentally.

https://www.hpe.ee.ethz.ch/uploads/tx_ethpublications/05955126.pdf

Improved Core-Loss Calculation for Magnetic Components Employed in Power Electronic Systems

http://forc.ucdavis.edu/papers/pike2001a.pdf

An investigation of multi-domain hysteresis mechanisms using FORC diagrams

A selection of recent results illustrating the application of off-axis electron holography to the study of magnetic microstructure in closely-spaced nanoparticles and nanowires is reviewed. Examples are taken from the characterization of FeNi nanoparticle chains, Co nanoparticle rings, two-dimensional arrays of naturally occurring magnetite crystals in minerals, and single crystalline Co nanowires. Approaches that can be used to separate the magnetic signal of interest from the mean inner potential contribution to the measured holographic phase shift are described, and the spatial and phase resolution that can be achieved are discussed.

/pdf/off-axis-electron-holography-of-magnetic-nanowires-and-48qsjgj9po.pdf

Giorgio Bertotti

Papers

hysteresis in magnetism (electromagnetism)