Identification of loss models from measurements of the magnetic properties of electrical steel sheets

Abstract

Numerical simulations of electrical machines require good knowledge of the magnetic properties of the materials they are made of. The magnetic cores of these machines are made of electrical steel sheets, the magnetic properties of which are nonlinear and hysteretic. Moreover, the behavior of the magnetic flux density and the magnetic field strength of such materials depends on the form of the supply.

In the Laboratory of Electromechanics, there are several projects which aim to model correctly the behavior of the electrical steel sheet (hysteresis, stress-dependency, losses, etc.) when used in electrical machines. For this purpose, numerical models are developed and built in an in-house finite element program package. However, knowledge of the material properties and the parameters of loss models are necessary and needs to be measured. This work is proposed to measure the magnetization curves and specific losses of an electrical steel sheet. The measurements were carried out using a device specially designed for this purpose and adequate programs for field control. The measurements were conducted under rotating and alternating magnetic fields at different fundamental frequencies and amplitudes. The results of the measurements consisted of a large amount of data that has been analyzed, processed and presented in an appropriate manner. Moreover, the parameters of the loss models were estimated from the measurements through identification procedures that have been written and constructed in MATLAB software. The conclusions of this work provide the basis for a better understanding of the parameters needed to improve loss models.