Research Of Vector Magnetostriction Property For Electrical Steel Sheets Under Alternating Magnetic Flux

The magnetostriction effect of the electrical steel sheet is referred as a phenomenon bywhich the volume or size of material changes with the increasing of the magnetization strengthunder applied magnetic field externally. Although the magnitude of the magnetostriction of theelectrical steel sheet is a few micronmeters per meter, which is far less than1500-2000micronmeters per meter of giant magnetostrictive material, the vibration and noise of the corecaused by magnetostrictive effect of the electrical steel sheet significantly increases with theincreasement of core size of super large-capacity motors and transformers. Based on animproved one-dimensional magnetostrictive measurement device, in this paper, vectormagnetostriction property for non-oriented electrical steel sheets under alternatingmagnetization was developed. The detailed research contents are as follows:First of all, base on the analysis of oversea vector magnetostrictive measurement system,an improved single sheet magnetostriction tester with laser vibrometers was developed tomeasure the vector magnetostriction property of non-oriented electrical steel. During theexperiment, in order to investigate the relationship between magnetostriction andmagnetization direction, the samples were made by cutting along different angles to the rollingdirection. And in order to study magnetostrictive anisotropy, the “three-axial optical sensor”method was used to detect the magnetostriction along three directions with certain angles, andthe magnitude and direction of the principal strain were computed based on the knowledge onplane strain. The relationship between the magnitude and the direction of the principal strainof magnetostriction and applied magnetic field was discussed.Secondly, a mathematical model describing the relationship between principal strainvector of magnetostriction and magnetic flux density was established based on the linearpiezomagnetic equation. And a2-D interpolated surface describing the relationship mentionedabove was achieved by using the measurement data. Utilizing MAGNET and MATLABsoftware, the vector mathematical model of principal strain was coupled indirectly into finiteelement simulation computation. By simulation computation and experimental test of themagnetostrictive phenomenon for a simple model, it was verified that the effectiveness of bothproposed vector mathematical model and finite element analysis method. Then, the proposed vector mathematical model of magnetostriction principal strain wasapplied to the magnetostriction simulation in the stator core of a three-phase permanentmagnet synchronous motor. The vector magnetostrictive distribution in permanent magnetmotor stator core was analyzed, and the deformation of the motor stator iron core wascalculated.Finally, the effect of the magnetic field including higher-order harmonics on themagnetostrictive behavior of electrical steel was analyzed based on experimental test. Bycontrolling the harmonic contents of the applied magnetic field, the magnetostriction ofelectrical steel sheet was measured under alternating magnetic field containing different orderharmonics. The effect of a third harmonic with a variety of amplitudes and phase delays onmagnetostriction was extensively studied.