Study On Vector Magnetostrictive Properties Of Electrical Steel Sheet Based On Three-axial Strain Gauge Measurement

The stator core in the electrical machine is laminated by non-oriented electrical steel sheets, and the magnetostrictive effect of the electrical steel sheet will make the high-power motor core deforming and make the vibration and noise of motor more serious. Therefore, the accurate measurement and analysis of magnetostrictive property in the electrical steel sheet are the prerequisite and basis for studying vibration and noise of the motor core. In recent years, with continuous development of test technology, the magnetostrictive measurement and property study on electrical steel sheet have been carried out overseas, but the relevant research in China is still in the initial stage. In order to investigate the magnetostrictive property of electrical steel sheet, in this paper, the alternating and rotating magnetostriction measurement systems were developed based on a three-axial strain gauge measuring technology, and the magnetostrictive property of non-oriented electrical steel sheet under some typical magnetization conditions was measured and analyzed. The vector relationship between the magnetic flux density and the magnetostrictive strain was modeled and its validity was verified through a ring core sample magnetostriction test. Research results can provide reference to the analysis and inhibition of core vibration and noise caused by magnetostriction. Main contents are as follows:First of all, the hardware platform of magnetostrictive characteristic-testing system was built. The hardware platform consisted of magnetic field generating device, a triaxial strain gauge with a gauge length of 10 mm, BNC adapter, Ni PXIe-6368 data acquisition card, the strain bridge box and the strain amplifier, in which the magnetic field generation system was from an alternating magnetic field excitation device and a rotating magnetic excitation device in the laboratory.Secondly, the software design of the magnetostrictive characteristic testing system was completed and the accuracy of the measurement system was comparatively validated. The measurement software code was complied based on the virtual instrument LABVIEW platform and it includes data initialization module, data acquisition module, filter module, principal strain calculation module, and so on.Then, the magnetostrictive characteristic curve of the electrical steel under the alternating and the rotation magnetization was measured, and the influence of the magnetization condition on the magnetostrictive properties was discussed. Based on the developed measurement system, the three-axial strain curves under various elliptical magnetization trajectories with different axial ratios, inclination angles and magnetic flux density values were obtained, the principal strain magnitudes and directions were computed, and the vector relationship of principal strain and magnetic flux density under a magnetization cycle was developed. The results show that the magnetostrictive strain under the rotating field is significantly greater than that under the alternating field.Finally, the interpolation surfaces describing the relationship between the principal strain and magnetic flux density vector under different axial ratios were built. Taking a ring core sample experiment as an example, the magnetostrictive data on several typical positions were measured, and the measured results and interpolated ones were compared and analyzed. The validation of the vector relationship model was verified. The results can provide reference data to the joint simulation of magnetostrictive force field and the electromagnetic field.