Magnetostriction of Silicon Steel Sheets Under Different Magnetization Conditions

The magnetostriction of electrical steel is one of the main sources causing deformation and vibration in rotational machine and transformer cores. The presence of dc bias or higher harmonics of magnetic field in the electrical apparatus cores makes the vibration and noise of cores more serious. Therefore, it is necessary to identify how different magnetization patterns contribute to the magnetostriction noise. This paper performs the measurement of magnetostrictive strain in non-oriented and grain-oriented electrical steel sheets under sinusoidal excitation, one with a dc bias and the other with a third harmonic component, respectively. An investigation of the effect of dc biased magnetic field on the magnetostrictive property is carried out. The influences of a third harmonic of magnetic field with a variety of amplitudes and phase delay on magnetostriction are studied and the acoustic noise level is calculated due to the presence of the second (100 Hz) and fourth (200 Hz) harmonics of magnetostrictive strain. The research results are important for evaluating the noise of electrical machine and transformer core effectively.