Magnetic and magneto-mechanical vibration properties of non-oriented electrical steel

Non-oriented electrical steel, 30ZH105, was purchased from Nippon Steel Corporation. The steel has been widely used in rotating motor, small transformer, and electro-mechanical equipment cores. Because the noise generated from the steel core usually imposes an environment issue, in this study, we focus on the magnetic and magneto-mechanical studies of the 30ZH105 steel. Saturation magnetization (4πM_S) and coercivity (H_C), were determined from the hysteresis loop with field (H_E) along the rolling direction. The complex permeability (μ = μ_R - iμ_I), under various excitation conditions, was measured as a function of frequency (f) from 5 to 300k Hz by using an impedance analyzer. Longitudinal or transverse DC magnetostiction (λ_|| or λ_⊥) was detected by a strain gauge, and by applying magnetic field (H), either longitudinally or transversely. In addition, we used the same gauge to record the AC (e.g. with the exciting frequency, f_d = 60 Hz) longitudinal magneto-strictive vibrations (λ_L) as a function of time (t), for the sample under different magnetization states (M/M_S), where M is magnetization and M_S is saturation magnetization. By taking the fast Fourier transformation (FFT) on the real-time AC magnetostriction signal, we could analyze the fundamental (f = f_d) and other higher harmonic (f = nf_d, where n is a positive integer) vibrations: un-weighted and A-weighted. While performing the AC magnetostriction measurements, a sensitive microphone was placed near the sample in order to record the audio-noise spectrum.