Anli Lin

Magnetostriction and the Influence of Harmonics in Flux Density in Electrical Steel

Measurement of magnetostriction harmonics under stress is beneficial to clarify the relationship between magnetostriction and transformer noise. In this paper, a magntetostriction measuring system with small uncertainty is developed to measure the magnetostriction under a stress of ±20 MPa. The magnetostriction under sinusoidal and non-sinusoidal flux densities can be measured by digital waveform control. The components of magnetostriction harmonics and specific power loss at different percentages of the third harmonic in flux density and phase delay of the third harmonic with respect to the fundamental harmonic are investigated.

Magnetostriction and the influence of harmonics in magnetizing voltage in electrical steel

This study reports measurements using laser Doppler vibrometry of magnetostriction in electrical steel under magnetizing voltage harmonics. The magnetostriction harmonics is then analyzed using fast Fourier transform method. A direct relationship between flux density and magnetostriction is observed; wherein, higher flux density results to higher magnetostriction.

The measurement system for orientation angle of permanent magnets

The measurement system with rotation mechanism is designed and built to measure the orientation angle of permanent magnets. The system based on the measurement of magnetic moment with Helmholtz coils is applicable to the magnets with different shapes and sizes. The measurement uncertainty of the orientation angle is 0.23° (k=2). The two dimensional (2D) method is proposed to substitute for the three dimensional (3D) method to improve the measurement efficiency.

High stability electromagnet power for Gouy magnetic balance

For application in the magnetic field of Gouy magnetic balance, a dc-current source with ±200 V/50 A for magnetic system has been developed. Through designing a first-order negative feedback system with no static error, the stability of this customized constant current source at 42.86 A approached to 1.59×10-5/30 min which at present was satisfied with the requirement of the magnetic system.

Sweep rate dependence of coercivity in closed magnetic circuit

A hysteresisgraph has been set up to investigate the sweep rate dependence of coercivity on NdFeB magnets in closed magnetic circuit. The linear relationship between coercivity and logarithmic sweep rate has been found and the maximum difference of HC in the sweep rate is 1.1%. The fluctuation field and activation volume have been deduced, which is in agreement with results in open magnetic circuit. This study is helpful to understand the coercivity variation of NdFeB in closed magnetic circuit in industrial measurement.