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

Abstract

Electrical steel laminations used in the transformer cores and motors are subject to stresses (σ) introduced during their construction. The magnetostriction as a major source of acoustic noise of the transformer cores has high stress sensitivity and is harmful to the electrical power grid. The higher harmonics of magnetostriction are more important than the fundamental when considering transformer noise. In the past, researchers have mostly focused on the magnetostriction of electrical steel under purely sinusoidal flux density. However, there are some higher harmonics of the voltage in the grid due to nonlinear load, which will induce harmonics in the flux density. It is useful find the relationship between harmonics in flux density and magnetostriction. The influence of harmonics in the magnetic field under zero stress has been studied.[1] The increase of magnetostriction with the percentage of harmonics in the flux density has been found, where the phase of harmonics with respect to the fundamental is the same.[2] The influence of harmonics with a variety of percentage and phase delays in the magnetizing voltage under stress on magnetostricon harmonics, where the amplitude of the flux density keeps constant, has rarely been studied. Moreover, there are few studies about the influence of harmonics in magnetizing voltage on the DC component in the magnetostriction.