Magnetostriction of Electrical Steel and Its Relation to the No-Load Noise of Power Transformers

This paper analyzes the relationship between the experimentally determined magnetostriction of grain-oriented electrical steel (GOES) coils and the no-load noise of power transformers (PT). The main source of a PT's no-load noise is the magnetostrictive vibration of the magnetic core built with stacked GOES sheets. With an in-house measurement system, in which steel coils with a mass of up to 6000 kg is measured, differences in the GOES materials' magnetostriction were identified. In this paper, we analyze the flux dependent behavior and harmonic composition of the magnetostrictive properties of different steel coils. Based on the identified differences in the steel coils' magnetostriction, two experimental studies with PTs are provided showing exemplary results. The first study shows initial findings of the relationship between the magnetostriction of the deployed steel coils and the emitted no-load noise of model transformers. In a second study, the aforementioned investigations were extended with measurements of large power transformers. Both studies cover a correlation and performance analysis including comparisons of the noise-related GOES certificate value B8 (also known as B800 value).