Permeability and its Influence on the Broadband Frequency Response of a Power Transformer

This paper considers the effect of the complex permeability of a power transformer core for the full FRA test spectrum (typically less than 10 MHz). Current work in the area generally neglects the core beyond a few 100 kHz. This paper demonstrates that the relative complex permeability is significant at 1 MHz and above unity until frequencies beyond 15 MHz. The paper also demonstrates that for broadband small signal testing, such as FRA, the low field conditions induced by the injected signal result in a relative permeability that approaches the initial permeability of the core. This ensures that the relative permeability remains approximately constant over a large range of frequencies and will have a degree of independence with regards to the injection voltage source.