Relationship between losses under a large flux excitation and small signal loss factors tanδ in magnetic cores for high frequency use

Abstract

AbstractFor the evaulation of magnetic core losses in a high‐frequency region, the small‐signal parameter tan δ or the relative loss coefficient tan δ/μs, which are a small‐signal parameter in the region of an initial permeability, has been used. The magnetic cores for transformers or reactors have recently been used at a frequency greater than 100 kHz, and with a magnetic flux density far greater than the initial permeability, due to the demands of miniaturizing switching power supplies. This paper examines the relationship between the large‐signal loss of magnetic cores and their tan δ in a frequency range of 1 kHz to 1 MHz. It was found that the large‐signal loss has poor correlations with a small‐signal parameter, such as tan δ or tan δ/μs. ‘A loss‐evaluation parameter’ ζ = tanδ/μs (1 + tan2δ) was newly introduced. It is shown that the large‐signal eddy‐current losses of most magnetic cores at a frequency greater than 100 kHz can be estimated with a high accuracy by using this parameter; ζ is expected to be a useful parameter for evaluating the losses of cores for power applications at a frequency greater than 100 kHz.