Modelling of Angular Behaviour of Core Loss in Grain-Oriented Laminations Using the Loss Separation Approach

An approach to model the anisotropic behaviour of core losses in grain-oriented laminations that are used in advanced electrical machines and transformers is proposed in this work. Core losses are usually split into static hysteresis loss, classical eddy current loss, and excess loss. The static hysteresis and excess loss components exhibit strongly anisotropic behaviours which at low frequencies may be modelled using the orientation distribution function (ODF) approach. However, the anisotropic behaviour of core losses at higher frequencies is rarely addressed. Therefore, this work aims to offer a method to model the anisotropy of these losses for a wide range of frequencies. This work proposes a modified approach that uses the ODF and the Kondorsky law to compute the core losses accurately in any direction for a wide range of frequencies so that the losses due to different magnetisation processes can be studied separately. The paper also highlights possible causes behind the anisotropic behaviour of the excess loss. The proposed approach is also compared with the original ODF description for modelling the loss behaviour along arbitrary directions. The computed loss-frequency behaviour at different induction levels agrees with measured ones along arbitrary directions. The proposed formulation can be used to estimate the losses of transformers and rotating machines as a function of magnetic field direction and frequency.