Some effects of core building on localised losses and flux distribution in a three-phase transformer core assembled from POWERCORE strip

Stacked three-phase model transformer cores were assembled from POWERCORE strip, and the localized flux and loss distributions were measured using arrays of search coils and thermistors, respectively. Staggering alternate layers of laminations caused localized changes of power loss of up to 36% in parts of the T-joints and corner joints. The localized changes can be related to the changes in in-plane flux distribution, particularly in overlap regions of the joints. Areas of high localized loss are also directly related to the presence of third-harmonic flux and rotational flux whose magnitudes are controlled by the core geometry