Effects of mixing materials on losses and cost of operation of three‐phase transformer cores

It has been previously shown that the building factor of three‐phase transformer cores can be improved by using materials with different permeabilities for limbs and yokes. This paper presents results of a comprehensive experimental study of the effect of using conventional, high‐permeability, and domain‐refined grain‐oriented 3% silicon iron in various parts of a small three‐phase, three‐limb stacked laminated transformer core. It is shown that the core building factor can be improved using certain mixtures of material and that the absolute core loss can be minimized only by using combinations of materials with suitable permeability and texture. The operating flux density and joint geometry are shown to be important factors in controlling the degree of improvement obtained. The results obtained from the models are used to predict the losses in a range of larger transformers and their costs of operation are compared by considering the capitalized cost of losses and the cost of the core materials. It is sh...