Optimal Operating Point in Design of Transformer by Compensating the Effect of Tapchanger

In design of electrical machines, specific electrical and specific magnetic loadings are main parameters and there has to be a balance between them. When tapchangers are used in transformers, the balance between these two parameters is changed. In fact, use of tapchangers, leads to some variation of flux density. Hence, the specific magnetic loading (flux density) must be lower than the optimum value, to allow for the condition when it might be increased. When one tap is changed, number of turns and voltage of transformer winding will be changed and as a consequence, flux density will not remain constant. In this paper for further clarification, finite element analysis is carried out to verify this issue. The aim of this paper is to reduce the effect of tapchanger variations in flux density of transformers. Therefore, a new method is presented in this paper. This method employs a DC source embedded between unused turns in the winding of transformer in order to compensate the effect of tapchanger in flux density variations. This leads to compensation of the undesirable effect of tap changer. In addition, operating point returns back to its normal condition. The main feature of the proposed method is that it requires only an additional DC source plus a switch. Hence, performance of transformer is improved while not much expense is imposed.