Balance transformers can usually eliminate the zero sequence current and suppress the negative sequence current. This paper develops a novel approach for balance transformers, which is different from the traditional one with two-phase or three-phase symmetrical windings. First, the basic principle and the connected scheme of the transformer are clarified. Second, this paper derives the relationship between the primary and the second windings from a mathematical model for the new approach. Third, the balance condition (i.e. the neutral current in the primary side is zero) and the decoupling condition of the two-phase system are also obtained. Finally, the correctness and feasibility of the new approach are verified by the experimental results of a 1-kVA model transformer. Compared to the traditional balance transformers, the new approach has better performance and can be applied to the two-phase or single power supply, such as the traction power supply in electric railway.

Balance transformers can usually eliminate the zero sequence current and suppress the negative sequence current. This paper develops a novel approach for balance transformers, which is different from the traditional one with two-phase or three-phase symmetrical windings. First, the basic principle and the connected scheme of the transformer are clarified. Second, this paper derives the relationship between the primary and the second windings from a mathematical model for the new approach. Third, the balance condition (i.e. the neutral current in the primary side is zero) and the decoupling condition of the two-phase system are also obtained. Finally, the correctness and feasibility of the new approach are verified by the experimental results of a 1-kVA model transformer. Compared to the traditional balance transformers, the new approach has better performance and can be applied to the two-phase or single power supply, such as the traction power supply in electric railway.