Magnetic state balance technology of transformer based on magnetic field modulation strategy

Abstract

The transformer core is easy to saturate in the half cycle under the influence of the remanent magnetism (RM) and the bias magnetism (BM), then the excitation surge current (ESC) and the DC bias will be generated, causing the transformer excitation current (TEC) distort, leading the winding temperature rise and decreasing the transformer insulation. In this paper, one kind of magnetic balance modulation method for the transformer core is proposed. TEC distortion could be improved by adjusting the transformer magnetic field distribution. Firstly, the AC/DC/DC converter was designed and connected to the auxiliary winding according to the hybrid transformer topology. Second, the specific modulated signal for the magnetic field modulation (MFM) was generated and output through the AC/DC/DC. The modulated forward and reverse DC current or the stepped AC current would be injected into the transformer winding to achieve the balance of the transformer magnetic state. Finally, in order to verify the correctness of the design scheme, a 1 kVA/380 V/220 V/38 V transformer experiment platform was built. The results showed that this proposed MFM strategy could effectively solve the impact of the transformer ESC, DC bias and prolong the transformer service life, which provides a novel idea to solve the transformer fault.