The Distribution of Transient Magnetic Field and Eddy Current Losses of Three-Phase Five-Legged Transformer Under DC Bias

Abstract

In order to calculate the distribution of transient magnetic field and eddy current losses in iron core of three-phase five-legged transformer under DC (direct current) bias, and to analyze local overheating problem, This paper puts forward the coupling model of transient electric circuit and magnetic circuit considering the core topology and nonlinearity of ferromagnetic materials. The distribution and variation of transient magnetic field and eddy current losses of three-phase five-legged transformer under different DC bias conditions are studied. The results show that the amplitudes of magnetic flux density in core legs are maximum while in side legs are minimum; the amplitudes of eddy current losses in yokes are maximum while in side legs are minimum when there is no DC bias. Under DC bias, the amplitudes of magnetic flux density and eddy current losses increase with DC nonlinearly. The amplitude of magnetic flux density in B phase core leg grows fastest while in yokes grow slowest; the amplitudes of eddy current losses in side legs grow fastest while in core legs grow slowest. The results provide a reference to analyze the vibration and local overheating of three-phase five-legged transformer under DC bias more accurately.