In order to study the effect of harmonics on the equivalent magnetic circuit length and joint area loss of transformer core

based on the laminate core model completely designed and fabricated according to the power transformer standard

the equivalent magnetic path length and the loss characteristics of the joint region of the core model under different harmonic excitation conditionsare experimentally studied.Studies show that the influence of harmonic order and harmonic phase on the magnetic path length of the iron core is not very large.When the magnetic hysteresis loop or magnetization curve of the iron core is analyzed and calculated under harmonic conditions

the geometric mean length of the iron core can be approximately selected as effective magnetic path length.Under the excitation of different harmonic orders and different harmonic phases

the change rule of specific total loss characteristic in the joint area of iron core is similar:when the magnetic flux density is less than 0.5 T

the loss in the joint area is approximately zero;when the magnetic flux density is higher than 1 T

the loss in the joint area appears a significant upward trend.The method used in this paper and the conclusions obtained have certain guiding significance for electromagnetic analysis and optimization design of transformer products.