Amorphous alloy and oriented silicon steel are two kinds of soft magnetic materials commonly used in manufacturing distribution transformer iron core.Among them, amorphous alloy has the advantage of low loss density, but it also has the problems of low saturation flux density and large magnetostriction. Oriented silicon steel has the advantages of high saturation flux density and small magnetostriction, but its loss density is larger. The completely opposite magnetization characteristics of two kinds of soft magnetic materials lead to the distribution transformer iron core cannot take into account low loss and low vibration.The combination of amorphous alloy iron core and oriented silicon steel iron core can synthesize the advantages of the two materials. Specifically, the composite iron core can take advantage of the high saturation flux density of oriented silicon steel to prevent the supersaturation of amorphous alloy. The core loss is reduced by the advantage of low loss density of amorphous alloy. The vibration of iron core is reduced by the advantage of small magnetostriction of oriented silicon steel. Therefore, it is significance to design the structural parameters of the composite iron core and rationally allocate the proportion of amorphous alloy and oriented silicon steel to reduce the core loss and vibration of the distribution transformer iron core.
In the composite iron core, the amorphous alloy part adopts the planar woundiron core structure, and the oriented silicon steel part adopts the planar stack iron core structure. The exciting coil bypasses both iron coresto realize the simultaneous excitation. According to the structure form of composite iron core, considering the magnetization saturation characteristics of amorphous alloy and oriented silicon steel, the equivalent dual nonlinear magnetic circuit model is established, and the iterative calculation method of flux density distribution is proposed. On this basis, the free parameter scanning method is used to design structural parameters of composite iron core. Firstly, the value range of free parameters is set. Secondly, all candidate free parameter sets are determined by arrangement and combination, in which each group of free parameters represents a composite iron core structure scheme. Finally, the flux density distribution of composite iron core in each scheme is iteratively calculated, and based on the constraint that the flux density of oriented silicon steel iron core is higher than that of amorphous alloy iron core, the feasible structural design scheme setsare determined.
According to the proposed design method, a composite iron core is designed, and an experimental prototype is manufacture according to the design results. The calculated and measured results of flux density distribution of composite iron core are compared. The mean relative error of flux density of composite iron core is 1.747%, that of amorphous alloy ironcore is 3.129%, and that of oriented silicon steel iron core is 7.663%, which verifies the validity of the proposed method.In order to demonstrate the advantages of composite iron core in no-load loss, comparative analysis of no-load loss between composite iron core, pure amorphous alloy iron core and pure oriented silicon steel iron core are carried out.Among them, the no-load loss of pure amorphous alloy core is 29.064W, the pure silicon steel core is 109.810W, and the composite core is 35.327W. Compared with pure oriented silicon steel iron core, the no-load loss of composite iron core is reduced by 67.829%.In order to demonstrate the advantages of composite iron core in mechanical vibration, the comparative analysis of vibration displacement between composite iron core, pure amorphous alloy iron core and pure oriented silicon steel iron core are carried out. The vibration displacement of pure amorphous alloy iron core is the largest, with a peak value of 1.085μm. The composite iron core is the second, and the peak value is 0.785μm. The pure oriented silicon steel iron core is the smallest, and the peak value is only 0.019μm. Compared with pure amorphous alloy ironcore, the vibration displacement peak of composite iron core is reduced by 38.200%.
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