一种利用矫顽点微分磁化率定量评估取向电工钢片机械应力的新方法

A New Method for Quantitative Evaluation of Mechanical Stress of Oriented Electrical Steel Sheets Using the Differential Susceptibility at the Coercive Point

不同大小的应力会对取向电工钢片的磁化及损耗特性产生不同影响,定量评估取向电工钢片的应力大小对减小铁心损耗,提高电气设备的运行效率具有重要意义。该文提出一种利用磁滞回线在矫顽点的微分磁化率来检测电工钢片应力的新方法。首先基于扩展的磁力学磁滞模型推导出了矫顽点微分磁化率的倒数与应力的线性关系表达式,给出了一条可以用来定量评估应力的线性校准曲线。然后为验证理论公式的正确性和适应性,测量了两种不同型号的取向电工钢片在承受不同大小弹性拉应力和压应力时的矫顽点微分磁化率。实验结果与理论计算结果有很好的一致性,这为定量评估取向电工钢片的机械应力提供了一种简单实用的方法。

As a soft magnetic material with excellent electromagnetic properties,oriented electrical steel sheet is widely used in the manufacture of transformer cores.In the actual operation process,due to the bending effect inside the transformer and the overlaying of the silicon steel sheet,the iron core will be subjected to certain extrusion or tensile stress,and the magnetic characteristics of the silicon steel sheet under different stresses will be very different.Although tensile stress causes little change in magnetic properties,even a small compressive stress can cause serious deformation of the hysteresis loop and increase the hysteresis loss.Therefore,it is very important to determine the stress type of oriented silicon steel sheet and evaluate its magnitude to improve the operation efficiency of transformer.In this paper,a novel method for measuring the stress of electrical steel sheet is presented by using the differential susceptibility of the hysteresis loop at the coercive point.Firstly,based on the extended magnetomechanical magnetic hysteresis model and considering that the pinning coefficient of soft magnetic materials is approximately equal to the coercivity field,the linear expression of the relationship between the reciprocal of the differential magnetic susceptibility of the coercive point and the stress is derived,and the linear calibration curve is obtained.Then the hysteresis loops and magnetostrictive curves of B30P105 and 30QG120 silicon steel sheets under different stresses are measured by the BROCKHAUS-MPG200 soft magnetic material testing system.According to the hysteresis loops,the relationship between the differential magnetic susceptibility of the coercive point and the stress of the two silicon steel sheets is obtained.The magnetic susceptibility of the two kinds of silicon steel sheet increases with the increase of compressive stress and decreases with the increase of tensile stress,and the effect of compressive stress on the magnetic susceptibility of the coercive point is greater than that of tensile stress.Finally,according to the theoretical relation expression,the theoretical relation curves between the reciprocal of differential magnetic susceptibility and the stress of two kinds of silicon steel sheets are drawn.There is a good agreement between the theoretical curves and the experimental values of the two kinds of silicon steel sheets,which proves the correctness and universality of the theoretical derivation.Based on the extended magnetomechanical hysteresis model,a novel method for quantitative evaluation of mechanical stress of silicon steel sheet is presented.The reciprocal of the differential magnetic susceptibility of the coercive point varies linearly with the stress.By measuring the hysteresis loop of the silicon steel sheet,the stress of the silicon steel sheet can be calculated,which provides a linear calibration curve for stress detection.Different types,batches and manufacturers of silicon steel sheets will have different magnetostrictive characteristics,in other words,the slope of the calibration curve will also be different.However,in practical engineering applications,as long as the differential magnetic susceptibility of the coercive point is measured under zero stress and any two other stresses,the corresponding calibration curve can be drawn more accurately.This provides a convenient method for quantitative stress assessment of silicon steel sheet and a new idea for stress detection of other ferromagnetic materials.