谐波激励下变压器铜屏蔽杂散损耗的计算和验证

通过参考IEC61378-2标准提供的换流变压器谐波损耗计算方法,得出计算变压器铜屏蔽杂散损耗的解析公式。基于P21~c-EM1简化模型,采用一种新的杂散损耗测量方法,即通过模型总损耗测量值减去模型激励线圈损耗的精确仿真值得到结构件中的损耗,以此作为实验值,对解析公式计算的结果进行验证。结果表明:铜板的基波损耗计算结果与实验值基本一致;基波叠加多次谐波激励下的铜板损耗与各次谐波单独激励下的铜板损耗之和大致相同;在激励电流频率相同的情况下,铜板杂散损耗与电流大小的平方满足一定的比例关系;在激励电流大小相同的情况下,铜板损耗与电流频率的0.8次方不满足IEC标准给出的频率特性。基于此,引入一个考虑磁场分布的修正因子对频率特性进行修正,通过修正结果与实验值的对比验证了修正因子的合理性。

Calculation and verification for stray loss of transformer copper shield under harmonic excitation

By referring to the harmonic loss calculation method of converter transformer provided by IEC61378-2 standard, an analytical formula for calculating stray loss of transformer copper shield is obtained. Based on the simplified model of P21c-EM1, a new method of stray loss measurement is adopted, in which the stray loss in the structure is obtained by subtracting the accurate simulation value of the model excitation coil loss from the total loss measurement value of the model. The obtained results are used as experimental values to verify the calculation result of the analytical formula. The results show that the calculative results of the fundamental wave loss of the copper plate are generally consistent with the experimental values. The copper plate loss under the fundamental wave superimposed multiple harmonic excitation is almost the same as the sum of the copper plate loss under each individual harmonic excitation. Under the same excitation current frequency, the stray loss of the copper plate satisfies a certain proportional relationship with the square of the current size. Under the same excitation current size, the relationship between the copper plate loss and the 0.8 times of the current frequency does not satisfy the frequency characteristic given by IEC standard. In these regards, a correction factor that considers the magnetic field distribution is introduced to correct the frequency characteristics. The effectiveness of the correction factor is verified by comparison results obtained from the correction approach and the experimental value.