为了实现电力机车小型化轻量化的发展要求，国内外专家考虑通过采用提高变压器的工作频率减小变压器整体的体积和质量。铁心作为高频变压器的关键部件，可以准确计算铁心损耗，对中高频变压器的设计和优化具有重要作用。针对高频变压器铁心通常是工作在方波或脉宽调制（PWM）波等非正弦激励下的特点，对传统Steinmetz损耗计算模型进行了优化改进，给出了考虑磁密的变化率及波形系数对损耗的影响的Steinmetz改进损耗模型。同时，为了提高损耗模型在不同特征频率下的通用性，进一步对损耗模型系数的非线性进行研究，给出了模型系数随频率变化的非线性函数。最后，利用有限元计算结果同实物测量结果进行比较，证明了所提损耗模型在方波激励下对纳米晶体铁心计算的准确性。

In order to realize the development requirements of miniaturization and lightweight of electric locomotives, the overall volume and weight of transformer are reduced by increasing the working frequency of transformer. As the key component of high-frequency transformer, the iron core can accurately calculate the core loss, which plays an important role in the design and optimization of medium and high-frequency transformer. Aiming at the characteristics of high-frequency transformer cores that usually work under non-sinusoidal excitation such as square wave or pulse width modulation (PWM) wave, the traditional Steinmetz loss calculation model is optimized and improved. The Steinmetz improved loss model considering the change rate of magnetic density and the influence of waveform coefficient on the loss is given. At the same time, in order to improve the generality of the loss model at different characteristic frequencies, the nonlinearity of the loss model coefficients is further studied, and the nonlinear relation function between the model coefficients and the frequency is given. Finally, the finite element calculation results are compared with the physical measurement results, which proves the accuracy of the loss model for the calculation of nanocrystalline core under square wave excitation.