As the calculation of transformer no-load characteristics measured by low-frequency test method is not perfect, different interpolation methods are explored to fit and convert the transformer's volt-ampere characteristics under power frequency (50 Hz) excitation to find the best interpolation fitting conversion method. The no-load test of transformer is carried out by using 10 Hz, 15 Hz, 20 Hz low-frequency square wave and triangular wave excitation. Then the measured excitation voltage, excitation current and no-load loss are converted to those of 50 Hz sine wave excitation. The converted volt-ampere characteristic curve is calculated by the proposed algorithm, and compared with the measured results under the 50 Hz sine wave excitation. Experiments show that under the condition that the magnetic flux amplitudes are equal at each frequency of non-sinusoidal and sine waves, whether it is square wave or triangular wave excitation, the volt-ampere characteristic curve converted to the 50 Hz sine wave excitation by the proposed method can better approximate the curve of the measured 50 Hz sine wave excitation. The average values of the relative errors of the converted excitation current of the three frequencies are within 4%, and those of the converted excitation voltage of the square wave are within 1.1%, and those of the converted excitation voltage of the triangular wave are within 0.47%. Compared with the generalized Steinmetz equation method and the multi-frequency method, the proposed method has a better conversion effect and can almost replace the no-load test results of the 50 Hz sine wave, which has practical value in engineering.

由于用低频测试方法测得的变压器空载特性的计算并不理想，因此探索了不同的插值方法来拟合和转换在工频（50 Hz）激励下变压器的伏安特性，从而找到最佳的插值拟合转换方法。变压器的空载测试是通过使用10 Hz，15 Hz，20 Hz低频方波和三角波激励来进行的。然后将测得的励磁电压，励磁电流和空载损耗转换为50 Hz正弦波励磁。通过提出的算法计算出转换后的伏安特性曲线，并将其与在50 Hz正弦波激励下的测量结果进行比较。实验表明，在非正弦波和正弦波各频率的磁通量幅值相等的情况下，无论是方波激励还是三角波激励，伏安特性曲线都可以通过50Hz正弦波激励转换为50Hz正弦波。提出的方法可以更好地逼近被测50 Hz正弦波激励的曲线。三个频率的转换励磁电流的相对误差的平均值在4％以内，方波的转换励磁电压的相对误差在1.1％以内，三角波的转换励磁电压的相对误差在10％以内。 0.47％。与广义Steinmetz方程法和多频法相比，