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The series six-fold “phase hopping” AC-AC frequency converter is an extension of the traditional AC converter. This converter can increase the output frequency to close to the power frequency rate, and has the advantages of no circulation and no dead zone. But like most of the frequency converters, there is the problem of large harmonic. In order to effectively eliminate the adverse effects of harmonics, this brief designs a harmonic suppression method according to the special properties of this low frequency converter. Firstly, Fourier analysis and calculation are carried out on the output voltage waveform of the load end of the frequency converter, and the relationship between the harmonic content and the trigger Angle of the thyristor is obtained. After calculation, the optimal combination of the trigger Angle of the series six-fold is deduced, and the simulation is carried out with MATLAB. Finally, an experimental platform is built and the experimental analysis is carried out. The experimental results show that the theory and simulation analysis are correct. [ABSTRACT FROM AUTHOR]

Harmonic magnetic fluxes in transformer's core and harmonic currents in grid‐side winding can be restrained via the inductive filtering technology, and running noise of the transformer is reduced at the source. The A‐weighted sound levels of the measuring points are measured under DC bias. The noise test results verify this theory. When the fully‐tuned filters matched with the new converter transformer are inputted and not inputted, the noise response curves of the measured points are compared. The fitting coefficients of the noise values at 1250 and 1600 Hz with the unbalance degrees of the trigger angle are obtained. [ABSTRACT FROM AUTHOR]