Frequency converters

In a frequency converter of the type including a plurality of three phase inverters which produce three phase alternating currents inherently containing higher harmonic components, and a three phase transformer means for synthesizing the outputs of said inverters to obtain three phase alternating current, the improvement wherein said inverters are current type inverters, and said three phase transformer means comprise a plurality of three phase primary windings respectively energized by the outputs of said inverters and a plurality of parallel connected secondary windings thereby reducing harmonic components of lower orders, one of said primary windings and one of said secondary windings having a turns ratio of 1:k.sqroot.3 while the other primary winding and the other secondary winding have a turns ratio of 1:k, where k represents the voltage ratio of said transformer means.