noun
rotary converter
Technical term in electrical engineering for a rotating machine that converts AC to DC or vice versa.
この工場では、回転変流機を使って交流を直流に変換している。
In this factory, a rotary converter is used to convert AC to DC.
Compound of 回転 (rotation) + 変流 (current conversion) + 機 (machine). The exact historical derivation is uncertain, but the term is a straightforward technical coinage.