Convertors are intended for single-phase AC voltage frequency 50, 60Hz conversion into smooth regulated rectified current and serves for underground metallic constructions protection against corrosion.

Base convertor element of all type constructions is cathode protection rectifier unit that provides convertor main output parameters. Each unit involves power section and control system.

By operation principles and fulfilled functions units are divided into transformer type thyristor rectifiers (UKZV, UKZN, V-OPEC) and inverter type modular transistor rectifiers with conversion at high frequency (V-OPEK-I).