A transformer rectifier unit (TRU) is a device that serves the functions of both a transformer and a rectifier. A transformer is a device that facilitates increasing or decreasing AC voltage rates while a rectifier is a device that converts AC current to DC current. TRUs are widely used in marine (saltwater) applications to prevent corrosion.
Transformer rectifier units (TRUs) operate by transferring electrical energy that originates in one circuit to another source via conductors that are inductively coupled. TRUs are used in a variety of industrial applications, most commonly aviation, engines and power generation.
TRUs protect metals that are submerged in soil or water from corrosion. In these environments a TRU impresses a DC current to the metal being protected in a direction that is inversely proportional to any current levels that would otherwise facilitate galvanic corrosion or other types of corrosion.