The conversion electronic equipments convert an alternative electrical source of power into DC voltage.
A TRU (Transformer Rectifier Unit) typically converts a three-phase 115Vac current (or 230Vac) into a direct 28Vdc current. It consists of a winded transformer, rectifying diodes and an exit output filter. This type of converter, usually not exceeding 10kW, is used to power up navigation equipment, in-flight entertainment systems or electrical back-up equipment.
An ATRU (Auto Transformer Rectifier Unit) typically converts a three-phase 115Vac(or 230Vac) into a direct 270Vdc (or 540Vdc) current. Unlike the TRU, the ATRU is not galvanically isolated, hence allowing it to reach higher power density levels. These converters are designed to reach powers of several dozens of kW. ATRUs are usually used to power variable frequency electronic converters, controlling actuators motors such as those of the A380 ETRAS (Electrical Thrust Reverser Actuation System), or the A350's cabin recirculation fans.