400V three-phase alternating current, also known as three-phase current or three-phase alternating current, is an electrical power distribution system commonly used in industrial and commercial applications. It consists of three individual alternating current sources or phases that are offset in time by 120 degrees and thus ensure uniform power delivery.

The voltage of 400V refers to the voltage between two phases (also called phase voltage). The voltage between a phase and the neutral conductor (also known as phase voltage) is usually 230V.

Three-phase alternating current offers several advantages over single-phase alternating current, such as higher power density, better efficiency and more even load distribution across electrical devices. Therefore it is often used for larger electrical applications, such as motors, heaters or industrial machines.