400V

400V is a nominal electrical voltage value used to describe three-phase alternating current (AC) power systems. It denotes the voltage between any two of the three phase conductors (line-to-line). In many parts of the world, such networks provide a line-to-neutral voltage of about 230V, so appliances and devices may be designed to operate at 230V single-phase or 400V three-phase.

Standardization and naming conventions: The 400V figure is defined in international standards as the nominal line-to-line voltage for three-phase distribution, commonly paired with 230V line-to-neutral in Europe and elsewhere. This arrangement originated from earlier values such as 380V and has become widely adopted in modern IEC-based grids, with regional tolerances allowing deviations around the nominal value.

Electrical characteristics: A typical 400V three-phase system is often described as wye-connected, yielding 400V between any two phases and 230V from any phase to neutral. The frequency is commonly 50 Hz in many regions, though some countries operate at 60 Hz with corresponding voltage values. The actual grid voltage varies with loading, generation, and regulatory limits, but 400V is used as the standard reference for equipment ratings and electrical calculations.

Applications and equipment: Many industrial motors, transformers, power supplies, and other three-phase equipment are rated for 400V (often also specified as 400V/50Hz). Domestic and light commercial loads in these regions typically use 230V single-phase supplies derived from the same distribution network. Equipment may use different winding configurations (for example, delta versus star) to accommodate various voltage grades, and proper insulation and protective measures are essential due to the higher line-to-line voltages involved.

See also: three-phase power, line-to-neutral voltage, IEC 60038.