How do you modify a 3-phase electric range for a 4-phase outlet?

In electrical engineering, three-phase electric power systems have at least three conductors carrying alternating current voltages that are offset in time by one-third of the period. A three-phase system may be arranged in delta (?) or star (Y) (also denoted as wye in some areas). A wye system allows the use of two different voltages from all three phases, such as a 230/400V system which provides 230V between the neutral (centre hub) and any one of the phases, and 400V across any two phases.

A delta system arrangement only provides one voltage magnitude, however it has a greater redundancy as it may continue to operate normally with one of the three supply windings offline, albeit at 57.7% of total capacity. 1 Harmonic currents in the neutral may become very large if non-linear loads are connected. Generally, in electric power systems, the loads are distributed as evenly as is practical between the phases.

It is usual practice to discuss a balanced system first and then describe the effects of unbalanced systems as deviations from the elementary case. An important property of three-phase power is that the power available to a resistive load, , is constant at all times. Since we have eliminated we can see that the total power does not vary with time.

This is essential for keeping large generators and motors running smoothly. For the case of equal loads on each of three phases, no net current flows in the neutral. The neutral current is the inverted vector sum of the line currents.

See Kirchhoff's circuit laws.