<P> 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 / 400 V system which provides 230 V between the neutral (centre hub) and any one of the phases, and 400 V 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 . Harmonic current in the neutral may become very large if non-linear loads are connected . </P> <P> In a star (wye) connected topology, with rotation sequence L1 - L2 - L3, the time - varying instantaneous voltages can be calculated for each phase A, C, B respectively by: </P>

What is the neutral current in a 3 phase system