In electrical engineering, three-phase electric power systems have at least three conductors carrying voltage waveforms that are offset in time by 120°. It is possible to measure the power in a three phase system using two transducers when there is no neutral, or three transducers when there is neutral.Blondem's Thorem states that the number of measurement instrument is one less than the number of current carrying conductors.A three phase system may be arranged in ∆ or Y. A "Y" system allows the use of two voltages from all three phases, such as 230Y400v system which provides 230v between the center hub and any one of the phases, and 400v across any two phases. A ∆ arrangement does not provide full capacity in dual voltage, however it has a greater redundancy as it may continue to operate normally with one of the three transformers offline, albeit at 57.7% of total capacityHarmonic currents in the neutral may become very large if non-linear loads are connected.
Read more about Three-phase: Definitions, Balanced Loads, Unbalanced Systems, Revolving Magnetic Field, Conversion To Other Phase Systems