Intentionally unbalanced 3 phase building power?

Discussion in 'General Electronics Chat' started by nickw1881, Dec 30, 2009.

  1. nickw1881

    Thread Starter Member

    Dec 25, 2009
    I went to a job the other day and this company had an electric box with 3 phase, Y connected power input, where two of the output phases were 120V, and one was 220V. Is this common? I thought 3 phase loads were supposed to be balanced, though I suppose this one could be, as long as the power delivered was the same in all three transformer phases.
  2. zgozvrm


    Oct 24, 2009
    It sounds like you have a center-tapped delta, rather than a wye. With a center-tapped delta, you will have 220V when measured line-to-line (for all 3 possibilities: A-B, B-C, and C-A). But, line-to-ground or line-to-neutral measurements will give you 120 volts on 2 legs (typically A and C) and 208 volts on the third leg (typically B). This higher voltage leg is often called the "wild" or "crazy" leg.