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

    Active Member

    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.