Power Calculations in an Unbalanced 3 Phase Circuit

Discussion in 'General Electronics Chat' started by Houdini, Dec 13, 2007.

  1. Houdini

    Thread Starter Member

    Dec 13, 2007
    I have had some conflicting answers to how to measure and calculate the 3 phase power in an unbalanced circuit. Here is what I have.

    480 Volt 3 Phase Supply that is supplying a machine. I have measured the current in all 3 legs and need to calculate the power ( eg: the power that will spin the electrical meter). If it was balanced and all the currents were the same,, I could use "1.73 X v X I"

    I have read that you can use the 2 watt meter method (Measure the current and voltage on 2 of the phases and calculate the Power, then add them and that will be the Kw).

    I1 = 2.9 Amps
    I2 = 5.2 Amps
    I3 = 3.9 Amps

    What would be the way to calculate the power?:confused:

  2. recca02

    Senior Member

    Apr 2, 2007
    that would have helped if those were the line current and line voltages.
    if u measured current in each phase,just add all V*I for each phase to get apparent power i think that works for all balanced and unbalanced loads.
    for active power add I^2R of all phases.