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Electric motor efficiency calculation

  1. Nov 5, 2012 #1
    Hello everyone,

    I am trying to calculate the electric efficiency of some 3 phase electric motors but I am a little confused about the power factor.

    efficiency=work out/work in

    work out=rated W of my motor (hp*745.7)

    work in= V*A*PF*√3

    Is the work in correct?

  2. jcsd
  3. Nov 6, 2012 #2
    Your formula is for POWER. Work is Power * time. Balanced 3 phase P = V*A*PF*√3.

    Work = Energy = P*T ( You pay for Kilowatt Hours - not Kilowatts)

    However the trick in this type of project is typically accurately measuring the mechanical output - needing a calibrated dyno - or other device.

    Also - for efficiency it is important (or more meaningful) to define what the operating point is for the efficiency calculation / measurements. --e.g. A Cold motor is more efficient then a warm motor - etc.
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