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Homework Help: Three phase induction motors

  1. Jun 1, 2008 #1
    hey does anyone know the effiency and power factor of a typical three phase induction motor?

    Last edited: Jun 1, 2008
  2. jcsd
  3. Jun 1, 2008 #2
    Well, it's always a good thing to start off with the definitions of efficiency, power, and power factor.

    Let [tex]\eta[/tex] be the efficiency, then [tex]\eta = \frac{P_{out}}{P_{in}}[/tex]
    Let P= power, then P=VI.

    Therefore the average Power = [tex]VIcos(\theta) [/tex]
    By definition of power factor, it is the ratio of average power/VI.
    Thus, the definition of power factor = [tex]\frac{VIcos(\theta)}{VI}=cos(\theta)[/tex]

    From here, use the Pythagorean theorem to solve for power factor of a three phase
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