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Induction Motors: Power Consumed vs Power Delivered

  1. Jan 31, 2013 #1

    The equation for power consumption of a three phase induction motor is given by the equation:

    P = sqrt(3)*V*I*(PF)

    Does this differ from the power that is delivered to the motor. For example, if a motor is running at 460 volts, 30 amps with a PF of 0.82, then the power consumption is

    P = sqrt(3)*460*30*.82 = 19.6 kW

    What is the corresponding power being delivered to the motor? is it the same value? Just want to know if the power being delivered to the motor is different than the power the motor actually consumes.

    Best regards,

  2. jcsd
  3. Feb 1, 2013 #2


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    Gold Member

    One basic question, how it would be possible, that power delivered wouldn't be consumed ?

    Equations you are writing here are describing power delivered = consumed (consumed in many ways - iron losses, copper losses, friction, ventilation, mechanical power output).

    There is one more thing: difference between power output (mechanical power on shaft) and power input (your equations). Maybe you are refering to this ?
  4. Feb 1, 2013 #3
    Hello Berg:

    Your OP - refers to "power consumed" and "Delivered to", these are the same thing and referring to the electrical circuit - a matter of perspective, from the sources perspective or from the motors perspective. It is the Mechanical Power (shaft) output of the motor that will not equal these values due to losses in the motor - both electrically and mechanically. The better the motor - the better the efficiency etc.
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