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Calculate Power Usage using device specs

  1. Feb 17, 2012 #1
    Hi there!

    I'm working on a project that involves the operation of a variable speed drive controlling a motor. I'm wondering if it is possible to calculate the power usage of the motor if the rpm of the motor is known. I'm not very knowledgeable when it comes to matters electrical but I thought it may be possible by calculating power use by making use of the motor specifications.

    Can anyone point me in the right direction?

    Thanks in advance

  2. jcsd
  3. Feb 18, 2012 #2
    You need to know the specs for the motor such as watt and volt-amps. RPM is not enough information. Horsepower will give a lower limit but not the maximum power.
  4. Feb 18, 2012 #3

    jim hardy

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    i think it depends on the mechanical load attached to the motor...

    a fan or pump load will demand different power vs rpm than an elevator would.
  5. Feb 22, 2012 #4
    Well the motor will have a disc rotating on a shaft so the load will be almost insignificant I think. I have the spec's of the motor so I had hoped to be able to "work backwards" using this info and calculate the power usage.
  6. Feb 22, 2012 #5
    "Well the motor will have a disc rotating on a shaft so the load will be almost insignificant"
    In that case the power consumption will be almost insignificant, just because a motor spec says 10KW at 1800 RPM doesn't mean that it will always use that 10 KW, the 10 KW is the maximum it is capable of.
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