Motor Power Factor with Variable Speed Drive

Discussion in 'General Electronics Chat' started by SerenityNow, Aug 31, 2016.

  1. SerenityNow

    Thread Starter New Member

    Aug 30, 2016
    Hello All,

    I know something about pumps, but less about the motors which drive them and am looking for some help in this regard.
    The motor in question is a three phase two pole squirrel cage induction motor. I am trying to calculate the power output from the motor based on the supplied current and voltage. To perform this calculation one of the things I need to know is the power factor. The manufacturer has supplied various performance characteristics of the motor including a graph of power factor vs. percentage name plate load (load factor) which I can use. However, I believe the power factor data is specifically for a drive frequency of 60 Hz and, with this in mind, I have two questions please:
    1) Given that my motor is connected to a variable speed drive, is the plot of power factor vs. load factor for 60 Hz still valid at other frequencies? Or, to put it another way, is the power factor of a motor running at its name plate load constant with regards to frequency?
    2) If the answer to question #1 is 'No' is there a recognised method to correct the power factor curve to other frequencies or is it something which needs to be determined experimentally?

    Any words of wisdom would be greatly appreciated.