With the possible exception of you, nobody here appears to be loading their spindles much. But these results from someone that does suggest that there is value in monitoring motor current anyway, especially at higher speeds and loads where other losses dominate. Since magnetization current is supposedly independent of load, subtracting the no load motor current at speed from the loaded current to estimate cutting torque should have value, especially at the higher loads when more of the spindle’s available torque is used. I think its a good idea to measure and log both motor currents and VFD input powers to weigh their relative merits.
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