torque ratings of 3 phase 480 volt ac motors controlled by vector vfd ?
A vector or even a sensorless vector VFD should be capable of operating a motor from base speed right down to or very nearly to zero speed at 150% of rated torque as calculated from the nameplate speed and power ratings. The current required to produce 150% of rated torque should not exceed 150% of the motor nameplate current. The minimum speed at which the motor can produce rated torque continuously and the maximum time that rated torque can be maintained at stall depends on the specific motor design, particularly the cooling provisions. Motors equipped with a separately powered cooling fan can typically sustain rated torque at zero speed continuously. Manufacturers of VFD rated motors usually have rating curves that show the motor torque vs. speed continuous and intermittent capability.
