Torque control requires a variable-frequency drive (VFD), and it differs from speed control because the primary goal is to operate the motor at a commanded torque, regardless of the resulting speed. VFDs operating in torque mode modulate the power and speed to achieve a commanded torque.
This article from our Endeavor Business Media partner site, Processing, explains why torque control is necessary for many types of winding/unwinding applications and how general-purpose sensorless vector VFDs can perform this function.
