Technician

In any motor, the voltage available for linkage with the rotor is: Applied Voltage to the Stator - Stator Impedance Drop. Isn't it? At very low speeds, when the frequency is decreased, the applied voltage too is decreased to maintain a constant V/f Ratio. Under this condition, the entire applied voltage is drooped in the stator impedance (as the applied volatge itself is low and the stator impedance is fairly constant) and very little or no voltage is available for linkage with the rotor. To overcome this, the stator current is broken into two vector components, the active vector and the recative vector. And the reactive vector is supplied as booster so that the stator voltage drop is supplied extra by the VSD. As this method uses the vector mesurement to control the speed & torque, this is called Vector Control.