The field oriented control (FOC) of induction motor provide one of the most suitable and popular speed control technique presently used. The principle of field oriented control is based on the control of both the magnitude and the angle of each phase current and voltage. The control of torque is normally achieved by controlling the armature with constant field current. The Field weakening is employed to increase the speed beyond a base peed. The simplicity and flexibility of control of dc motors have made them suitable for variable speed drive applications. In the field oriented control, a d-q coordinates reference frame locked to the rotor flux vector is used to achieve decoupling between the motor flux and torque. They can be thus separately controlled by stator direct-axis current and quadrature-axis current respectively, like in a dc motor. In this paper, the principle, classification, and the most common of the field oriented control are presented. |
