Classic Field Orientation Schemes

As demonstrated in Chapter 3, the FOP defines conditions for optimal torque production and the decoupling of torque control from field control, both under steady-state and transient operating conditions of an induction motor. Orthogonality of the rotor current and flux vectors must be maintained at all times. This requirement is inherently satisfied in the steady state when the rotor settles down to such a speed that the developed torque matches the load torque. Under transient conditions, however, in order to meet the FOP conditions, special techniques are required to provide an algorithmic equivalent of the actual physical disposition between the stator and rotor fields of the emulated d.c. motor.