In Fig. 9 is shown the speed response at 1 (pu) under step
torque application during the interval of the proposed control
scheme (with transient optimum flux recovery) in
comparison with the case without transient optimization
(with transient rated flux recovery) and the case without
efficiency improvement (rated flux). The Fig. 9 shows that
the overshot of speed response without efficiency
improvement is better (lower and shorter convergence). The
speed overshot of the proposed method with flux optimum
recovery in transient state is shorter and bigger than the case
of efficiency improvement without flux control in transient
state. The speed overshot with the optimum flux recovery in
transient state increases 40% approximately comparing to
that with rated flux transient operation, since has better
convergence. Due to the shorter convergence of a transient
duration, the proposed control system achieves more input
energy saving compared with the rated flux recovery.