Maximum torque control of induction machine in deep flux weakening region

In modern motor drive system, the maximum torque-speed range of the induction machine is limited by the allowable phase current and the DC bus voltage. When the induction machine speed increases, the machine eventually enters deep flux weakening region and the DC bus voltage becomes the only limitation to the torque production capability of the machine. The maximum torque in the deep flux weakening region can be achieved by supplying the optimal current to the stator windings. In this paper, the method to determine the optimal stator current is proposed. It is shown that the maximum torque is higher than the pull-out torque of the machine in deep flux weakening region.