Characteristics of induction motor drives with torque maximization in field weakening region

This article presents the new results of the investigation of the characteristics of vector-controlled induction motor (IM) drives with the torque maximization at field weakening. Analytical expressions that are necessary for the optimal algorithm of field weakening have been derived. The systematic numerical studies of the dependence of relative torque increase (RTI) index on the stator current limit for motor and generator modes of IM are provided. Taking into account the saturation of the main flux and magnetic losses in the machine iron, the extended description of IM has been used. In order to maximize the torque, while considering current and voltage constraints, the genetic algorithm has been applied. The results allowed assessing opportunities to improve the characteristics of drives by torque optimization. It has been established that the mean value of the RTI-index is approximately equal to 30-50% in the motor mode and to 15-20% in the generator mode. A significant growth of torque enables forcing of the acceleration and braking in the high-speeds region.