Control of Induction Motor Drives in the Field Weakening Region Fed by a Boost Converter

Induction motors are usually fed by voltage source inverters. In some cases, it is necessary to increase the speed of the motor beyond the rated speed. This could be done by increasing the supply voltage (which is not always possible) or by field weakening. Field weakening algorithms are desirable since the current and the voltage of the motor cannot exceed the rated values. However, the range of the controlled speed is limited because of the limitation of the input voltage of the inverter. In this project, considering the limitation of current and voltage, the fundamentals of the field weakening in induction motor are reviewed. Th motor performance is evaluated under a variable range of the input DC voltage. A three-phase boost converter is used to regulate the input DC voltage of the inverter. In fact, when the requested voltage of the control algorithm is greater than the producible voltage of the inverter, the input DC voltage of the inverter is increased by the boost converter. The performance of this drive is evaluated in terms of current, torque and speed of induction motor. Besides, the efficiency of the drive is discussed.