Technologies and applications in open-loop PWM inverter drives

The application of AC motor drives is rapidly growing throughput the world. The introduction of vector control technology has greatly increased the rate of this growth and made possible the utilization of induction motor drives in many applications where it has previously been considered impossible. Even with this growth in the applications for vector control technology, several developments have been implemented in nonvector control drives to assure that their usage will also continue to expand. Included among these developments is a full range, adaptive torque boost function which is particularly effective at increasing the low speed torque in heavily loaded machines. Further, a new PWM technique which reduces the inverter´s low frequency output harmonics and the driven motor´s audible noise has been utilized. Finally, a control scheme which allows the restarting of a coasting motor has been implemented to improve the recovery from an input power interruption, instantaneous overload or other fault condition. These new techniques and their typical application are introduced in this paper.<>