Historical and predicted trends of industrial AC drives

Development of AC drives have been gaining momentum with the advancement of power devices, phase controlled thyristors, self-turn-off devices like GTO and GTR, high speed turn-off devices like IGBT, and so on. The microprocessor-based control technologies have enhanced their qualities. A variety of drive circuits have been used in industries from main drives to auxiliary machines. Generally, the history of main drives show the clear picture of technological trends. On the other hand, auxiliary machines cover a lot of systems and a great number of applications. This paper reviews the state-of-the art drive technologies, especially in main drives for industry, and discusses a possible drive system toward the late 1990s