Microprocessor-Controlled AC-Servo Drives with Synchronous or Induction Motors: Which is Preferable?

With the recent advances of power transistors and microprocessors it has become possible to design high-dynamic-performance ac-servo drives free of moving contacts using synchronous or asynchronous motors. Both schemes have their particular strengths. A general control principle, based on field or rotor orientation, is described which has been realized with a state-of-the-art microcomputer, where all the signal processing, including modulation of the inverter, is performed by software. Extensive tests have been carried out with different motors to compare the characteristics of the various types of drives.