ABSTRACT
For many years, induction motors have been preferred for a variety of industrial applications because of their robust and rugged construction. Until a few years ago, the induction motor could either be plugged directly into the grid (uncontrolled) or controlled by means of the well-known scalar volts per Hertz (V/f) method. In variable speed drives, both methods have serious drawbacks in the areas of efficiency, reliability, and electromagnetic interference (EMI). With the uncontrolled method, even a simple change in the reference speed is not possible. Additionally, its system integration depends highly on the motor design (i.e., starting torque vs. maximum torque, torque vs. inertia, number of pole pairs, etc).
