Direct self control of inverter-fed induction machine, a basis for speed control without speed-measurement

The authors present one possible way of calculating the exact speed of an inverter-fed induction machine without mechanical devices. In addition, a simplified algorithm, applicable for drives that do not demand high dynamic speed control performance (e.g. fans and pumps), is described. The control scheme builds on the analog basic version of the direct self-control of an inverter-fed induction machine and only needs a few extra operation amplifiers for signal processing. The performance, including start-up of an already rotating drive, is documented.<>