Online Determination of Air Gap Lengths in Induction Motors based on Inverse Techniques

摘要

The knowledge about the length of air gaps is a crucial issue in electrical machines to determine performance parameters - especially when noise is considered. The Air gap of an electrical machine does not remain constant during operation, since it is influenced for example by temperature, magnetic forces and centrifugal forces for machines with high rotational speed. These effects increase dramatically for machines where the air gap is small like it is the case for induction machines. The small air gap in induction machines and the limited space makes it difficult or even impossible to place sensors inside the machine. Thus for the determination of air gap lengths during machine operation a method is sought that can be applied without using sensors inside the machine. This paper introduces a method to tackle the issue as an inverse problem aiming to reconstruct the air gap length by means of voltage and current measurements outside the machine.