An Online Method for Static Eccentricity Fault Detection in Axial Flux Machines

This paper investigates a novel online method for static eccentricity (SE) fault detection of single-stator-single-rotor axial flux permanent-magnet (AFPM) machines. The method allows for both estimating the SE factor and computing the minimum air-gap position. As direct flux measurements are expensive, the proposed method for fault detection is based on the measurement of the voltages of three search coils uniformly distributed in the air gap. Unlike the current spectrum-based fault detection methods on which the winding configuration has a considerable impact, the proposed method can be used for any type of AFPM machine independently on the winding layout. A simplified 2-D analytical approach is used. Moreover, a circuit-coupled 3-D finite-element method (FEM) was used to compute the induced voltages in the search coils and show the validity of the method through 20 eccentric scenarios. Moreover, an experimental setup was built to validate the analytical approach and to confirm the results achieved with the 3-D FEM. Several experimental measurements have been done. All measurements confirm the accuracy of the proposed method. It is also shown that the method yields accurate results under any load condition.