Fault diagnosis is gaining more attention for electric machines running critical loads, whose sudden breakdown can result in unpredictable revenue losses. Consequently the motor drive systems with fault diagnostic and prediction features are of great concern and are becoming almost indispensable. Among all kinds of common faults, quite a few have relationship with unequal air-gap. So far, work on detection of eccentricity related faults in synchronous and induction machines have been well documented. However, few are reported on faults resulting fiom axial non-uniform air-gap. This thesis investigates the performance of a three-phase induction machine with non-uniform static eccentricity along axial direction or inclined static eccentricity. A variant of Modified Winding Function Approach (MWFA) is applied to study this fault. The relationship between the number of rotor bars, poles and the existence of fault related current harmonics is discussed. It is shown that inclined eccentricity also demonstrates similar characteristics as circumferential non-uniform air-gap (Static Eccentricity or Dynamic Eccentricity). The case that demands special attention is inclined eccentricity symmetric to the mid-point of machine shaft, which cannot be detected directly from current spectrum. These results will be useful reference to the designers of online tools for machine condition monitoring. Finite Element results to verify the inductance values used in simulation are also presented. The analysis is supplemented by the stator current spectra obtained fkom simulated results for different load and fault conditions. Finally a four-pole, 45 rotor bar, 2 kW induction motor is used to validate the theoretical and simulation results experimentally.

No description available.

No description available.

published_or_final_version / Electrical Engineering / Doctoral / Doctor of Philosophy

Thesis--Ph. D., University of Hong Kong, 1982. / Also availalbe in microfilm.

Thesis (M.S.)--University of Wisconsin--Madison, 1984. / Typescript. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaf 82).

No description available.

No description available.

Thesis (M. Phil.)--University of Hong Kong, 1995. / Includes bibliographical references (leaf 109-115).

Abstract The proposed research of investigating the interaction between high-temperature superconductors and linear motors is introduced. Background on levitated transportation, high-temperature superconductor applications and supercon- ductor theory is given. An analytical model is developed for calculating thrust and levitation forces produced by 3-phase windings on a pair bulk high- temperature superconductors. Results produced by this model for a spacing of 1 pole-pitch and 1 2 pole-pitch are presented. In order to verify the analytical model a prototype system is built from a linear motor primary and vehicles containing 2 rows of superconductors. Two vehicles are built with different spacing between the rows of superconductors in order to investigate the ef- fect of their positioning, with respect to the pole-pitch, on the thrust forces produced. Measured forces on these two vehicles are then compared with pre- dicted values showing that the model predicts the forces with less than 5% error. Problems with the analytical model are also discussed. Finally it is con- cluded that the model developed provides insight to the relationship between high-temperature superconductors and travelling magnetic waves, and that a 1 pole-pitch separation between superconductors produces higher forces. Rec- ommendations for further development of the prototype system are also given.