Summary This paper presents a new analytical technique for modelling the impact of static eccentricity (SE), dynamic eccentricity (DE), and mixed eccentricity (ME) faults on electromotive force (EMF) or Back‐EMF, output voltages and currents of surface‐mounted permanent‐magnet (SMPM) machines. This model is based on the combination of the complex relative permeance and the eccentricity relative air‐gap permeance. It presents explicit formulas for no‐load and on‐load, field distribution, magnetic flux, EMF/Back‐EMF, and output voltages and currents of SMPM for different types of eccentricity fault. Furthermore, a new eccentricity model is presented and applied, which can cover more eccentricity fault types; some of them have not been so far considered in the literatures. Analytical results are validated by time‐stepping finite element method results. The analytical and numerical results refer to the fact that the SE does not cause any new frequency component in the EMF/Back‐EMF and currents spectra. However, the same is true in the case of DE and ME faults where some frequency components appear in the EMF/Back‐EMF and currents spectra, not only around the fundamental harmonic but also around some other harmonics.

Purpose This paper aims to present an analytical method, which combines the complex permeance (CP) and the superposition concept, to predict the air-gap magnetic field distribution in surface-mounted permanent-magnet (SMPM) machines with eccentric air-gap. Design/methodology/approach The superposition concept is used twice; first, to predict the magnetic field distribution in slot-less machine with eccentric air-gap, the machine is divided into a number of sections. Then, for each section, an equivalent air-gap length is determined, and the magnetic field distribution is predicted as a concentric machine model. The air-gap field in the slot-less machine with eccentricity can be combined from these concentric models. Second, the superposition concept is used to find the CP under eccentricity fault. At this end, the original machine is divided into a number of sections which may be different from the one for slot-less magnetic field prediction, and for each section, the CP is obtained by equivalent air-gap length of that section. Finally, the air-gap magnetic field distribution is predicted by multiplying the slot-less magnetic field distribution and the obtained CP. Findings The radial and tangential components of the air-gap magnetic flux density are obtained using the proposed method analytically. The finite element analysis is used to validate the proposed method results, showing good agreements with the analytical results. Originality/value This paper addresses the eccentricity fault impact upon the air-gap magnetic field distribution of SMPM machines. This is done by a combined analysis of the complex permeance (CP) method and the superposition concept. This contrasts to previous studies which have instead focused on the subdomain method.

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