In this paper the occurrence of stator faults in line-start permanent magnet synchronous motors is analyzed. A dynamic model of the motor was developed in Matlab/Simulink, that considers the performance of the motor both in healthy conditions and under the occurrence of inter-turn short-circuit faults, at an early stage of development. To validate the presented approach, simulation results, covering the full range of operation and different fault severity levels, are compared with the motor experimental performance. The output of the proposed model, namely voltages and currents, present a good agreement with experimental results, demonstrating the accuracy of the proposed model. Additionally, an on-line fault diagnostic technique is explored, demonstrating its potentiality.

Two common defects in induction machines (IMs) are eccentricity and interturn faults, which should be diagnosed to prevent performance degradation and further damage. A popular fault-detection approach is the current signature analysis (CSA), because of its simplicity and nonintrusiveness. Under closed-loop control, it is combined with analogous voltage-reference (VR) signature analysis (VRSA). However, by using these methods in three-phase IMs, it is difficult to discriminate between these faults, which cause similar symptoms. Multiphase machines provide remarkable advantages such as inherent tolerance to open-phase faults. Six-phase IMs are particularly attractive since they allow adopting three-phase converters. Among them, those with symmetrical spatial arrangement of the stator phases offer superior fault tolerance. Nonetheless, the distinction between eccentricity and interturn failures in these IMs has not been addressed so far. This article studies the discrimination between eccentricity and interturn faults in symmetrical six-phase (S6) IMs by CSA or VRSA. It is shown that, conversely to three-phase IMs and most other multiphase IMs, in S6 ones, these two types of failures can be easily distinguished: interturn faults considerably alter the currents or VRs in the so-called $\boldsymbol{x}$ - $\boldsymbol{y}$ plane, whereas eccentricity leads to current/voltage symptoms only in the $\boldsymbol{\alpha} _{\mathbf{1}}$ - $\boldsymbol{\beta} _{\mathbf{1}}$ plane. Experimental results confirm the theory.

As one of the most important assets of the industry, it is crucial to fully characterise all failure modes showing potential to degrade the normal operation of induction motors (IMs). One of the failure modes which lacks detailed knowledge and proper diagnostic tools is the inter‐turn short‐circuit (SC) fault. Given the severity of such failure mode, it is pivotal to ensure that incipient fault symptoms are correctly identified, thus preventing critical damages to the IM. Unfortunately, the state‐of‐the‐art does not provide enough data to confirm whether the available diagnostic tools act out in due time to avoid permanent damage to the faulty IM. To evaluate the impacts of this failure mode in the temperature of the stator windings of an IM, this paper presents the results obtained from two alternative thermal models of the same IM, resorting to the lumped parameter thermal network method and to the finite elements method. The results confirm that diagnostic tools reported in the literature might not be effective, failing to correctly diagnose an inter‐turn SC fault and to warrant the lead time required to take actions suitable to prevent permanent damage to the IM.

This paper addresses the occurrence of stator faults in six-phase induction machines, with a symmetrical winding, operating under both balanced and unbalanced supply voltage conditions. A dynamic model of the motor was developed in Matlab/Simulink environment, taking into consideration the occurrence of inter-turn short circuit faults. To validate the proposed approach, simulation results, covering the full range of operation and different fault severity levels, are compared with the motor experimental performance. The voltages and currents obtained from the simulation present a good agreement with the corresponding experimental results, demonstrating the accuracy of the proposed model

This paper addresses the diagnostics of inter-turn short-circuit faults in the stator windings of symmetrical sixphase induction motors supplied by an unbalanced voltage three-phase system, or under the occurrence of a single-phasing condition. A new approach based on the analysis of the zerosequence component of the apparent power is proposed to diagnose the inter-turn short circuit faults, independently of the presence of unbalanced supply voltages or single-phasing conditions. Additionally, the voltage Park's vector modulus, and the analysis of the rms values of the six-phase motor currents are also considered in the proposed technique, to monitor and detect the existence of unbalanced supply voltage conditions and open-circuit faults, respectively. Experimental results prove the effectiveness of the proposed approach in discriminating between all these conditions.