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This paper addresses a simple and computationally efficient dynamic model for brushless permanent magnet (PM) motors under PM demagnetization faults. The impact of stator slots and spatial disposition of the windings are taken into account to improve the accuracy of a lumped-parameter $abc$ model. This model is suitable for tracking the dynamic behavior of fault components, as it can be accompanied by any control scheme and/or be used for model-based fault detection schemes. In addition, parameters of this model can be automatically tuned by an optimization process in the offline phase of the healthy machine. Finite-element simulations are carried out for proving the effectiveness of the proposed model. Verification is done in both time and frequency domains for four PM motors with different rotor and stator configurations. The simulation results are experimentally verified. [ABSTRACT FROM AUTHOR]

This paper presents a comprehensive analysis of permanent magnet synchronous machine stator winding impedance variation in inter-turn short-circuit and eccentricity faults. The phase impedances are monitored through an extended self-commissioning procedure at the standstill mode before or after operation, and hence are agnostic to well-known issues caused by transients, load/speed level, or controller coefficient dependency. Moreover, the effect of stator iron core saturation on the electrical parameters is analyzed in depth. In order to distinguish the inter-turn shorts from the eccentricity fault which exhibits similar behaviors, a classification algorithm based on the saturation effect is introduced and analyzed on the machines with different pole-slot combinations. Both two-dimensional finite element analysis simulation and experimental test results are provided to show the efficacy of this analysis. [ABSTRACT FROM PUBLISHER]

In this paper, magnet defect faults and their corresponding reflections on permanent-magnet (PM) motor stator variables are investigated. An analytical approach based on a partitioned magnetic equivalent circuit is developed to determine the influence of magnet defect faults on PM motor variables. Due to the flexibility of the proposed method, the effect of each rotor magnets on each stator coil can be calculated to obtain the induced back electromotove force under faulty cases and observe the fault-related signatures in the frequency spectrum. The proposed tool significantly reduces the computational burden and provides sufficient accuracy, which significantly eases to simulate several magnet fault scenarios and examine detailed topology dependence relations in shorter time. Different cases, including various numbers and locations of defected magnets, winding configurations, and crack direction effects, are studied to understand the magnet defect influences comprehensively. The experiments and simulations are carried out at different speeds and load conditions to fully characterize the fault signatures. Comparative 2-D finite-element simulations and experimental results justify the theoretical magnet defect fault analysis and show the efficacy of the proposed approach. [ABSTRACT FROM AUTHOR]

Nowadays, the armature transition is one of problems in railguns. Many kinds of mechanism were proposed by researchers to predict or explain armature transition phenomena. And many types of railgun were invented. In this paper, three types of railgun, including simple railgun, parallel-augmented railgun and muzzle-fed railgun, are investigated with numerical simulations. Since current density is the decisive factor to transition velocity, this study focuses on the current distribution in armature. The inductance gradient of railgun and magnetic field distribution are also investigated. In order to simplify simulations, rails and armature are considered in each simulation, and armatures of railgun are same. The Maxwell 3D modular of Ansoft corp. was utilized as the program code. The simple railgun is selected as the benchmark, and the other two types were compared with it. In the simulation of parallel-augmented railgun, two current sources (500kA, 60Hz) were connected to inner rails and outer rail independently. In muzzle-fed railgun simulation, the same current source as in simple railgun was connected to rails. Based on simulation results, conclusions are drawn that augmented railgun has the highest inductance gradient and the largest launcher efficiency. But the current density at rear part of armature is larger than that of simple railgun if the currents flowing through inner rails and outer rail are equal. The inductance gradient of muzzle-fed railgun is the smallest, but the current density at armature shoulder is the largest. Projectiles of muzzle-fed railgun will face the greatest magnetic flux density. [ABSTRACT FROM AUTHOR]