This paper presents an analysis of effects of dynamic air-gap eccentricity on the performances of a 6/4 Switched Reluctance Machine (SRM) through finite element analysis (FEA) based on a FEMM package associated to MATLAB/SIMULINK package software. Among the various Time-Frequency methods used for detection of defects, the Time-Frequency Representation (TFR) is an appropriate tool to detect the mechanical failures through the torque analysis by allowing a better representation independent from the type of fault. Simulation results of healthy and faulty cases are discussed and illustrate the effectiveness of the proposed approach.
KeywordsEccentricity, FEA, SRM, Time-Frequency Representation, Wigner-Ville Distribution.
INTRODUCTIONIn a wide variety of industrial applications, an increasing demand exists to improve the reliability and availability of electrical systems. Popular examples include systems in aircraft, electric railway traction, power plant cooling or industrial production lines. A sudden failure of a system in these examples may lead to cost expensive downtime, damage to surrounding equipment or even danger to humans. Monitoring and failure detection improves the reliability and availability of an existing system. Since various failures degrade relatively slowly, there is potential for fault detection at an early stage. This avoids the sudden, total system failure that can have serious consequences.Electric machines are a key element in many electrical systems. Amongst all types of electric motors, switched reluctance drive is more fault tolerant than other drives, mostly because it can continue operating and produce torque with one or more of its phases not functioning. This is due in large part to the decoupling of the machine phases. This machine, however, is not fault free, and questions emerge as to diagnostic and detection methods. In the case of switched reluctance machine (SRM), the knowledge of the physical effects of eccentricities is not yet very complete. Among the researches, which studied SRM under dynamic eccentricity (DE) fault, we find in [21] a 6/4 SRM with dynamic eccentricity modeled and simulated using a coupled structural and electromagnetic 2D Finite Element Method (FEM).A 3D FEM approach is applied in [22] for describing the performance characteristics of a 6/4 SRM under dynamic rotor eccentricity. This approach is also employed to evaluate the performance of the motor (including flux density, flux linkages, terminal inductance and mutual inductance profile) under different rotor positions and under different varying degree of angular misalignment fault in [23]. In [24] the same approach is used and a new hybrid method of obtaining the degrees of freedom for radial air-gap length in SRM operation under normal and faulty conditions based on magnetostatic analysis is presented.[25] proposes a mathematical model for calculating forces in novel switched reluctance bearingless motor (SRBM) with a single layer winding in eccentricity conditions.A literature survey showed a la...