Safety, disponibility and continuity of industrial systems are major issue in maintenance. In the last decades, these points are the important axes in the field of research. In fact, in many industrial processes research has picked up a fervent place and a particular importance in the area of fault diagnosis of electrical machines, in fact, a fault prognosis has become almost indispensable. The need of a mathematical model of three-phase induction machine, suitable for the simulation of machines behaviour under fault conditions, has received considerable attention. The paper presents a new practical and more precise model for induction motors after introducing inter turn short circuits faults. The proposed model is based on coupled magnetic circuit theory, capable to take into account any electrical asymmetry conditions. To verify the exactitude and the effectiveness of the model, simulation results for induction machine under interturn short circuit fault are presented. In spite of its simplicity, the proposed model is able to provide useful indications for diagnostic purposes. Experimental study is presented at the end of the paper to show that the proposed model predicts the induction machine behavior with a good accuracy.

This paper aims to provide a comprehensive study of sliding mode controller (SMC) performance for closedloop voltage control of DC-DC three-cells buck converter based on hysteresis modulation (HM) where an adaptive feedforward technique is adopted. To fix the switching frequency, the approach is to incorporate a feedforward adaptive scheme which is effectively a variant of SM control. Further, the use of an adaptive feedforward control that makes the hysteresis band variable in the hysteresis modulator of the SM controller to restrict the switching frequency variation feeding parameters uncertainties and loads disturbance, in order to overcome the design constraints and to mitigate the undesired transient response. The results obtained under load change, input change and reference change clearly demonstrates a great dynamic response of the proposed technique, as well as provide stability in any operating conditions, the effectiveness is fast with a smooth tracking of the desired output voltage. Simulations studies in MATLAB/Simulink environment have been performed to verify the concept.

Safety, disponibility, and continuity of industrial systems are major concern topics in maintenance". A key entity in the production chain is the asynchronous machine. Because of its critical role in different areas of production, its maintenance and monitoring remains of undisputed importance. During its operating time, the machine may be subject to various malfunctions like stator or rotor defects, demonstrating the absolute need for its regular diagnosis. This work provides new elements about the diagnostic in case of combined faults between turn to turn short circuit fault and unbalanced supply voltage using current signature analysis. These faults features will be analyzed through frequency domain parameters, and component harmonics spectrum analysis. The study of this combined electrical defect will be able to clearly and definitively define the fault index specific to the short-circuit fault. Simulation and experimental results validate the hypothesis.

Higher efficiency and lower losses are widely considered as the best metrics to optimize, in a high-power converter performance context. To provide a solution to the ever-increase of high switching frequencies challenges, we must explore soft-switching technologies to resolve interface issues and reduce the switching losses. This manuscript describes a comparative analysis between the fixed-bandwidth (FBW) and the variable-bandwidth (VBW) of the hysteresis modulation (HM) based on the conventional sliding mode (CSM) strategy. The two adopted techniques are applied to a bidirectional multichannel DC-DC asynchronous Buck converter. The cells are parallel-connected and operating in continuous conduction mode (CCM). The objective is to have a system that is more stable, more efficient and able to cope with variations in input voltage, load and desired output voltage. That requires, first, to attenuate the non-linearity phenomenon of the conventional sliding mode by placing a hysteresis modulation. Then, after applying this technique, we confronted the dilemma of the variable switching frequency. Our hypothesis was to incorporate a variable bandwidth of the hysteresis modulation. The results obtained under parametric variation clearly show the areas where significant differences have been found between the two approaches. Likewise, they both share several key features. Simulation studies in the MATLAB ® / Simulink ™ environment are performed to analyze system performance and assess its robustness and stability.