The main aim of this paper is to identify relationships for direct determination in the time domain of periodic steady-state solutions for differential equations. A new discrete operator of differentiating has been defined. As a result, a set of algebraic equations has been written. Based on this, an algorithm for nonlinear differential equations has been proposed. Numerical tests have been carried out both for a new discrete operator and for steady-state analysis in a simple electromechanical converter.
This paper discusses the detection of internal faults in the stator and rotor windings of synchronous machines. Using current signature analysis, it is demonstrated how by using low cost equipment, it is possible to detect the fault by monitoring the currents. The process of detection is totally optimized, and the processing time is enough to identify the fault before the total machine damage. Using the spectrum of the healthy machine as a reference, the followed methodology allows the timely and reliable detection of faults.
The study of the interaction between faults of different natures is a crucial step for the development of effective systems for fault detection. The analysis of the electrical signals using the actual motor current signature analysis (MCSA) techniques may lead to different results and, as a consequence, an incorrect diagnosis of the fault due to the fact that the non-linear interactions between both faults are difficult to predict with high precision. The relationship between the electrical and mechanical components has been extensively studied in the past, but despite the progress made, the introduction of new control systems or the nonlinearities presented in the electrical machine, still makes it hard to diagnose faults. The study below attempts to show the evolution of the induction motor signatures when electrical and mechanical faults occur simultaneously. The Fourier analysis of the signatures presented in this paper indicates that the typical analysis carried out to diagnose the state of the electrical machine may be interpreted as an indicator of a different type of fault.
The article shows a new field of application for the matrix converter (MC) as the interconnecting device between the high speed, permanent magnet generator and the grid. The converter works under the developed control algorithm based on a so called ‘area based’ approach. The device consists of a converter, a transformer (or transformers) and filters and is supposed to substitute or revolution decreasing gear box or DC link based power electronic converter. Several structures, including multiphase structures (3, 12 phase) were investigated and their properties were assessed using the results of Matlab Simulink based simulations. The simulations were performed using the standard Simulink models and the developed, simplified permanent magnet motor model. The results were very satisfactory, i.e. input waveforms distortions, output current and machine torque ripples were at acceptable levels for the multiphase structures and high frequency input. The waveform distortions were found to be a function of input frequency and the number of phases in the conversion device, but the structure of the converter was limited to a 12x12 structure for economic reasons.
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