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Eddy-current analysis and losses estimation are significant components in the optimized design of the tractive transformer. The conventional analytical method forces to linearize the nonlinear magnetic property and as an important quantity in the calculation, the permeability is only acquired dependent on the empirical method. Furthermore, the computational precision is often difficult to assure in losses estimation when distorted excitation originated from nonlinear magnetized relation in electrical steel is neglected. In our study, the eddy-current field problem is delicately solved by analytical deduction, in which the nonlinear constitutive relation toward media and the harmonic component in the excitation source are sufficiently considered. Compared with the accuracy of the traditional formula, the proposed model achieves better accuracy on eddy-current losses with finite-element analysis, especially when the operating condition is closed to magnetic saturation. [ABSTRACT FROM AUTHOR]

A new testing method (oscillating wave method) has been proposed as a solution to the problem of short maintenance time in the traction power supply system, which could complete tests of winding and insulation via one connection and improve the maintenance efficiency of the transformer. Through the method being proved highly sensitive to winding faults, the variation under different winding states, however, remains unclear. This article aims to analyze oscillating wave signatures in the occurrence of axial displacement (AD). First, the modeling method will be proposed that can simulate oscillating wave signatures in different winding states. Then, the time-domain feature and the new proposed frequency-domain feature are applied to analyze the fault extent and location of AD fault. The results show that this model accurately simulates oscillating wave signatures. Moreover, the time-domain feature [Euclidean distance (ED)] is closely related to fault extent. The combined use of the time-domain feature (ED) and the frequency-domain feature (W-Energy entropy in Z-Score) is effective in the identification of fault location. These features, therefore, can provide the reference for winding state evaluation. [ABSTRACT FROM AUTHOR]