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The knowledge of current density distribution gives important information for the study of the electric arc in low-voltage circuit breakers. Available experimental approaches to investigate the electric arc behavior include electrical measurements, optical, and magnetic diagnostic techniques. However, noninvasive experimental methods able to obtain the electric arc current density cannot be found in the literature. This article presents a nonintrusive diagnostic technique able to reconstruct the 3-D electric arc current density from its magnetic field measurements by solving a magnetic inverse problem. This inverse problem is known to be ill-posed, and Tikhonov regularization is used together with the L-curve method. Zero-divergence condition on the current density and boundary conditions are incorporated into the formulation of the inverse problem with the help of Whitney elements. A magnetic field measurement system is developed based on a Hall-effect magnetic sensor array and a data acquisition board. The sensor array is composed of 64 mono-axial analog-bipolar sensors distributed in eight columns and eight rows. The maximum measurable magnetic field of the sensor is 9 mT. The data acquisition board consists of eight analog-to-digital converters with a maximum sampling rate of 200 kHz and a 16-bits resolution. Experimental tests are carried out using the proposed method in order to study the arc dynamics. The reconstructions are compared with those of an optical diagnostic technique based on a charge-coupled device (CCD) camera. [ABSTRACT FROM AUTHOR]

Power converter is critical but prone to be failure in switched reluctance motor (SRM) drives. The open- and short-circuit fault characteristics of freewheeling diode in asymmetric bridge power converter are analyzed in details. Based on logic judgment, four online fault diagnostic methods with digital phase current analysis of power converter are proposed in this paper. The fault features are extracted by analyzing the relationship between chopping signal and the current information from some special positions. The four fault diagnostic methods are carried out according to the current obtained by detecting dc bus current and the lower freewheeling bus current, the chopped bus current, the upper excitation bus current and lower freewheeling bus current, the lower excitation bus current, and dc bus current, respectively. Comparisons between the four diagnostic methods are conducted. Simulations and experiments on a 12/8 SRM validate the effectiveness of the proposed methods. [ABSTRACT FROM AUTHOR]

Current density distribution in electric arcs inside low-voltage circuit breakers (LVCBs) is a crucial parameter for us to understand the complex physical behavior during the arcing process. In this paper, we investigate the inverse problem of reconstructing the current density distribution in arcs by inverting the magnetic field. This paper is focused on the modeling and computational phase for the magnetic inverse problem when linear ferromagnetic regions are considered in the model. To address the ill-posedness of the inverse problem, the standard method of least-squares approximation by Tikhonov regularization is studied, complemented with the generalized cross-validation criterion for regularization parameter selection. Considering the inclusion of a ferromagnetic region, two regularization approaches have been analyzed for the formulation of the currents in splitters and their corresponding magnetic field contribution. Effects of several features on the performance of the regularized solution have been investigated, including the signal-to-noise ratio, the value of permeability of the splitters, and the measurement distance. The numerical tests show the direct accessibility for the 3-D current density distribution with the proposed scheme, providing the accuracy and robustness for the applicability to study the arc behavior in LVCBs. [ABSTRACT FROM AUTHOR]

This paper presents a systematic analysis of the influence of magnetic measurement modeling on the regularized solution of magnetostatic inverse problems. The focus is on the application of the inverse problem technique to current distribution reconstruction of arc plasmas inside low-voltage switching devices. The inverse problems modeled with both the ideal sensor assumption and non-ideal sensor modeling are studied, considering the geometry and active area of sensors. The Tikhonov regularization is adopted to address the ill posedness of the inverse problem. Sensor arrays with random variations in sensor directions and positions are compared with arrays using perfectly aligned setup. The numerical results reveal that for mono-axial planar sensor arrays the ideal sensor assumption could be used to simplify the modeling process with serious environmental noises. Better reconstruction can be obtained using the non-ideal sensor model when the sensor variations are large. [ABSTRACT FROM AUTHOR]