A physical model of an SF6 circuit-breaker arc was developed to study the behaviour of the arc as zero current is reached and to analyse its interaction with the circuit. The role of turbulence, processed using the mixing length model adjusted with experimental results, is an essential factor in the extinction of the arc. The variations of post-arc current were calculated as a function of the rate of rise of recovery voltage (RRRV) and of the time lag before application of this transient voltage. The authors then linked their physical arc model to a circuit model. Calculation of the arc-circuit interaction showed that the disturbances brought about in the RRRV by the presence of the arc should be taken into account, since they modify the post-arc current and thus the interrupting capability of the circuit-breaker.
A CAD system for the analysis of power electronic circuits for EMC applications is being developed. The system is based on 3-dimensional finite-element electromagnetic field computations, with the source currents or voltages extracted either from measurements or from standard circuit analysis.The finite-element solver for this application is configured in terms of magnetic vector potential ( A J and modified electric scalar potential (VI), incorporating, unusually, the Coulomb gauge V.&=O.Comparisons of computed electromagnetic fields with measurements of fields emitted from a 600V, 300A IGBT switching circuit are reported. Agreement in magnetic field strength is fair (within SdBpAlm) at the low frequencies (lOkHz-2OkHz) considered for this paper.
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