Autori: G. A. Cividjian, Jan Klejch, Ovidiu Dan Andrei

Editorial: XVII-th Symposium on Physics of Switching Arc, Vol 1, 1, p.53-56, 2007.

Rezumat:

Last years, authors developed a four parameters arc model before current zero, considering a linear
dependency of the cooling power and of arc time constant on the module of arc current. The model was in enough good
agreement with the synthetic test data records during the last 8-10 microseconds before current zero, obtained in Praha
HPL and the new introduced parameters of switching devices was determined to fit better the experimental data.
To see the variation of parameters in larger time period, in the paper, the same experimental data are smoothing, using
the least-squares Chebyshev approximations of arc voltage and current variations on time, using polynomials
orthogonal on a finite set of points. For all the period the high degree polynomial was used (up to 13-th deg.) and for the
period before voltage maximum a 3-degree polynomial. Thus, the first and second derivatives of the voltage and current
could be easy calculated and the time dependencies of the arc parameters like time constant and cooling power have
been evaluated.
The analysis confirm the linear dependence of these thermal parameters on time and module of the arc current, at least during the voltage slump, and also reveal the tendency to constant values of these parameters during earlier period, when the arc voltage has a small variation.

Cuvinte cheie: Black-box arc model, oscillogram, Chebyshev approximation