Calculation of the Switching-On Overvoltages in a Series-Connected Thyristor String

The switching-on overvoltages in a thyristor string are analyzed using the concept of the thyristor string as a time-varying capacitance. The treatment is primarily from the point of view of a sequentially fired string, but it is of wider applicability. Exact solutions are obtained for a set of ideal loads, while the solutions for other loads and for other departures from ideal are treated as perturbations from the ideal solutions. Experimental confirmation is presented.