The systematic analytical method is reqUired for the ac phase control circuit by means of an inverse parallel thyristor pair which has a series and parallel L-C resonant load, because the phase control action causes abnormal and interesting phenomena, such as an extreme increase of voltage and current, an unique increase and decrease of contained higher harmonics, and a wide variation of power factor, etc. In this paper, the program for the analysis of the thyristor phase control circuit with a series and parallel connected load of series R-L-C circuit units, is been developed. By means of the program, the transient and steady state characteristics of the circuit can be calculated and then comparative study of various versions of circuits can be carried out systematically. The usefulness of the program is demonstrated by some numerical calculated examples
