半桥式晶闸管弧焊逆变器变换电路原理分析

Principle Analysis of Commutating Circuit of Half-bridge Thyristor Arc Welding Inverter

通过对半桥式晶闸管弧焊逆变器变换电路工作波形的深入分析，提出了ＲＬＣＵ型电容放电等效电路，建立了电压、电流均为非零初始条件的二阶线性非齐次微分方程，得到了与实测波形完全一致的解。对电流波形的前沿、后沿，提出了在恒磁条件下的电流转移过程理论，得出了两个相应的等效电路。还讨论了电流脉冲后沿期间换流电容反压的形成及其变化规律。从而全面、正确地把握了这种电路的工作原理，为晶闸管弧焊逆变器的工程设计找到了正确的依据。

Through analysing the commutating circuit work waves of half-bridge thyristor arc welding inverter,a RLCU-type equivalent circuit of capacitor discharge is put forward. With the nonzero initial condition of current and voltage, the second order linear ordinary nonhomogeneuos differential equation of capacitor voltage is built up,and its solution completelly according with the praactically measured waves is derived. With front and back edges of the current pulse, the theory of current shifting process in constent magnetical condition is introduced, and two equivalent circuits corresponding to both of the edges are delivered. Inverse voltage forming of the capacitor and its varying rulse in the current back edge period are discussed. Thereby the work principle of this commutating circuit is understood clearly, and an overall and correct foundation for engineering design of the inverter is found.