Saturable reactor-resistor pair is proposed as a part of snubber and it is applied to a hard commutation chopper. A basic hard commutation chopper is designed and scr turn off process and saturable reactor is modeled to simulate the hard commutation chopper. SCR turn off model is based on the recovered charge characteristics given in the data sheet and the empirical result. For modeling of the saturable reactor, λ-i curve is measured and then important parameters such as saturation current and nonsaturation inductance are calculated from it. State equations are derived for each mode of the chopper and they are solved by Runge-Kutta order 4 method. It is shown that there is an optimum resistance which minimizes the reverse voltage spike and reverse dv/dt. Peak reverse recovery current Irm is reduced and reapplied forward dv/dt is increased as resistance Rx is increased. Saturable reactor-resistor pair can be used to reduce SCR power loss and value of Cs and can be applied to high power thyristor devices.
