Design, Simulation, Implementation and Control of Digital Self-Compensating Method for Integral Cycle Power Control for Welding Application

The Class of ac power controllers consists of Solid State Power Controller (SSPC) which connects and disconnects the load to the supply according to the required power. Two important voltage control techniques are commonly used for heating power control in ac power controller are Phase Control Switching (PCS) and Integral Cycle Control (ICC). In case that a PCS is used for the resistive load, it can produce higher order harmonics and heavy inrush current while switching on in a cold start. A feedback controlled digital circuit which provides for ICC of power in R-L loads is described. The significant feature of the circuit is that it rapidly and automatically adjusts the firing angle of the Power Semiconductor Device (PSD) to eliminate the undesirable dc component in the current of RL loads. Another notable feature of the circuit is that the initial conduction is started with firing angle = 90 which results in suppressed first peaks in the conduction bursts. Subsequently, the feedback takes over to make the firing angle at equal to the power factor angle, thereby triggering conduction at the current zero in each burst. This scheme of automatic dc offset elimination can be utilized to good advantage in the case of motor loads with rapidly changing power factors. The circuit is simple, inexpensive, and can be assembled easily using commercially available components. In the proposed method, a disadvantage of phase controlled is removed. In this paper authors have reported simulated results, design methodology and implementation of the ICC method for Welding application for R-L load.