Circuit Operation

The operation of the circuit has been described in the earlier pages. One pair of SCRs conducts at a time, producing a bridge output voltage containing significant ripple content. Since the current through an inductor cannot change suddenly, the inductor in the dc link tries to maintain the current passing through it as a steady value, which in turn means that the ripple content of the current through it reduces. Nevertheless it does contain some ripple and this ripple in the inductor current causes some ripple in the capacitor voltage, whereas the current through the load can be more or less a steady value. The effectiveness of the filter circuit depends on the values of the inductor and the capacitor. The larger they are, the higher the reduction in the filter content is. Of particular interest is the comparison of the bridge output voltage and the capacitor voltage. The ripple in the capacitor voltage is almost out-of-phase with the ripple in the bridge output voltage. This aspect is important when the output voltage across the load resistor is to be controlled in closed loop.

 
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