Introduction Diodes in three-phase rectifier circuits of chp 7 are replacedby THYRISTORS Circuits in chp 8 are fully controllable average output voltage can be varied by controlling thetriggering input to the SCR gates in suitable manner. The three gate pulses are displayed by 120 relative to eachother, giving same delay angle to each SCR. Each SCR conducts for 120 after triggering and remain offfor 240. Full-Wave (Three-Pulse) Controlled Rectifiers With a Resistive Load Firing angle is measured from the intercestion of corresponding phase voltages and not the zero crossings of the voltage waves. When is varied, the segments of phase voltagethat fabricate the load voltage change, providinga control over the average value. Negative exursions of load voltage are possible,depending upon the nature of load. Firing angle = 0 Firing angle = 15 ( < 30) Firing angle 30