Hi Nigel,
You are right, my circuit has 3 zero cross detectors, 3 ramp generators, and three comparators between each of the ramps and one reference DC voltage, variable, following the algebraic sum of two sensing inputs.
Each time that the ramp crosses the reference, a driver is activated and feed an MOC random phase optocoupler .This happens following the phase sequence of the three phases.
Due to the presence of the 2 other phases it is not necessary to start firing from 0 degrees , in my first attempt I used 3 transformers connected in star to generate pulses lagging 30° the correspondent phase and I experiment the jump from 20-30 VDC to 150 and then continuolsy up to 300 . Then I modified the connection to delta to get control from 0 to 180 degrees, obtaining the same result.
Before to start a fully controlled version, doubling the number of 50A 800V SCRs and other less expensive components I am trying to get an expert answer to my fundamental doubt about the difference in the voltage output between a semi and a full controled rectifier with respect to the variation of the firing angle. And I am making reference to an ideal circuit, with a pure resistive load, a perfect sine wave, as that only viewed in the text books, and a perfect range of the firing angle.
Thank you so much for your support.