This "S21 Regulator" sounds a lot like the "Induction Master" used on P&H Static Stepless Crane controls,
but I don't remember any phase shifting being involved.
It would be helpful to know what the PLC is controlling, reversing contactor or a ac/dc drive and if any work was done on these devices. Most PLC I/O cards have integral indicators showing the active output/inputs...is the "run command" active in the PLC? if not you have a hardware or field...
"Can you help me with the "A" side also?"
Here the project file..Its a bit larger and I am not sure if ther are file size limits on the uploads.
http://files.engineering.com/getfile.aspx?folder=c53bfe14-0454-4acd-897d-984d827582af&file=32635a.xps
I have been tasked with coverting a contactor style magnet control to a DC drive control. This application requires a short(100ms) counter-excitation at the end of a short dwell time at the end of a stacking operation. my max. current load is 42amps. using a 56amp regenerative dc drive. What...