We have one Kinetsync regulator, Europe - Serbia, and recently had a lot of problem with starting our 2 MW synhronous motor .
Our amusing problem was DC voltage on rotor before start without input voltage on two impulse cards TRIG 3 .
we found that the voltage from the secondary transformers somehow over the thyristor and orthocopters is the cause of the problem with opening of the bridge and voltage before start that we temporarily solved by removing wires from cathode and gates at one thyristor .
we changed the thyristor but the failure or the malfunction was pointing to the other so our regulator is currently working with 5 thyristors in the bridge because the production was endangered.
Somewhere on the Internet we found the procedure for calibration and adjustment of 2 pulses cards . I suggest you do calibration because there may be a problem here somewhere. In addition, you are supposed to check the voltage on the secondary transformer and the fuse state .
Good luck