Hello
I am repairing an 30 years old machine, a Pfauter 320, where there was a DC servo drive without feedback (Heldt&Rossi), and the tachometer was used to setting the speed of other axises. Now, there is a Mentor 2 drive (from controltechnigues), which needs feedback. The problem is, that the old part uses the feedback unpolarised, meaning that there are 2 relays, so they always get 0-90V (the feedback is -90 to +90V). The problem is, that the Mentor 2 drive also connects one end of the tacho to 0V (ground), which is fine in one relay, but the other will try to swicth the signal - result both ends of the tacho is connetced to 0V, and we have a shortcurcuit (not to mention the problems it can cause). A retcifier is not a solution, as when the relays swicth in, it causes a change of 0,6volts. I have tought of that. Originally it was tought to get the feedback after the relays, as the Mentor 2 should be able to understand a non-polarised feedback, but now I now I know that it cannot.
The solution could be a DC/DC converter to isolete the 2 parts. Where can I get such a conveter, I need to transfer +/-92 volts to the same, but isolated. Do such things exists?
Main question: there are millions of things for automation, but this? A DC/DC isolated converter?
About Mentor 2 - if the tacho is swicthed, it goes MAD. So mad, that it cannot be stopped once gone wrong. Is there a way, to stop the drive in case of such fatal problems? I wonder why the drive does not react to that kind on problems. It is (was) possible due to the fact, that names and wirering and so forth is so much different 30 years later. I had to take a chance, then I found the drive going in sain, but when I took the "run" signals off it did not stop, I had to take the main power of (emergency stop also fails at this point by some reason, but that is probably another problem in the machine, unless the drive takes power from elsewhere causing other parts to fail)
WBR Sonnich Jensen