On Sunday 29 December 2019 05:37:36 andrew beck wrote: > Hey everyone > > So just getting to the bottom of these emails and thanks so much for > all the replies. > > There is much food for thought. > > If you missed it up in the emails here is the current plan for wiring > the control panel. > > yuhai servo drive manual > <https://drive.google.com/file/d/17inZoRboGQP3lqn0KHd343NlmDQ1CxzS/vie >w?usp=sharing> Linuxcnc mill control panel drawing > <https://drive.google.com/file/d/1rJYzUGXLrSKuDARQ878wc5RlkjgPqSCr/vie >w?usp=sharing> > > All the three phase stuff is pretty standard I think. The main > problem I have is that I am not sure how the grounding should work. > Eg do I tie the 24 volt powersupplies to ground on the input or output > etc and any safety stuff I need to make sure I do.
inputs for the 24 volts should be from a 240 hot and neutral. output rails minus to the green stuff, by a separate wire for each. + to wherever you need it, like field power for the mesa 7i76D. The ground symbol terminal on the psu's should goto that common bolt, again by its own wire. > The only opti isolation I have is in the mesa 7i76 card. Do the motor drivers not have opto's? > > So any thoughts feel free to let me know. I am planning on powering > this up tomorrow. > > Regards > > Andrew > > On Fri, Dec 27, 2019 at 8:03 AM Chris Albertson > <albertson.ch...@gmail.com> > > wrote: > > A ground loop is then a single device is connected to ground more > > than once. A good example is a motor driver. It might in a > > "power" input called "+" and "-" with the minus side grounded to the > > AC mains ground or a chassis frame ground. The in addition > > there is a logic level control signal that is "signal" and "ground" > > wires. This is a classic gound loop. > > > > How to break it? Use optical isolation on the signal. This places > > an air-gap in the control signal. The one that counts is in the motor drivers, the + and - signals from the mesa card there are both isolated from ground inside the driver. You can verify that with a dvm using the ohms scale, it s/b an open circuit to anyplace else but its coresponding opposite polarity terminal. > > > > Most of the time the system is not so simple as the above but the > > concept is the same, multiple ground connections are not good. > > Why? Because in theory current can flow if you have a loop but can > > never flow if there is not a closed loop. Then Ohm's law applies -- > > if there is current flow there is voltage drop. If the voltage > > drops across a gound then you have tow "grounds" that are not the > > same voltage. This can be really serious if the motors are large. > > > > There are a number of conventions that work. but they all do the > > same thing, they reduce the number of ground connects to one per > > "part" of the system. > > > > All the rules try to do the same thing, connect nuetral to ground > > ONLY at the building service entrance, use opto's on all signal > > lines. It is all the same idea > > > > > > _______________________________________________ > > Emc-users mailing list > > Emc-users@lists.sourceforge.net > > https://lists.sourceforge.net/lists/listinfo/emc-users > > _______________________________________________ > Emc-users mailing list > Emc-users@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/emc-users Cheers, Gene Heskett -- "There are four boxes to be used in defense of liberty: soap, ballot, jury, and ammo. Please use in that order." -Ed Howdershelt (Author) If we desire respect for the law, we must first make the law respectable. - Louis D. Brandeis Genes Web page <http://geneslinuxbox.net:6309/gene> _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
