On 12/26/2015 07:36 PM, John Thornton wrote: > You misunderstand, all those components are internally grounded I did > not ground any of them. I just showed that the shell on each component > is bonded to the ground connection on each device.
Ok, now the real question is whether you can see the difference wrt. to my drawing. The trick is that there should never ever be two or more paths for the current to flow, even if it is just an earth connection (or GND for that matter). The isolation barrier I drew is the low-to-high-power separation. It should be kept physically separated everywhere until you join the power and earth connections at the power supply input. The real problem I see is the connection of the VFD controller to the computer's serial port. Apparently, the computer and the VFD controller both have the GND connected internally to earth. I am pretty sure that the computer's GND is connected to the earth (chassis) of the computer (most PCs have). The VFD controller probably has the same connection, where the modbus serial port's GND is connected to the VFD controller's earth (chassis). If so, then you need to break that loop by electrically isolating the serial port. -- Greetings Bertho (disclaimers are disclaimed) ------------------------------------------------------------------------------ _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
