On Tuesday 08 May 2018 18:58:53 andy pugh wrote: > On 8 May 2018 at 14:27, John Kasunich <jmkasun...@fastmail.fm> wrote: > > Which cables have a braided shield? The ones taking DC power from > > the power supply to the drives? > > > > There's nothing magic about those cables - replace them with two > > suitably sized single-core wires. > > I know there is nothing magic, they are just some 3-core mains wire > that I had. (Multiflex SY). In fact I am pretty sure the braid is only > really meant for mechanical protection. > > > Is your drive DC supply floating (transformer) or rectified mains? > > Rectified mains. > > > If such a PE terminal exists, I would run the a PE lead from each > > motor frame tightly bundled or twisted with the motor power leads > > and back to the drive PE. (If the drive doesn't have a PE, I would > > make one using a pair of 0.1uF or so film caps with suitable voltage > > and safety ratings.) That provides a low inductance path for common > > mode current to return from motor frame to drive DC bus. The PE > > terminals of each drive could be connected to a common control > > chassis near the drives. The ferrite beads around the DC bus > > connections to the common power supply would encourage common mode > > currents to stay in each drive/motor loop instead of wandering off > > towards the supply and the other drives. > > There is no PE terminal on the STBL, so I have the STMBL on DIN rail, > and the motor earth cable (from the M23 connector) is connected to an > earthing block on that DIN rail. > Actually, at the moment, the earth wire isn't connected, I > disconnnected it to put the drive outside the machine as one of my > experiments. I intend to se if connecting makes things worse. > But I had a working machine and parts to be finished, so I stopped > experimenting and started machining. > > I will try what PCW suggests first (because it is easy) then if that > doesn't work I will look at this more scientific approach. > > > Are your motor leads shielded? That shield can DEFINITELY be > > counterproductive, since it acts as additional > > "motor-lead-to-ground" capacitance. > > No, the motor wires are not shielded. I thought that they were, but > inspection shows otherwise.
All my motor cables are twisted and shielded, usually quad core, with each motor pair being one wire and the one diametrically opposite, a variation use of the star-quad microphone cable. It totally rejects any noise source it may go by when actually used for a mic cable. But its just a hair light for motor cable, as it generates a just barely detectable heat rise. 24 to 26 gauge, so there is a bit of loss when the motor is amp'd up for strong performance, more than say 3.4 amps/coil. Not saying this is demanded, but its a data point that has worked fairly well here. -- 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) Genes Web page <http://geneslinuxbox.net:6309/gene> ------------------------------------------------------------------------------ Check out the vibrant tech community on one of the world's most engaging tech sites, Slashdot.org! http://sdm.link/slashdot _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
