On Saturday 02 January 2016 07:26:08 John Thornton wrote: > I do have a "control transformer" which can be identified by the three > fuses on top. One for X1 (secondary) and one each for L1 and L2. I > went back and found out which was X1 and X2 and will correct my wiring > today. My question is I have a filter on X1 and X2 should I ground > before or after the filter? > > JT > Thats a hard call John. I think I'd get out the scope & see which gave you the best noise rejection. To get rid of ground loops because the scope has a 3rd pin power plug, I'd power it from the transformer. But that would also make the ground after the obvious choice. YMMV of course.
> On 1/1/2016 6:41 PM, John Kasunich wrote: > > 120V transformer secondaries (in the USA) need to be grounded on > > one side, even if they are part of a machine control panel. > > > > Such transformers are referred to as "control power transformers" > > and traditionally powered electro-mechanical control devices such > > as relays and contactors. Today they still power those things, and > > they also power AC-to-DC supplies that run the electronic parts of > > the control. The low voltage DC power distribution (typically > > 24V) is sometimes un-grounded, sometimes single-point grounded, for > > exactly the noise reasons Berthos mentions. But the 120V "control > > power" isn't used a the "reference" for anything - it is still > > "dirty" power, although not as dirty as the main power that might be > > going to a VFD or whatever. 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> ------------------------------------------------------------------------------ _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
