I haven't seen a response to this yet, so I will take a stab at it. Full disclosure: Except for the following paragraph, I am basically passing along what I learned from others on this excellent forum not all that long ago.
First off, my own comment. My expert :-) opinion is that EN61000-4-6 is really meant for equipment that was NOT designed to be electrically bonded to a metallic ground plane. I wrote and presented an article in part on that very subject several years ago. That said, here is what I learned on this forum. The test set-up is very clear that the EUT case and indeed its safety ground are NOT grounded, at least at the frequencies associated with the test. The power cord including safety ground go through a CDN which presents a 150 Ohm common mode impedance in series with the power cord. Any other EUT-connected cables get the same treatment. The EUT chassis and connected cables are supported above the ground plane at a height that is supposed to provide a 150 Ohm characteristic impedance. The purpose of all of this is to have a controlled impedance test set-up so that reflections are minimized. So the answer relative to the standard is that the EUT chassis should float and attached cables should be common mode ungrounded. Any grounds in these cables will see an rf impedance of 150 Ohms to ground from 150 kHz to 80 MHz. My own opinion again: From a technical point-of-view, if the equipment in service will be bonded to a ground plane and the attached cables will be be held in close proximity to a ground plane then the levels injected by EN61000-4-6 are higher relative to the assumed incident fields than they would be in situ. Equipment and cables installed close to and referenced to a ground plane have a lower antenna effective height than equipment installed far from and not referenced to a ground plane. Hope this helps. Ken Javor > From: "Oliver Betz" <[email protected]> > Reply-To: "Oliver Betz" <[email protected]> > Date: Wed, 12 Feb 2003 08:59:22 +0100 > To: [email protected] > Subject: Grounding of EUT in EN61000-4-6 conducted immunity test > > > Hello All, > > how shall conductive cases of a EUT (intended to be mounted to a > grounded metal construction in real life) be connected to the > reference plane during a EN61000-4-6 test: directly, via a resistor > or not at all? > > I remember only that (auxiliary?) earth connectors have to be > connected to ground via 150 Ohms, but I don't remember any word about > the case of the EUT. > > Thanks in advance, > > Oliver > > ------------------------------------------- > This message is from the IEEE EMC Society Product Safety > Technical Committee emc-pstc discussion list. > > Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ > > To cancel your subscription, send mail to: > [email protected] > with the single line: > unsubscribe emc-pstc > > For help, send mail to the list administrators: > Ron Pickard: [email protected] > Dave Heald: [email protected] > > For policy questions, send mail to: > Richard Nute: [email protected] > Jim Bacher: [email protected] > > Archive is being moved, we will announce when it is back on-line. > All emc-pstc postings are archived and searchable on the web at: > http://www.ieeecommunities.org/emc-pstc > This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: [email protected] with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: [email protected] Dave Heald: [email protected] For policy questions, send mail to: Richard Nute: [email protected] Jim Bacher: [email protected] Archive is being moved, we will announce when it is back on-line. All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
