I was working off IEC 1000-4-6 (1996), Figures 2 and 5b, which cover direct injection and show the EUT isolated above ground. Figure 6 shows clamp injection and EUT isolation above ground. What you are referencing is a special case in the annex when the cm 150 Ohm impedance cannot be met. The theory is, I believe, as I stated before. Incidentally clamp injection is fundamentally different than CDN injection. CDN injects line-to-ground, and clamp injects in series with the cable. The standard specifically says that when using a clamp installed between EUT and AE, the AE must be an equal or lower impedance than the EUT. This is opposite of what you want with a CDN. My paper covers that issue in detail. It appeared in the 1997 IEEE EMC Symposium record, page 479.
Ken Javor > From: "Dan Kinney (A)" <[email protected]> > Date: Fri, 14 Feb 2003 16:22:37 -0500 > To: "'Ken Javor'" <[email protected]>, Oliver Betz > <[email protected]>, [email protected] > Subject: RE: Grounding of EUT in EN61000-4-6 conducted immunity test > > I have a hard time following Mr. Javor's reasoning. The standard provides > the option to use current clamp injection. Paragraph 7.3 states "The AE and > EUT with clamp injection shall represent the functional installation > conditions as close as possible e.g. either the EUT shall be connected to > the ground reference plane or placed on an insulating support (see figures > A.6 and A.7)." Figures A.6 and A.7 both clearly indicate the EUT may be > connected to ground. And I would contend, must be connected to ground if > the EUTs normal installation is such that the conductive case is connected > to grounded metal structures. Furthermore, if shielded signal are used in > the system, the shields must be connected to ground if they are to serve > their intended function. Often, this is through the conductive case of the > EUT. I would be interested in reading the article Mr. Javor wrote on this > topic. If I misunderstand the standard, perhaps the article will show me > the errors in my reasoning. Is the article available sir? > Dan Kinney > Horner APG > > > >> -----Original Message----- >> From: Ken Javor [SMTP:[email protected]] >> Sent: Thursday, February 13, 2003 1:46 PM >> To: Oliver Betz; [email protected] >> Subject: Re: Grounding of EUT in EN61000-4-6 conducted immunity test >> >> >> 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 > 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
