Re: Site Correlation
I am quite familiar with 61000-4-6. But it is an immunity requirement and has nothing to do with the current thread, which is about controlling cm EMISSIONS on cables. I suppose one could use a CDN designed for injection as a measurement tool, but the absorbing clamp is so superior - it can be used on all types of cables, and it works up to 1 GHz, whereas CDNs are designed for no more than 230 MHz. The fact that the CDN works well below 30 MHz, all the way down to 150 kHz is immaterial - RE requirements start at 30 MHz, and in any case the absorbing clamp makes a superb current probe at 150 kHz - anyone wanting a transfer impedance for that device let me know. For those interested, my website includes a quite complete discussion on the pros and cons of using conducted techniques to simulate radiated immunity coupling, with a discussion of the corresponding emissions discussion in the introduction. Go to www.emccompliance.com, push the EMC INFO button, select the download page, and skip to the last selectable item, which is a paper I presented at the '97 IEEE EMC show in Austin, On Field-To-Wire Coupling Versus Conducted Injection Techniques. Ken Javor -- From: CE-test - Ing. Gert Gremmen - ce-marking and more... cet...@cetest.nl To: Ken Javor ken.ja...@emccompliance.com, Cortland Richmond 72146@compuserve.com, ieee pstc list emc-p...@ieee.org Subject: RE: Site Correlation Date: Sun, Jan 14, 2001, 1:10 PM Hi Ken, Again you should definitely study EN 61000-4-6. It assumes cable to have an impedance level (CM) of 150 Ohms, a good average for many situations. It uses a coupling/decoupling network matched to 150 ohms that feeds RF interference from or to the cable in common mode. Many CDN's exist therefore adapted to the cable type. The CDN approach makes high reproducibility possible, as it is not very difficult to maintain a stable 150 Ohm real impedance up till say 100 MHz. For complex cable types a current clamp is used in a special version. Using low generator voltages high level immunity test are allowed, due to the resistive coupling. The basic CDN consist of only 3 components 1 R, 1 C and 1 L. Due to the well defined CM impedances and because cables leaving the EUT are lead over a ground plane at 30 mm height, the wire part up till the CDN is not much losing it's power (characteristic impedance) over the 30 cm allowed to the CDN. Regards, Gert Gremmen, (Ing) ce-test, qualified testing === Web presence http://www.cetest.nl CE-shop http://www.cetest.nl/ce_shop.htm /-/ Compliance testing is our core business /-/ === -Original Message- From: owner-emc-p...@ieee.org [mailto:owner-emc-p...@ieee.org]On Behalf Of Ken Javor Sent: Sunday, January 14, 2001 12:45 AM To: Cortland Richmond; ieee pstc list Subject: Re: Site Correlation I think you misunderstood a couple of my arguments. A CE limit on cables would not pre-empt the RE test, it would simply remove the cables as radiation sources, thereby eliminating the need to arrange them for maximum radiation. A cable CE limit would be based on an ideal maximum radiation orientation, therefore in practice measured radiation from a CE compliant cable would always be below the RE limit. The size of the EUT would not play a role, since you would always perform the RE test. And finally, I specifically talked about the absorber clamp because it damps out standing waves - the only issue, as Ing. Gremmen pointed out earlier, is how close can you get the clamp to the EUT - it must be within a small fraction of a wavelength - say 0.1 lambda. Ken Javor -- From: Cortland Richmond 72146@compuserve.com To: Ken Javor ken.ja...@emccompliance.com, ieee pstc list emc-p...@ieee.org Subject: Re: Site Correlation Date: Sat, Jan 13, 2001, 5:34 PM Ken, When you ask how members feel, you open a Pandora's box! We must still meet some kind of installed bottom line; our equipment must not generate fields above some limit. (We can argue what that should be some other time.) However, when _designing_ an EMC solution, we can estimate field strength based on some arbitrary gain, current and impedance for cables. By assuming all common-mode currents flow in the worst possible directions -- here's our cable arrangement -- we come up with a conservative solution. But cables coming from a (say) two-meter square EUT cannot take all possible configurations. GR-1089 assumes a limited cable arrangement representative of a Central Office installation. And when an EUT gets large enough, it's no longer enough to know what current flows in the cables anyway, because the EUT may be a principal radiator by itself. So I'd not want all radiated tests replaced. We sill need a size limit to tell when we must use antennas, and when current probes. We also need a more flexible definition how and where cable
RE: Site Correlation
Hi Ken, Again you should definitely study EN 61000-4-6. It assumes cable to have an impedance level (CM) of 150 Ohms, a good average for many situations. It uses a coupling/decoupling network matched to 150 ohms that feeds RF interference from or to the cable in common mode. Many CDN's exist therefore adapted to the cable type. The CDN approach makes high reproducibility possible, as it is not very difficult to maintain a stable 150 Ohm real impedance up till say 100 MHz. For complex cable types a current clamp is used in a special version. Using low generator voltages high level immunity test are allowed, due to the resistive coupling. The basic CDN consist of only 3 components 1 R, 1 C and 1 L. Due to the well defined CM impedances and because cables leaving the EUT are lead over a ground plane at 30 mm height, the wire part up till the CDN is not much losing it's power (characteristic impedance) over the 30 cm allowed to the CDN. Regards, Gert Gremmen, (Ing) ce-test, qualified testing === Web presence http://www.cetest.nl CE-shop http://www.cetest.nl/ce_shop.htm /-/ Compliance testing is our core business /-/ === -Original Message- From: owner-emc-p...@ieee.org [mailto:owner-emc-p...@ieee.org]On Behalf Of Ken Javor Sent: Sunday, January 14, 2001 12:45 AM To: Cortland Richmond; ieee pstc list Subject: Re: Site Correlation I think you misunderstood a couple of my arguments. A CE limit on cables would not pre-empt the RE test, it would simply remove the cables as radiation sources, thereby eliminating the need to arrange them for maximum radiation. A cable CE limit would be based on an ideal maximum radiation orientation, therefore in practice measured radiation from a CE compliant cable would always be below the RE limit. The size of the EUT would not play a role, since you would always perform the RE test. And finally, I specifically talked about the absorber clamp because it damps out standing waves - the only issue, as Ing. Gremmen pointed out earlier, is how close can you get the clamp to the EUT - it must be within a small fraction of a wavelength - say 0.1 lambda. Ken Javor -- From: Cortland Richmond 72146@compuserve.com To: Ken Javor ken.ja...@emccompliance.com, ieee pstc list emc-p...@ieee.org Subject: Re: Site Correlation Date: Sat, Jan 13, 2001, 5:34 PM Ken, When you ask how members feel, you open a Pandora's box! We must still meet some kind of installed bottom line; our equipment must not generate fields above some limit. (We can argue what that should be some other time.) However, when _designing_ an EMC solution, we can estimate field strength based on some arbitrary gain, current and impedance for cables. By assuming all common-mode currents flow in the worst possible directions -- here's our cable arrangement -- we come up with a conservative solution. But cables coming from a (say) two-meter square EUT cannot take all possible configurations. GR-1089 assumes a limited cable arrangement representative of a Central Office installation. And when an EUT gets large enough, it's no longer enough to know what current flows in the cables anyway, because the EUT may be a principal radiator by itself. So I'd not want all radiated tests replaced. We sill need a size limit to tell when we must use antennas, and when current probes. We also need a more flexible definition how and where cable current is to be measured. Not al cables can be run along the floor on a reasonable test site. If we must reach a current maximum with a probe, we may have to get five meters from the EUT. That might require a ten meter diameter ground plane -- which brings to mind the saying: Be careful what you ask for; you might get it! Regards, Cortland (Whose posting here reflect none of his employer's opinions) == Original Message Follows Date: 13-Jan-01 00:50:16 MsgID: 1077-20414 ToID: 72146,373 From: Ken Javor INTERNET:ken.ja...@emccompliance.com Subj: Re: Site Correlation Chrg: $0.00 Imp: Norm Sens: StdReceipt: NoParts: 1 Date: Sat, 13 Jan 2001 02:43:51 -0600 Subject: Re: Site Correlation From: Ken Javor ken.ja...@emccompliance.com Reply-To: Ken Javor ken.ja...@emccompliance.com I must say that this thread has been a refreshing alternative to the EMC-law/regulations questions that typically occupy this service. Not complaining either, because If I suddenly found myself working commercial EMC issues I would likely be flooding this line with those self-same questions. Almost as an aside, Mr. Heald raises an issue of enduring interest to myself and others. Another important factor... is to manipulate the cables during testing (oh, how much easier our job would be without cables). The same issue was raised parenthetically in my answer to the question about GTEM
Re: Site Correlation
Actually since you mention it my application for cable cm CE control covered the spectrum from 150 kHz to 200 MHz! But the application was aerospace-related. I have to say, however that I think an I/O cable would be driven by PCB ground noise, which would be clock-speed related, not power supply switching-speed related. Ken Javor -- -- From: Ralph Cameron ral...@igs.net To: Ken Javor ken.ja...@emccompliance.com, David Heald dhe...@curtis-straus.com, Tudor, Allen allen_tu...@adc.com Cc: EMC-PCST \(E-mail\) emc-p...@majordomo.ieee.org Subject: Re: Site Correlation Date: Sun, Jan 14, 2001, 7:57 AM Ken: I like the idea of setting a limit to common mode currents on attaching cables but mI wonder why CISPR has chosen to start such measurements at 30Mhz when most of the common mode currents are the result of switching products and are generated harmonically from the fundamental and as such propagate from the low Khz range up through 30Mhz. is there no consideration for those who occupy the spectrum below 30Mhz? In my applications of common mode suppression, almost every case, the source generating the common mode currents , when suppressed with simple external common mode chokes, satisfactorily reduced all the localized radiation caused by such effects. Series common mode chokes not only suppress the outgoing but reduce the incoming common mode currents that have the same potential for casuing equipment malfunction. Ralph Cameron EMC Consulting and Suppression of Consumer Electronic Equipment (After Sale). - Original Message - From: Ken Javor ken.ja...@emccompliance.com To: David Heald dhe...@curtis-straus.com; Tudor, Allen allen_tu...@adc.com Cc: EMC-PCST (E-mail) emc-p...@majordomo.ieee.org Sent: Saturday, January 13, 2001 3:43 AM Subject: Re: Site Correlation I must say that this thread has been a refreshing alternative to the EMC-law/regulations questions that typically occupy this service. Not complaining either, because If I suddenly found myself working commercial EMC issues I would likely be flooding this line with those self-same questions. Almost as an aside, Mr. Heald raises an issue of enduring interest to myself and others. Another important factor... is to manipulate the cables during testing (oh, how much easier our job would be without cables). The same issue was raised parenthetically in my answer to the question about GTEM polarization. The issue is control of cable-sourced radiated emissions. I am now about to allegorically take a baseball bat to a hornets' nest... Bela Szentkuti pointed out almost twenty years ago that it would be much more efficient and accurate to analytically/experimentally determine the relationship between cable common mode currents and the resultant radiated field based on the maximum possible radiation efficiency of that cable, and use that relationship to derive a common mode current limit for cables from 30 MHz to 1 GHz, using the absorbing clamp as a measuring tool. This would speed up OATS or any other kind of RE testing by deleting the requirement to maximize cable radiation. So this question is a poll. How do the subscribers to this service feel about cable common mode current control in lieu of direct measurement of cable-sourced RE measurement? The idea being that first you would measure and bring cable cm CE into compliance with a cable-type limit and only then would you make the RE measurement. The cables would only be support equipment which did not contribute to the RE profile, hence any measured emissions at or near the limit would be guaranteed EUT enclosure-related. Polite responses only, please!!! Ken Javor -- From: David Heald dhe...@curtis-straus.com To: Tudor, Allen allen_tu...@adc.com Cc: EMC-PCST (E-mail) emc-p...@majordomo.ieee.org Subject: Re: Site Correlation Date: Fri, Jan 12, 2001, 9:36 AM Greetings again. I received some questions about this off list and there has been more discussion in this direction, so I thought I would throw my other two cents in. For small fully anechoic chambers with little room for antenna height adjustment, you should be able to have uncertainty of about 6dB or so (10dB is much safer realistically) when you apply correction factors for a 10m site. The reason for this is, as John Barnes pointed out, the absence of reflected waves being received in addition to the direct waves. The key importance to a fully lined chamber (including the floor) is that destructive waves are not present. With a reflective floor, destructive waves can lower your readings by more than 30dB. Add this to the 6 dB or so of uncertainty for additive waves and your total error could be enormous. With an absorber lined floor, the influence of the destructive waves is eliminated or reduced, so a correlation of 6dB (again 10dB is safer) should be achievable (this
Re: Site Correlation
Ken: I like the idea of setting a limit to common mode currents on attaching cables but mI wonder why CISPR has chosen to start such measurements at 30Mhz when most of the common mode currents are the result of switching products and are generated harmonically from the fundamental and as such propagate from the low Khz range up through 30Mhz. is there no consideration for those who occupy the spectrum below 30Mhz? In my applications of common mode suppression, almost every case, the source generating the common mode currents , when suppressed with simple external common mode chokes, satisfactorily reduced all the localized radiation caused by such effects. Series common mode chokes not only suppress the outgoing but reduce the incoming common mode currents that have the same potential for casuing equipment malfunction. Ralph Cameron EMC Consulting and Suppression of Consumer Electronic Equipment (After Sale). - Original Message - From: Ken Javor ken.ja...@emccompliance.com To: David Heald dhe...@curtis-straus.com; Tudor, Allen allen_tu...@adc.com Cc: EMC-PCST (E-mail) emc-p...@majordomo.ieee.org Sent: Saturday, January 13, 2001 3:43 AM Subject: Re: Site Correlation I must say that this thread has been a refreshing alternative to the EMC-law/regulations questions that typically occupy this service. Not complaining either, because If I suddenly found myself working commercial EMC issues I would likely be flooding this line with those self-same questions. Almost as an aside, Mr. Heald raises an issue of enduring interest to myself and others. Another important factor... is to manipulate the cables during testing (oh, how much easier our job would be without cables). The same issue was raised parenthetically in my answer to the question about GTEM polarization. The issue is control of cable-sourced radiated emissions. I am now about to allegorically take a baseball bat to a hornets' nest... Bela Szentkuti pointed out almost twenty years ago that it would be much more efficient and accurate to analytically/experimentally determine the relationship between cable common mode currents and the resultant radiated field based on the maximum possible radiation efficiency of that cable, and use that relationship to derive a common mode current limit for cables from 30 MHz to 1 GHz, using the absorbing clamp as a measuring tool. This would speed up OATS or any other kind of RE testing by deleting the requirement to maximize cable radiation. So this question is a poll. How do the subscribers to this service feel about cable common mode current control in lieu of direct measurement of cable-sourced RE measurement? The idea being that first you would measure and bring cable cm CE into compliance with a cable-type limit and only then would you make the RE measurement. The cables would only be support equipment which did not contribute to the RE profile, hence any measured emissions at or near the limit would be guaranteed EUT enclosure-related. Polite responses only, please!!! Ken Javor -- From: David Heald dhe...@curtis-straus.com To: Tudor, Allen allen_tu...@adc.com Cc: EMC-PCST (E-mail) emc-p...@majordomo.ieee.org Subject: Re: Site Correlation Date: Fri, Jan 12, 2001, 9:36 AM Greetings again. I received some questions about this off list and there has been more discussion in this direction, so I thought I would throw my other two cents in. For small fully anechoic chambers with little room for antenna height adjustment, you should be able to have uncertainty of about 6dB or so (10dB is much safer realistically) when you apply correction factors for a 10m site. The reason for this is, as John Barnes pointed out, the absence of reflected waves being received in addition to the direct waves. The key importance to a fully lined chamber (including the floor) is that destructive waves are not present. With a reflective floor, destructive waves can lower your readings by more than 30dB. Add this to the 6 dB or so of uncertainty for additive waves and your total error could be enormous. With an absorber lined floor, the influence of the destructive waves is eliminated or reduced, so a correlation of 6dB (again 10dB is safer) should be achievable (this simply accounts for the absence of constructive interference). Another important factor to ensure you don't have any surprises when moving from precompliance to a compliance run is to manipulate the cables during testing (oh, how much easier our job would be without cables). Large signal strength changes can be achieved just by moving cables a few inches. I also have to agree with Gert's and Ken's comments on far field measurements. I mentioned this in my original message, but didn't elaborate at all. These are very important considerations that can greatly affect any expected correlation to a 10m OATS. -- David Heald
Harmonics motor life - an abstract
PSNet, Here's a reference to an article that might be of interest... - - - - - IEEE Transactions on Dielectrics and Electrical Insulation Vol. 7 No. 6, December 2000 A Quantative Approach to Estimate the Life Expectancy of Motor Insulation Systems by Hashem Oraee Sharif University of Technology Iran ABSTRACT Electric motors represent the largest single load in most power systems. With continuing increase in nonlinear loads, the effects of harmonic contents of power systems on various components is becoming more important. This paper is concerned with the effect of power system harmonics and voltage unbalance on the useful life of electric motors. A simple equivalent circuit is used to calculate the additional heat losses caused by supply distortions. A lumped parameter thermal network is proposed to calculate the resulting heat distribution within the machine. An Arrhenius chart is then used to estimate motor insulation remaining life. The proposed approach is used to determine the effect of supply harmonics and voltage unbalance on the useful life of a three-phase induction motor and the results are verified experimentally. - - - - - As at other times, I am not a library nor can I provide copies. Get your copy from your local technical library. br, Pete Peter E Perkins, PE Principal Product Safety Consultant Tigard, ORe 97281-3427 503/452-1201 fone/fax p.perk...@ieee.org --- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Jim Bacher: jim_bac...@mail.monarch.com Michael Garretson:pstc_ad...@garretson.org For policy questions, send mail to: Richard Nute: ri...@ieee.org
