I agree with your additons and remarks. Regards,
Gert Gremmen -----Oorspronkelijk bericht----- Van: Robert F. Martin ITS/QS-Box <[email protected]> Aan: Ing. Gert Gremmen <[email protected]>; [email protected] <[email protected]>; Francis L. Fiedler <[email protected]> Datum: vrijdag 17 april 1998 14:39 Onderwerp: Re: Cable lengths needed >Gert; > >Certainly the coupling to a cable is dependent upon the frequency of the >signal and the cable's length. In the case of a product whose cables may >be 30-40 meters long, coupling may theoretically exist at frequencies >down to ~2.5MHz. There are a few considerations: > >1) the current radiated immunity standard (IEC 801-3:1984) tests down to >27MHz (quarter wavelength = ~2.8m) >2) the actual cable in Mr. Fielder's situation may be a quarter >wavelength at ~2.5MHz >3) EN61000-4-3 tests radiated down to 80MHz (quarter wave= ~1m), with >lower frequencies, as you mentioned, being tested using direct coupling >(EN61000-4-6) >4) IMO, cables should be exposed to the uniform field area (1.5m) and >then sufficient to exit the room >5) IEC 801-4/EN61000-4-4 require testing of cables that may exceed 3m in >length (although this length during test is not specified) >6) as you say, the cable LENGTH is rarely varied (per 55022) to maximize >emissions; 2.5 m is the practical limit on emission from a cable at >30MHz, with the real field variation coming from cable >orientation/coupling >7) the reality of testing!!- while it may not make engineering sense to >do emission testing with a cable longer than 2.5 meters, IMHO it doesn't >make sense to have a separate cable made for each different test (801-3, >1000-4-3, 1000-4-4, 55022/11) > >It is in consideration of all of the above that I recommend a minimum 3m >length for cables which may be significantly longer in production. > >As for the cable clamp in EFT, in a situation where a system includes 2 >'black-boxes' connected by a cable >3m, the clamp has to be placed first >at one end, and then at the other, which is why I generalized my >statement earlier. > >Regards; > >Bob Martin >Sr. Technical Manager >ITS - Northeast >(978)263-2662 >[email protected] > >The opinions expressed are my own and not necessarily those of my >employer. > > > ---------- >From: Ing. Gert Gremmen >To: Robert F. Martin ITS/QS-Box; [email protected]; Francis L. >Fiedler >Subject: Re: Cable lengths needed >Date: Thursday, April 16, 1998 3:58PM > >Hello Robert, Martin, > >As during emission testing and immunity testing cables act like >antennas, >we should treat them like antennas. The efficiency of a wire antenna is >a >sine function of its frequency and length. Therefore at a quarter >wavelength >optimum emission/receiption takes place. > >For emission testing cables longer then 2m50 meters (lowest F= 30 Mhz :: >10 >meters wavelength) don't make sense. In immunity testing the same >reasoning >is valid, but due to the limited uniform field area size only one meter >or >less of it is effectively participating in picking up signal. In TEM and >GTEM cells this length is even shorter. > >EN 55022 requires you to vary the length of the cables to maximise >emissions. This is most often >not practically realised. Instead max length cables (3 meters ore >more) >are used. > > >For this reason the IEC decided in their new standard (IEC 1000-4-3) to >start immunity testing at 80 Mhz instead of 30. The frequency below 80 >Mhz. >is extended to 150 Khz and is current injected into the cables using >coupling/decoupling devices. The philosophy is that at these lower >frequencies the contribution of cables is much higher as the enclosure >energy pickup.(IEC 1000-4-6) > >For EFT and the clamp, the end of the cable should be the end near the >apparatus under test. >I believe that is what you meant to write. For mains voltage the EFT >pulses >are galvanically coupled into the phase wires. > >Regards, > >Gert Gremmen Ing. > > >BTW is it standard or norm ; standardization or standardisation or >normalizing > I am not nativety speaking/writing this language (as you may >have >remarked) so please > group, can someone shine some light on these linguistical >topics. ? > > > >== Ce-test, Qualified testing == >Consultants in EMC, Electrical safety and Telecommunication >Compliance tests for European standards and ce-marking >Member of NEC/IEC voting committee for EMC. >Our Web presence: http://www.cetest.nl >List of current harmonized standards http://www.cetest.nl/emc-harm.htm >15 great tips for the EMC-designer http://www.cetest.nl/features01.htm > > > > > -----Oorspronkelijk bericht----- >Van: Robert F. Martin ITS/QS-Box <[email protected]> >Aan: [email protected] <[email protected]>; Francis >L. >Fiedler <[email protected]> >Datum: donderdag 16 april 1998 18:21 >Onderwerp: RE: Cable lengths needed > > >>It has been my philosophy is such cases, that a 3 meter length should be >>provided. >> >>During radiated emissions and immunity tests, a minimum of 1 meter >>should be exposed. In the case of immunity, the 1 meter should be in the >>'uniform' field area (even if you are not requiring the field uniformity >>test). The 3 meters then allows the cable to exit the enclosure. >> >>In the case of EFT, the standard specifies tests of cables >3 meters, >>and requires that the 1 meter coupling clamp be placed near the end of >>the cable. Using a 1 meter cable would be difficult because of the size >>of the clamp, and may also affect the results because of the potential >>for improved 'suppression' of the coupled transient via the support >>equipment. >> >>Bob Martin >>Sr. Technical Manager >>ITS - Northeast >>(978)263-2662 >>[email protected] >> >>The opinions expressed are my own and not necessarily those of my >>employer. >> ---------- >>From: Francis L. Fiedler >>To: [email protected] >>Subject: Cable lengths needed >>Date: Wednesday, April 15, 1998 6:24PM >> >>Greetings, >> >>Our equipment operates with cables that vary from two feet to two >>hundred feet in length. The length is dependent upon the customer's >>needs. Some cables are provided by the customer for their applications. >>We test our equipment to industrial environment using EN50081 and 50082. >> >> >>What length of cable do you think should be used for test purposes? The >>length of wire subjected to the test signal is usually one meter with >>additional 0.3 meters for positioning or decoupling purposes. Long >>length of wires can result in use of large areas and or bundling. Many >>test instructions specify not to bundle. >> >> >>All of your comments will be greatly appreciated. If you prefer to >>answer directly to me, your comments will be welcomed. >> >> >>Respectfully, >> >> >>Francis Fiedler >> > >
