I am not familiar with CISPR 15/EN50015, but other CISPR emission controls have a 30 MHz breakpoint between control of conducted emissions below that frequency, and control of electric field radiated emissions above it. Further, in my experience, if commercial standards other than aerospace or automotive do control radiated emissions below 30 MHz, they tend to use a 60 cm diameter electrostatically shielded loop, which of course controls magnetic emissions, not electric field. I would expect a lot of the low frequency (< 30 MHz) emissions from fluorescents to be electric field, based on the circuit impedance relative to 377 Ohms. For instance, a typical traditional (not compact) tubular fluorescent is rated at 40 Watts, which operating from a 120 Vac power source, is about 380 Ohms. Compact fluorescents (CFL) will be even more electric field predominant, since their power ratings are typically lower than 40 Watts. CFL electronic power supplies generate a rich spectrum of harmonics well below 30 MHz, which are more effectively controlled via conducted emission (CE) limits. CE control works better because the radiated emissions at these frequencies emanate more efficiently from the power wiring than from the bulb itself, and the wiring runs all over the home or office. This kind of radiated effect is more easily mathematically modeled than simulated with a typical test set-up, and therefore a conducted emission limit based on the model works better than a strictly radiated emission limit. As I have noted in this forum awhile back, the CE limit imposed on a single CFL is much relaxed from the CE limits imposed by CISPR 22 on ITE. Further, if a home is outfitted with CFL luminairies, there will be many of these bulbs, so that the net effect is that the lighting generates much more noise than even several desktop PCs. Mr. Woodgate is indeed correct that energy efficiency concerns are trumping EMI concerns; some countries are mulling bans on the sale of incandescent bulbs in order to decrease energy usage. If such bans become commonplace, or certainly in the class A world where fluorescent lighting predominates over incandescent, the control of PC and other ITE conducted emissions to levels orders of magnitude below those of much lower power luminaires might need to be reviewed.
Ken Javor Phone: (256) 650-5261 > From: John Woodgate <[email protected]> > Date: Thu, 13 Sep 2007 07:44:09 +0100 > To: [email protected] > Subject: Re: Fluorescent light noise > > In message > <off6f53536.11e4ba0e-on88257354.005174a1-88257354.0051c...@selinc.com>, > dated Wed, 12 Sep 2007, [email protected] writes: > >> However, the problem is that the lamps are used at distances much >> closer than the standard measurement distance. > > I'm not sure that 'however' is an appropriate response to my message; I > called attention to the importance of measurement distance. > > It may be that the common use at smaller distances was taken into > account in setting the emission limits in CISPR 15/EN 55015. > >> Certainly they are a problem in the design lab when trying to make >> sensitive measurements, > > That's a specialized application, and ipso facto, the people involved > know about the problem and how to fix it. > >> and also a problem in the home where a radio and fluorescent light may >> often be found close to each other. > > The same problem occurs with switch-mode power supplies, whether > powering the radio or something else. Energy efficiency regulations are > tipping the balance in favour of SMPS, ignoring this problem. The better > solution is to use a non-switching supply with a larger than > currently-used mains transformer, so that it has low no-load input > current, but these make the power supply larger, heavier and more > costly. > -- > OOO - Own Opinions Only. Try www.jmwa.demon.co.uk and www.isce.org.uk > There are benefits from being irrational - just ask the square root of 2. > John Woodgate, J M Woodgate and Associates, Rayleigh, Essex UK > > - > ---------------------------------------------------------------- > This message is from the IEEE Product Safety Engineering Society > emc-pstc discussion list. Website: http://www.ieee-pses.org/ > > To post a message to the list, send your e-mail to [email protected] > > Instructions: http://listserv.ieee.org/request/user-guide.html > > List rules: http://www.ieee-pses.org/listrules.html > > For help, send mail to the list administrators: > > Scott Douglas [email protected] > Mike Cantwell [email protected] > > For policy questions, send mail to: > > Jim Bacher: [email protected] > David Heald: [email protected] > > All emc-pstc postings are archived and searchable on the web at: > > http://www.ieeecommunities.org/emc-pstc - This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. Website: http://www.ieee-pses.org/ To post a message to the list, send your e-mail to [email protected] Instructions: http://listserv.ieee.org/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas [email protected] Mike Cantwell [email protected] For policy questions, send mail to: Jim Bacher: [email protected] David Heald: [email protected] All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc ______________________________________________________________________ This email has been scanned by the MessageLabs Email Security System. For more information please visit http://www.messagelabs.com/email ______________________________________________________________________
