I would expect a 50/60Hz transformer to be a very poor transformer at 150kHz. The leakage inductance alone would attenuate the signal substantially. The iron laminate material in the core would also be very lossy at that frequency.
Ralph McDiarmid, AScT Compliance Engineering Group Xantrex Technology Inc. www.xantrex.com From: Ken Javor [mailto:[email protected]] Sent: April 29, 2003 12:33 PM To: John Woodgate; [email protected] Subject: Re: FCC Limits At one time I needed to perform MIL-STD-462 power line audio frequency susceptibility test CS01, which places the secondary of a transformer in series with power to the test sample. The primary side is driven by an audio amplifier of low source impedance. In the US, the sole source of the mil-spec version of this transformer is Solar Electronics. Before I had one of theirs, I just went out and bought a 2:1 step down ratio transformer (like the Solar model) that was built just for 60 Hz, and it worked fine in my application. So that's why I think a 50/60 Hz transformer built for 230 Volts will attenuate input 150 kHz ripple by twice as much as a transformer built for 120 Vrms. > From: John Woodgate <[email protected]> > Reply-To: John Woodgate <[email protected]> > Date: Tue, 29 Apr 2003 19:21:57 +0100 > To: [email protected] > Subject: Re: FCC Limits > > > I read in !emc-pstc that Ken Javor <[email protected]> wrote > (in <bad41a21.1ef6%[email protected]>) about 'FCC Limits' on > Tue, 29 Apr 2003: >> I am interested in opinions on the matter of the FCC changing their >> CE limits to include frequencies down to 150 kHz. My concern is >> predicated on the following assumptions: >> >> a) CISPR 22 controls to 150 kHz because European radios broadcast >> down to that frequency. That is called the long wave band > >> . > Quite right. Well, almost, we are supposed to call it 'ow Frequency' > now. > >> In >> North America, AM broadcasts are confined to the medium wave band. >> The 450 kHz cut off includes the AM band IF. > > The preferred IF in Europe is 450 kHz, since that minimises problems > with image interference even for the French LF stations. >> >> b) (Most?) European single phase power is 220 Volts, 50 Hz. The >> transformers in radio power supplies have a different turns ratio >> than for American single phase power at 120 Volts. > > 230 V now. but with tolerances that admit 220 V. >> >> c) In my experience, a generic 50/60 Hz transformer works just as >> well at 150 kHz as it does at the power line frequency. > > That is astonishing. At 150 kHz, I would expect a power transformer to > look like a network of capacitors. >> >> In view of the above, it is not obvious to me why the FCC adopted >> CISPR 22 CE limits. Does anyone know if LW broadcasts are planned >> for North America? If that were to happen, the CISPR 22 limits at >> 150 kHz would need to be reduced roughly 6 dB, to account for the >> reduced turns ratio in power supplies built for North American >> power. European transformers would attenuate power line ripple >> more than American transformers would. > > I don't see why, since the capacitances are the dominant transfer > router. > -- > Regards, John Woodgate, OOO - Own Opinions Only. http://www.jmwa.demon.co.uk > Interested in professional sound reinforcement and distribution? Then go to > http://www.isce.org.uk > PLEASE do NOT copy news posts to me by E-MAIL! > > ------------------------------------------- > 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. 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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
