>-----Original Message----- >From: John Woodgate [ mailto:[email protected]] >Sent: Saturday, December 06, 2003 8:05 AM >To: [email protected] >Subject: Re: Quandary > > > >I read in !emc-pstc that Ken Javor <[email protected]> wrote >(in <bbf5e462.7e99%[email protected]>) about >'Quandary' on Fri, >5 Dec 2003: >> I would say that the L and C elements of the filters are >tanking in >> such a way as to provide a little voltage amplification. >Although >> a 200 Watt load does not appreciably load the effect, I >expect that >> higher wattage loads would reduce the quality factor and it would >> go away. In the meantime you have to adjust the >generator setting >> for the desired potential inside the room. >> >I agree; there is no need to invoke non-linearity etc. to explain this. >If you tested the filter with a variable-frequency source and an audio >amplifier to give it a few volts to play with, you would probably find >that at around 500 Hz you get 1 kV inside the room! >-- >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!
Pretty good estimate, John! I did a quick circuit evaluation, using a double pi-section filter (three 10 uF capacitors & two 1 mH inductors), with a 1 ohm source impedance. Input was 120 Vrms, swept from 10 Hz to 10 kHz. If the load is open-circuited (actually, 100 k ohms), the filter output voltage will peak at 980 Hz & 2600 Hz, to about 2400 volts. If the load is 100 ohms, the filter output voltage will peak to about 1700 volts. If the load is 50 ohms, the filter output voltage will peak to about 1200 volts. Just for fun, why not model the exact inductance and capacitance of your filter to see what you get. Regards, Ed Ed Price [email protected] WB6WSN NARTE Certified EMC Engineer & Technician Electromagnetic Compatibility Lab Cubic Defense Applications San Diego, CA USA 858-505-2780 (Voice) 858-505-1583 (Fax) Military & Avionics EMC Is Our Specialty
