From: lfresea...@aol.com [mailto:lfresea...@aol.com] Sent: Thursday, November 27, 2003 6:55 PM To: emc-p...@ieee.org Subject: 400 Hz filter
Hi All, looking for a filter for a shield room. Needs to be 400 Hz capable, and good for 230 Vac if possible. Anything above 30 Amps would be good. Anyone have one lying about on the shelf? Thanks, Derek N. Walton Owner, L F Research EMI Design and Test Facility Poplar Grove, IL 61065 Derek: When you say "400 Hz capable", it sounds like you intend to use it with other power frequencies (DC, 50 Hz, 60 Hz) as well as 400 Hz. Remember that at 400 Hz, the capacitive line current may be very significant (>10 amps), and the usual remedy for this is a "power factor correction coil" for each filter line. (The inductive reactance is adjusted to match the capacitive reactance, creating a parallel resonant "tank" circuit. Line current will drop significantly.) If you use the filter just for 400 Hz, you can leave the PF coils permanently connected. OTOH, if you use it for 60 Hz (or lower), then you might want to make the coil "switchable", so you can disconnect it. Regards, Ed Ed Price ed.pr...@cubic.com 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
