Think 50/60Hz -> X = 2*pi*f*L and the other 'X' for the representative freq for that step response -> think about Q = X/R for principle freqs.
Think about capacitance between windings for a very hi-V step response. Think about what the L in ground may do to conducted emissions for the power supply. Think about the ground bond test in CSA 0.4, and performance requirements in NFPA 70. And if you are really really worried about the big surge, look at FAA 019E and NFPA 780. FWIW, recently did a 5000VA device with this construction - no problems, but the choke used 12ga wire and huge ground straps. Brian From: [email protected] [mailto:[email protected]]On Behalf Of Dean Gerard (Medical Physics) Sent: Thursday, October 15, 2009 3:53 AM To: [email protected] Subject: inductive filter in PEC I'd be grateful for people's views on the wisdom of including an inductive filter (for fast transient suppression) in the protective earth conductor of a device. Since safety in the event of a fault to earth relies. in most installations. upon automatic disconnection of supply, which in turn relies upon low-impedance earth-fault loop, does the inclusion of an inductance in this loop not then compromise this safety feature by potentially increasing disconnection time in the event of such a fault? (the shock hazard being a function of duration as well as magnitude) Furthermore, that part of earth-loop impedance attributable to the device, rather than the installation, is tested by DC earth bond resistance measurement. How valid a measure is this with an inductance present, since the earth-fault will not be DC but at mains frequency and typically generated as a transient step-type function when the fault occurs (to which the inductance will present a much higher impedance). Thanks Ged Dean - This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. To post a message to the list, send your e-mail to <[email protected]> All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc Graphics (in well-used formats), large files, etc. can be posted to that URL. Website: http://www.ieee-pses.org/ 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]>
