Hi David, A couple of possibilities:
- You have an increase in RF currents flowing from the power supply, through the electronic load, to it's power source (regardless whether the electronic load is grounded). Note: EN55022:1998, clause 9.2.e says that other power cords from the system (in this case, your electronic load) need to be connected to their own artificial mains network. - The volume of the electronic load is much bigger than the resistive load, and has more capacitance to the ground plane of the test setup. - Emissions testing is very sensitive to wire length and position. We normally do EMC testing with a resistive load, using wires as short as practical. A customer once reported a difference in readings when he tested our power supply with a resistive load. When I asked for a picture of the test setup, I saw his resistive load and hookup wire formed a loop about 2 feet in diameter. When I re-created his resistive load from the picture, I saw an increase in my own noise measurements of 10dB. Pat Lawler EMC Engineer Condor DC Power Supplies emc-p...@ieee.org wrote on 05/18/2006 08:08:46 AM: > We measured conducted emissions of a switched mode ac-dc power supply > and found that emissions are much higher when using an electronic load > compared to a resistive load. Can somebody explain why this is? > Thanks, > David. > > David Gelfand, P.E. > Product Integrity Engineer > Mitec Telecom Inc > 9000 Trans-Canada Highway > Montreal QC H9R 5Z8 > Canada > 514 694 9000 x2262 - ---------------------------------------------------------------- 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 emc-p...@ieee.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 emcp...@ptcnh.net Mike Cantwell mcantw...@ieee.org For policy questions, send mail to: Jim Bacher: j.bac...@ieee.org David Heald: emc-p...@daveheald.com All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
