You can test the saturation point for yourself by simply passing a controlled DC current the core and coupling an impedance bridge to the inductor with a large value blocking cap in series with the meter. You can even use an electrolytic cap. Increase the current and watch the inductance change.
If possible, use an LCR bridge with something higher than a 1000 Hz test. -doug From: [email protected] [mailto:[email protected]] On Behalf Of David Cuthbert Sent: Friday, October 06, 2006 8:59 AM To: [email protected]; [email protected]; [email protected] Subject: RE: Inductor mystery Chris' comment on core saturation might be it. However, if your inductor is operating as a common-mode inductor, and has no DC flux, then core saturation will not be an issue. I did encounter a situation in which two solenoid inductors were placed quite close together and there was a substantial change if the magnetic fields were opposing of aiding - the direction they were inserted into the PCB mattered. Enough of anecdotal stories and on to the specific component. Let's examine the Coilcraft 1812CS-102XJLC inductor that you are using. The SRF is 310 MHz and the DC current rating is 480 mA. Coilcraft supplies S-parameters and a SPICE model for this part. This part looks very well behaved at 13.56 MHz. No parameters are changing much. I wonder if your EMI filter is tuned to resonance near 13.56 MHz? This would make the circuit more sensitive to variations in the inductor parameters. How much is the variation in conducted EM energy between a good and a bad inductor? Dave Cuthbert Linear Technology From: [email protected] [mailto:[email protected]] On Behalf Of [email protected] Sent: Friday, October 06, 2006 6:02 AM To: [email protected]; [email protected] Subject: Inductor mystery Dear Experts, We use the inductor part "1812CS-102XJLC" of Coilcraft in our RFID product as EMI filter. Continuously we face one issue, about 20 to 30 % products are functionally failing due to this inductor. While we change the inductor alone the product passes the functional tests. Hence we studied the characteristics of the inductor. Measurements carried out using the Agilent Impedance analyser 4294A shows the failing inductors and passing inductors are identical with respect to the below listed parameters for the entire measuring range of 40 Hz to 110 MHz. Our frequency of operation is 13.56 MHz and both the failing inductors and passing inductors are identical in this particular frequency also with respect to the below parameters. Is there anything else than the below listed parameters critical for an inductor? Has any one of you come across such an issue in your devices? I request your help. a. Ra.c b. Conductance - 'G' c. Reactance - 'X' d. Susceptance - 'B' e. Impedance - 'Z' f. Phase angle of the impedance g. Value of R, L & C measured using the equivalent circuit method of measurement. Sincerely K.Balasubramanian Project Leader - Hardware. - 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 [email protected] 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] All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc - 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 [email protected] 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] All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc This message, including any attachments, may contain information that is confidential and proprietary information of Advanced Energy Industries, Inc. The dissemination, distribution, use or copying of this message or any of its attachments is strictly prohibited without the express written consent of Advanced Energy Industries, Inc. - This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. 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