Hi all, I have a system with all signals fully floating from electrical ground and chassis ground. Also the electrical grounds at the primary side 28Vlow (GNDA) and the secondary side GNDB are floating from the chassis ground (GNDM, case). The electronics inside are seen as non critical and can fail during a lightning test. So they are of no interest.
However 20 signals are very critical. These are 10 pairs going to 10 buttons on the keyboard. They are completely seperated from the rest of the electronics. Their state can be "Open / Close". To reduce the emissions on the lines, they are filtered with 10nF to the chassis ground. On this system we need to perform a ground injection according to the DO-160D, section 22, lightning induced transient susceptibility. We have to inject a voltage waveform 5A (750Vpeak, 40us /120 us) between the ground plane and the chassis of the isolated EUT. I guess that by doing this you would charge up the 10 nF filtering caps to 750V. However, since the signals are floating, the only way the capacitor can discharge is very slowly via their leakage current. This would give a waveform a lot longer than the 5A. Unfortunately I do not know the working of the test generators. Is the assumption correct that you will get a longer waveform or does the test generator take care of the return path to impose the timing of the waveform? As a result, the derating of my caps can be quite different. Any ideas are welcome, kind regards, Peter --------------------------------------- Peter Vuylsteke BarcoView Hardware Development Engineer Barco mailto:[email protected] tel: +32 (0)56 23 30 84 fax: +32 (0)56 23 35 88 Visit our site: http://www.barcoview.com BarcoView Theodoor Sevenslaan 106 B- 8500 Kortrijk Belgium - - - - - - - - DISCLAIMER - - - - - - - - Unless indicated otherwise, the information contained in this message is privileged and confidential, and is intended only for the use of the addressee(s) named above and others who have been specifically authorized to receive it. If you are not the intended recipient, you are hereby notified that any dissemination, distribution or copying of this message and/or attachments is strictly prohibited. The company accepts no liability for any damage caused by any virus transmitted by this email. Furthermore, the company does not warrant a proper and complete transmission of this information, nor does it accept liability for any delays. If you have received this message in error, please contact the sender and delete the message. Thank you.
