Hi Brian:
Most hi-pot failures are clearances and sometimes creepage distances and seldom solid insulation. See Joe Randolph's paper at the May PSES Symposium on breakdown of ethernet connectors. All breakdowns are due to the peak voltage, whether ac or dc. The results are the same voltage (peak). If ac, then the tester must have sufficient current to drive the capacitance of the line filter. The minimum ac current is a multiple of the leakage current, either 1x or 2x the voltage ratio between the leakage current voltage and the hi-pot test voltage. (If the neutral was open during the leakage current test, then 1x; if the neutral was closed, then 2x.) If dc, then the rate of rise, dV/dt, must be adjusted to limit the line filter charging current to less than the hi-pot current rating. Failure is evidence of an arc, not necessarily a current trip of the hi-pot tester. An arc can occur, but not trip the hi-pot tester. Some hi-pot equipment includes an arc detect circuit as sometimes the arc is difficult to detect by a human. If there is a breakdown, repeat the test with a higher current to find the breakdown site. Sometimes, components must be removed one at a time repeating the hi-pot test to find the breakdown site. Rich - ---------------------------------------------------------------- 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.ieee-pses.org/emc-pstc.html Attachments are not permitted but the IEEE PSES Online Communities site at http://product-compliance.oc.ieee.org/ can be used for graphics (in well-used formats), large files, etc. Website: http://www.ieee-pses.org/ Instructions: http://www.ieee-pses.org/list.html (including how to unsubscribe) 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]>
