> If possible, connect equal, very high value high-voltage > resistors > across the insulations so as to equalize the voltages. The > resistance > value clearly needs to be lower than the lower of the two > insulation > resistances, but with modern insulations, you may be able to > use 50 > Mohms or more.
At first glance, this seems to be a reasonable and effective solution. However, on further consideration, I believe the capacitance across the insulation is a more significant factor than the insulation resistance. If this is the case, then the resistance values must be much less than the capacitive reactance so that the resistance is the dominant current path and effectively divides the voltage across each insulation (which is the same principle as for insulation resistance mentioned above). The values of the resistor values are not critical if the insulation is subject to mains-frequency sinusoids. However, if the insulation is subject to impulses such as the 1.2x50 impulse, then to divide the impulse the time-constants of the two RCs must be equal. R1C1 equals R2C2. Best regards, 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]>
