Massimo, Just to underscore what others have stated, long ago in one of the resistor mfr's catalogues, there was a discussion of this topic. Essentially, do not violate the DC wattage rating of the resistor based on a 1 second time period.
As an example, a 1W, 1 Ohm, carbon composition resistor should be able to handle a. 1A (or 1V potential) continuously, b. 2A (or 2V potential) at 50% duty cycle, i.e. 1/2 second duration, c. 4A at 25% duty cycle, i.e. 1/4 second duration, etc ... all the way up to the maximum voltage rating of the resistor. For a 600V rated resistor, this would mean the maximum pulse allowed would be 600V peak for less than or equal to 1/600th second or 1.6 milliseconds. This particular conclusion I have doubts about. I explain below. Fusing characteristics of wires is non-linear and therefore for large currents through a resistor (I don't know what that might be), I doubt the above. But for low currents, let's say less than 10 times the current rating of the resistor for the sake of argument (in the case above, that would mean anything less than 10 amps), I think that's acceptable. This is all spectulation and I am by no means an expert. But, if there is any question, please consult the mfr. - Doug McKean ------------------------------------------- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: emc-p...@hypercom.com Dave Heald: davehe...@mediaone.net For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org All emc-pstc postings are archived and searchable on the web at: http://ieeepstc.mindcruiser.com/ Click on "browse" and then "emc-pstc mailing list"
