Doug when I ran my own section of a factory I forbad my testers from using the term "bad" or its military equivalent "NFG" on their failure tags although we saw the term many times on field returns. Bad isn't descriptive. Instead they were instructed to simply describe why they thought the unit was defective. This sounds complicated at first, but we quickly worked out some simple codes. i.e. ma=0 meant the unit didn't draw any current. If ma=0 then it was quite possible the fuse was open but the fuse was not the defect, rather a pointer to a latent defect.
On the other side fuses and fuse holders were probably the least reliable components we had with defect rates of 4 to 80%. Sometimes it was very confusing. A fuse that had opened because the current exceeded rating was not defective but merely a formally functional open fuse. Then again a fuse that was open before any current was passed was definitely a defective fuse. 125 or 180 ma fuses could be made defective merely by dropping them. We had some signaling fuses that would blow on over current but fail to signal. These were defective blown fuses. I fear I may have added to the "fog" but at least I never used the term "bad". Fred Townsend "POWELL, DOUG" wrote: Hello all,Recently, in my company, we've been discussing what exactly constitutes a good or bad fuse. In this industry we often hear that the trouble with a defective product was, "the fuse was bad." I occurred to me that the fuse is not bad, it performed exactly intended. In fact if the problem that caused the fuse to "operate" is still present, then the fuse is still good even though it is now an open circuit. The only time it can be a bad fuse is if it did not operate, resulting in shock or a fire.I have now have my ears tuned-in to this concept of a "bad fuse" and find it is commonly used all over the industry. In fact you can go to any number of websites that provide trouble shooting notes, and find instructions on how you can measure a bad fuse from a good fuse using an Ohm meter, photos included. And some of these instructions are from reputable manufacturers. Another term often used is "defective fuse", which in some way sounds more scientific, but is still fundamentally wrong.I recently saw a newspaper article that gave the explaination why electrical service was lost for over 100,000 people as a bad fuse. An investigation was under way to determine why the fuse went bad. This is a little like hearing the technologically uninitiated say "it must be a short somewhere", when the television set stops working.Maybe I am finicky, but this affects how companies view real product defects. When the "defect" is the bad fuse, then the real problem may be covered up. Often the answer is, increase the fuse size to prevent nuisance trips. The risk, of course, is that for every incremental increase in fuse value, you increase the risk of fire proportionally.Any thoughts or experiences?BTW - To all US citizens in the group, have a relaxing Memorial Day weekend.-doug Douglas E. Powell Regulatory Compliance Engineer Advanced Energy Industries, Inc. Fort Collins, CO 80535 USA _______________________________________________________________ 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.
