UPS System Switch Burnt


Thread Starter



i have a GUTOR UPS including 2 inverters and one bypass for them. i replace a fuse that blown before which located before static switch of the inverter. after we re-operated that inverter by the recommendation steps, explosion was occurred and the snubber across inverter static switch was burnt. after that we made a continuity test on all equipments and no problems noticed.

can you give me an approaching solution about this problem?

thanks alot..
Could you provide a bit more information regarding your UPS (voltage, number of phases, model number, how old, what type of snubber, etc..). Fuses and electrical explosions do not just occur. It is difficult to troubleshoot problem long distance, but what follows are some questions that may help you to start thinking about the problem, which may open the door to finding the cause of the problem and a solution.

Did you troubleshoot why the fuse blew before replacing it and re-energizing the UPS (always a good idea)? What else did you do troubleshooting wise prior to re-energizing the circuit and then after the explosion that you have not already mentioned (simple continuity checks do not always provide adequate troubleshooting information)? Did you inspect the UPS circuit downstream of the fuse? Did the fuse blow the second time around when you had the explosion? Did you have any downstream operation of overcurrent protective devices during this event? If the fuse did not blow, and the snubber did, the snubber was the "weak" point in the circuit and may have been defective or it may have been weaken by repeated operation due to a "smaller" problem. Did the UPS have any error codes or historical record of the problem? Do you have any trend graphs of the output of the UPS (e.g. voltage & current)? Did you talk to the manufacturer about your problem. If you are still having the difficulty, calling out an expert is many times a good troubleshooting step, Does your company have such an expert? If so, call him. If not, calling out the manufacturer service engineer is sometimes an effective (though costly) means for solving a difficult problem. Make sure you get an "expert" and not just a run of the mill service technician, otherwise, you may just get into to a finger pointing situation.

If you don't find anything, a first step would to repair the UPS, disconnect the line side of the UPS, and gently re-energize the UPS and see what happens. This should divide your problem in half (called the "Divide & Conquer" troubleshooting method). If nothing happens, your problem should be down stream of the UPS and you have some more investigative work to do. If you have a fuse blow or a snubber, then you have a UPS problem.

If the problem was not a defective snubber or UPS, then it would seems likely that you have a line to ground or line to line fault. I would inspect your wiring and connected equipment for signs or evidence of a downstream fault (burn marks, carbon tracks, smell, burnt or melted wire, etc.). I would meg your branch circuits wires to your subpanels to insure that you do not have a ground fault. Also, verify that you do not have a line to line fault. The line that your burnt snubber is on is a likely candidate to start your investigation.

As always, safety first when working around electrical circuits and equipment and always be respectful of the electrical and physical power and energy available in electrical circuits because it is just waiting to catch the unwary or respectful.

William (Bill) L. Mostia, Jr. PE
ISA Fellow, SIS-TECH Fellow,
FS Eng. (TUV Rheinland)
SIS-TECH Solutions, LP

"No trees were killed to send this message, but a large number of electrons were terribly inconvenienced." Neil deGrasse Tyson

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