Any time you troubleshoot a large motor drive, you run the risk of both electric arc and electrical shock. Arc blasts are less frequent, but deadly. They’re most commonly caused by a dropped wrench or other tool that lands across high-energy bus bars in an open cabinet. This kind of short circuit is upstream of protective fuse links and lets loose thousands of amperes of fault current.
Electric arcs produce the highest temperatures on earth — up to 35,000 °F (19,426 °C) — causing all materials to vaporize and expand explosively. The blast pressure can throw a person across a room, and spray a person with shrapnel and molten metal droplets. Aside from the primary danger of being burned, intense pressure and sound can cause physical injury and deafness. The input power requirements for a large motor drive puts it in the high-risk category for arc flash.
Electrical shock is more commonplace. With a slip of the hand, you or your tool connects with a live component. It happens when you’re working too fast, just getting in there quickly to check one thing. Not as destructive as an arc blast, but still deadly.
Read the full article from Fluke’s Electrical News to learn how to guard against either of these dangers, especially when working on large motor drives.
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