Quote:
Originally Posted by Piotrsko
Your fuse is 2700 amps way too big. Max maybe 400 amps or what typical current your cables and control silicon are rated for. Im running 1000 amps for 10 secs and 250 continuous on a 300 amp fuse for 3 years now.
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The fuse I used is rated for protecting electronics (it was old stock from building 600VAC VFDs) and essentially protects against short circuit. The electronics do a good job of detecting overtemperature and overload conditions (they are rated as the overload device), so I don't really need (or don't THINK that I need, anyway) the fuse to do that for me.
I'll get a picture of the fuse and post it. I had never looked up the fuse curve (I think it is labeled 350A or something like that) until it blew and was quite surprised at how much current it took to blow. I'll post the fuse curve as well. I agree that it is too large - and that it OBVIOUSLY did not do it's job of protecting my electronics!
A 300A rated slow-blow fuse, if that's what you are using, will let through a lot of energy before the element melts. All of the industrial VFDs that I have taken apart use a fast-acting DC fuse on the DC bus. Siemens appears to use 2 fuses in most of their VFDs, one for the + buss and one for the - buss.