Can I parallel multiple resettable fuses to achieve a higher current rating?
I assume you're talking about paralleling polyfuses- this is likely not a viable idea since the breaking capacity will be insufficient to interrupt any reasonable fault current, even if the current were to share nicely. When the last one in parallel opens it has to interrupt the entire fault current. I can almost smell the arcing..
You could consider a remotely resettable 500A DC circuit breaker, but I suspect once you get a price quote the customer will promptly reconsider how difficult it is to access a fuse that shouldn't be blowing very often anyway.
Those are rather decent fuses- low voltage drop, good interrupting capacity (3000A) and fairly widely available.
Paralleling fuses is technically possible, but is generally considered an extremely bad idea. Fuses, even those of the same rating, are just not identical. Nor are the fuse-holders they might be mounted in, or the lug screwed to them. All of that will affect the current sharing of an array of paralleled fuses. Even different temperatures can cause different fuses to carry different loads.
Generally, what happens with paralleled fuses, is that during one power cycle, inrush current will blow one, leaving the rest. Later on, another will blow, still leaving some. Eventually all will open.
Why not just move your specified fuse somewhere more accessible?
The existing answers may be misleading; it is acceptable to use multiple PTC fuses in parallel, as long as the following considerations are made:
- Each PTC fuse individually has an acceptable maximum current rating.
- The parallel tripped resistance of all the parallel PTC fuses is high enough.
- The conductors for any single fuse can handle the full load during the tripping period.
- The PTC fuses are placed far enough from each other that they don't co-heat.
There is some variability in the PTC fuses' internal resistance, but as the array of parallel PTC fuses self-heats, their resistances will match.
When current exceeds the trip threshold, they will open in a cascade; manufacturing tolerance causes members of the array to trip earlier than others, and the remaining PTC fuses will quickly trip in succession.