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 Post subject: Parallel Fuses - Equivalent Time-Current CurvePosted: Sun Jan 22, 2012 6:10 pm

Joined: Sun Jul 22, 2007 5:00 pm
Posts: 35
Location: Stratham, SW Australia
When an arcing fault occurs downstream from two 100A fuses in parallel, can the fuses modelled by a single 100A fuse by shifting the current axis to the right by a factor of two to represent the time-current curve for the two parallel 100A fuses ?
The above assumes that the current divides equally between the two 100A parallel fuses.

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 Post subject: Posted: Mon Jan 23, 2012 10:59 am
 Sparks Level

Joined: Thu Jul 07, 2011 6:03 am
Posts: 70
Location: Netherlands
Yes you can do this, as long as your assumption holds (no difference in cable lengths, same source, etc.). I don't know which software you use, but properly modeled it may already account for the division. The arcing fault is calculated at a bus so it's not immediately obvious that the time is determined with half of it.

When plotting the TCC a 2x multiplier for a single curve will help visualize the device's actual response to an arcing fault. This also makes it easy to visually check if your calculation is correct.

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