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 Post subject: Time –Current Curves for Low Voltage Fuses
PostPosted: Mon Feb 16, 2015 1:05 am 
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Joined: Sun Jul 22, 2007 5:00 pm
Posts: 27
Location: Stratham, SW Australia
Time –Current Curves for Low Voltage ( =< 1000V a.c. ) Industrial Fuselinks
Fuse manufacturers such as GEC ( IPD ) type T fuselinks to BS88 publish time-current curves for the average pre-arc time ( melt time ) as a function of symmetrical rms current.

IEEE1584-2002 Section 4.6 Step 5 states :

For fuses, the manufacturer’s time-current curves may include both melting and clearing time. If so, use the
clearing time. If they show only the average melt time, add to that time 15%, up to 0.03 seconds, and 10%
above 0.03 seconds to determine total clearing time. If the arcing fault current is above the total clearing time
at the bottom of the curve (0.01 seconds), use 0.01 seconds for the time.

Question 1.
Is the fuse total clearing time ( pre-arcing plus arcing time ) :
- For t =< 0.03 sec Total clearing time = average pre-arcing time + 1.15 * average pre-arcing time.
- For t > 0.03 sec Total clearing time = average pre-arcing time + 1.10 * average pre-arcing time.

Question 2.
Would it be realistic to assume a minus 10% time tolerance for the pre-arcing time-current curve ?


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