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| Incident Energy - 30A Disconnect https://brainfiller.com/arcflashforum/viewtopic.php?f=4&t=4803 |
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| Author: | Swizzle [ Wed Nov 21, 2018 12:05 pm ] |
| Post subject: | Incident Energy - 30A Disconnect |
Has anyone come across incident energy over 8 cal for a 30A 480V disconnect? |
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| Author: | Jim Phillips (brainfiller) [ Thu Nov 22, 2018 7:53 am ] |
| Post subject: | Re: Incident Energy - 30A Disconnect |
Swizzle wrote: Has anyone come across incident energy over 8 cal for a 30A 480V disconnect? It can happen. Since the arc duration is usually defined by how long it takes an upstream overcurrent device to clear the arcing current, a larger incident energy is often due to a longer clearing time from that device. What device is upstream? Do you have a clearing time from the study result? |
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| Author: | PaulEngr [ Fri Nov 23, 2018 10:12 am ] |
| Post subject: | Re: Incident Energy - 30A Disconnect |
Easier than that if it's fed by one big transformer like say a 1000 kva. |
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| Author: | tish53 [ Mon Nov 26, 2018 8:50 am ] |
| Post subject: | Re: Incident Energy - 30A Disconnect |
we have it happen quite often in our Quarries. When you go 1500 feet of cable to a pump down in the pit the short circuit current goes low and the trip time on the Circuit breaker becomes long. |
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| Author: | ProEE [ Tue Nov 27, 2018 12:57 pm ] |
| Post subject: | Re: Incident Energy - 30A Disconnect |
Typically happens at test switches or switches for power factor correction (or PQ monitoring) that are tapped off the main bus of 480 V switchgear. Why those switches are installed the way they are is another topic.  As many have pointed out, it's what's upstream that matters.
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| Author: | Flash [ Wed Dec 05, 2018 8:50 pm ] |
| Post subject: | Re: Incident Energy - 30A Disconnect |
The question would be more interesting if we discussed the possibility of exceeding 1.2 cal down stream from a 30A or 60A fuse and or breaker. For those that use arc flash software try and get the incident energy above 1.2 cal down stream from a Mersen A6K200R or Buss KTSR200. |
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| Author: | PaulEngr [ Mon Dec 10, 2018 6:58 pm ] |
| Post subject: | Re: Incident Energy - 30A Disconnect |
Flash wrote: The question would be more interesting if we discussed the possibility of exceeding 1.2 cal down stream from a 30A or 60A fuse and or breaker. For those that use arc flash software try and get the incident energy above 1.2 cal down stream from a Mersen A6K200R or Buss KTSR200. That seems to be the case regardless of the make or model of device once you get down below about 150%. |
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