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| NFPA 70E D.8.1.1 DC Arc Flash https://brainfiller.com/arcflashforum/viewtopic.php?f=7&t=2520 |
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| Author: | Peter Lewis [ Mon Nov 05, 2012 4:02 pm ] |
| Post subject: | NFPA 70E D.8.1.1 DC Arc Flash |
Looking at the equation given in D.8.1.1 (IEm=0.01*Vsys*Iarc*Tarc/D^2), the units are Volts*Amps*Time/area^2. Volts*Amps = Watts Watts*Seconds = Joules It seems like the answer should be in J/cm^2, not in Cal/cm^2 as noted. That difference is 1 Joule = 0.239 calories. Am I missing something? Seems like the result given is 4.187 times higher than it should be. |
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| Author: | Vincent B. [ Tue Nov 06, 2012 6:49 am ] |
| Post subject: | |
The answer lies in the 0.01 magic constant in front. You don't see 1/Pi, you don't see 1/4, you don't see the other 1/2, you don't see 1/4.187. Everything is hidden in 0.01. Gotta love those Handbook style equations... |
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