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 Post subject: An Odd Ball
PostPosted: Mon Sep 14, 2009 4:21 am 

Joined: Thu Sep 03, 2009 7:14 am
Posts: 3
Is there anyone here who can help me please,

i have a need to try an calculate the AC single phase Arc energy (230v - 20amps upto 470Amps at 50Hz)
I then need to replicate this "Arc energy" at DC at 220volts

Its a totally different application from switchgear and i know most of you would say its to low however i need to try and model this

thanks

Jas


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PostPosted: Mon Sep 14, 2009 12:12 pm 
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Joined: Sun Aug 16, 2009 8:42 am
Posts: 184
Location: Lawrenceburg KY
:confused:
Sorry, out of my league. Sounds like you need someone with the Canadian or European calculations.


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PostPosted: Tue Sep 15, 2009 5:35 am 

Joined: Thu Sep 03, 2009 7:14 am
Posts: 3
Thanks anyway Martin.

i was wondering if i just used VA's, weather or not this would be representative in getting the idea across that an DC Arc is worse than an AC one.

say for instance we pick up load at 230v 420A 50Hz rms (ignoring vectors fro the time being)

That would be 96.6KVA however if the Arc lasted for 1.5s then 1/50 x1.5 = 0.03.
therefore 96600 x 0.03 = 2.9KVA for the duration of the Arc.

If i did the same test on DC (as the AC is rms so should be equivalent to DC)

230V x 420A = 96.6KVA

However with the Arc lasting a 1.5s this equates to 144.9KVA for the duration of the Arc.

so to get similar values at DC as those in AC
:confused:
2900VA / 1.5 = 1933.3 / 420A = 4.6volts
or / 230v = 8.4Amps
:confused: so i think i need a different approach

( this is assuming that the distance and time it take to close the arc is constant)


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PostPosted: Tue Sep 15, 2009 2:32 pm 
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Joined: Tue Feb 24, 2009 7:05 am
Posts: 252
JPJ wrote:
That would be 96.6KVA however if the Arc lasted for 1.5s then 1/50 x1.5 = 0.03.
therefore 96600 x 0.03 = 2.9KVA for the duration of the Arc.


Why 1/50 x 1.5? That's only 1.5 cycle, quite far from the original 1.5 second...


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PostPosted: Tue Sep 15, 2009 8:55 pm 

Joined: Thu Sep 03, 2009 7:14 am
Posts: 3
Ah! its always better to read a post first :o


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