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From: Paul Burridge
Subject: Re: PCB Current capacity??
X-Newsreader: Forte Agent 1.8/32.548
Date: Tue, 21 Jan 2003 07:33:26 +0000
NNTP-Posting-Date: Tue, 21 Jan 2003 10:30:55 GMT
Organization: Virgin Net Usenet Service
On Sun, 19 Jan 2003 23:38:57 GMT, "DG_1"
>> about 25-30Amps. Can a PCB do that??
>Sure it can. Here is how to calculate the PCB
>I = k * T^0.44 * A^0.725
>I = max. trace current
>k = derating constant (.024 for inner layer, 0.48 for outer)
>T = maximum temperature rise above ambient (in deg. C)
>A = cross sectional area in square mils
> as a product TW*CW where TW is trace width in mils
> and CW is coper wight in oz. (1oz = 1.44 mils)
I came across this piece in Radio Communication (at section 17.21):
"Avoid high current density points. Rapid changes of line width should
be avoided, particularly in circuits carrying several amps. The
recommended current density "I" in amps is:
I = 3(cube root of w^2)
where "w" is the width of the copper track in mm.
Circuit board tracks make excellent fuses if poorly designed."
"What is now proved was once only imagin'd"
- William Blake, 1793
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