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AG
Joined: 17 May 2001
Posts: 34
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 20 Feb 2003 12:37 PCB FUSE |
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| How can calculate FUSE on PCB TRACE ?
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House_Cat
Joined: 21 Feb 2002
Posts: 1349
Helped: 274
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| 20 Feb 2003 21:46 |
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Look at the following paper:
h**p://www.ultracad.com/fusing.pdf
(substitute t for * above)
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Phil woz ere
Joined: 12 Feb 2002
Posts: 136
Helped: 2
Location: UK
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| 21 Feb 2003 0:12 Re: PCB FUSE |
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| AG wrote: |
| How can calculate FUSE on PCB TRACE ? |
Forget it they are not accurate enough.
Phil 
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flatulent
Joined: 19 Jul 2002
Posts: 4856
Helped: 292
Location: Middle Earth
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| 21 Feb 2003 3:29 amplify |
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To amplify upon Phil's remarks, there are two problems. Th first is the uncertainty of the heat conduction away from the trace. The other is the manufacturing tolerances for very narrow traces.
You would be better off with a soldered in fuse.
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jzo777n
Joined: 10 Sep 2002
Posts: 113
Helped: 2
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| 21 Feb 2003 7:58 |
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I think that you also have problem with wider traces because the PCB manufacture has to guarantee a minimum thickness and has generous maximum tolerance.
I check this once when I was doing a shunt resistor for current measurement and got the response that the tolerance was something like –0% and +50% on the thickness.
jzo
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ted
Joined: 12 Mar 2002
Posts: 118
Helped: 3
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| 21 Feb 2003 19:04 |
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IMHO pcb trace can be used as a fuse, if the requirements are not very precise. In other words, diffrence between operating current and fault current are very wide, and the purpose is primarly to prevent fire than protect some other components. For instance it mightbe good enough in a car environment, where the battery for sure delivers plenty of current in case of a short circuit, and while the load to be protected is something simple with quite predictable failure modes (short to chassis or similar).
One big trouble is that the PCB is seriously damaged when the fuse blows.
I would in most cases recommend a pcb solderable chip fuse, or other well specified "real" fuse.
Btw. be aware that the specification for nominal current can be according to several standards, and they are VERY different! The humble fuse can be a though thing to specify.
Good luck,
Ted
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MCMC
Joined: 02 Feb 2002
Posts: 239
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| 22 Feb 2003 5:06 |
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Hi all
maybe ag need to know what is the melted point of the pcb track
mcmc
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