Re: cable amp ratings - answers to wrong questions

[Victor Tikhonov <vtikhono@lsil.com>]

Thanks Roger for numbers! This is enough info to do the calc 
and decide.

Gauge 4 will serve my needs well - the voltage drop will be 
less than 2V in absolutely worst case (hardest acceleration) -
280A current on 20 feet of cable.

Victor

Roger Stockton wrote:
> 
> > -----Original Message-----
> > From: Victor Tikhonov [mailto:vtikhono@lsil.com]
> > Sent: May 30, 2002 12:20 PM
> > To: ev@listproc.sjsu.edu
> > Subject: cable amp ratings - answers to wrong questions
> >
> >
> > The trouble with all the current ratings found in these books
> > is that it's pointless.
> 
> [snip]
> 
> > So, who do you think writing these references books?
> 
> The Insulated Cable Engineering Association <http://www.icea.net/> or a
> similar professional organisation, not the hired help at Home Depot
> <GRIN>, helpful though they usually are.
> 
> If you want the exact information you are looking for, you'll probably
> have to browse the ICEA site and purchase the appropriate document.  If
> you are satisfied with information that gives you a reasonable comfort
> factor with using a particular cable somewhat beyond its normal ratings,
> then perhaps the information you can find by searching on "welding
> cable" on General Cable's website is sufficient (look at the technical
> information links associated with any of the products that comes up in
> your search, especially "Installation and Engineering Information").
> 
> For instance, the table of recommended welding cable ampacities is based
> on a 4V drop, 60% duty cycle, and a copper temp of 60C in a 40C ambient.
> With these assumptions in mind:
> 
> #4: 150ft@100A or 100ft@150A
> #2: 250ft@100A or 100ft@200A
> #1: 300ft@100A or 100ft@250A
> 1/0:400ft@100A or 100ft@350A
> 
> (the distance is the maximum total circuit length).  This provides
> information about cable resistance (4V drop in the specified length at
> the specified current) and heating (20C rise in conductor temp at the
> specified current and duty cycle).
> 
> Another table provides ampacity information for 90C conductor temp in a
> 40C ambient for 0-2000V:
> 
>                    Current
> gauge  single conductor  2-conductor
> -----  ----------------  -----------
>  8          83              72
>  6         109              95
>  4         145             127
>  3         167             145
>  2         192             167
>  1         223             191
> 1/0        258             217
> 2/0        298             250
> 3/0        345             286
> 4/0        400             328
> 
> Note that these ampacities are for welding cable with 90C rated
> insulation, and the ampacity correction factors for 90C insulated cable
> is provided as:
> 
>           ampacity
> ambient  correction
> (deg. C)   factor
> -------- ----------
>  10         1.26
>  20         1.18
>  30         1.10
>  40         1.00
>  50         0.90
> 
> Hopefully this information is enough for you to convince yourself if
> what you want to do is likely to be OK or certain to be unsafe.  If not,
> I'm sure you can get the original documents that this info was
> extracted/condensed from through the ICEA... for a price.
> 
> Cheers,
> 
> Roger.