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Re: fusing current of wires

Subject: 
            Re: fusing current of wires
       Date: 
            Wed, 09 Apr 1997 08:59:39 -0700
       From: 
            Skip Greiner <sgreiner-at-wwnet-dot-com>
Organization: 
            Greiner, Ltd.
         To: 
            Tesla List <tesla-at-pupman-dot-com>
 References: 
            1


Tesla List wrote:
> 
> Subject:
>         fusing current of wires
>   Date:
>         Tue, 8 Apr 97 11:05:16 EDT
>   From:
>         pierson-at-gone.ENET.dec-dot-com
>     To:
> 
> mail11:;;;;;-at-us4rmc.pko.dec-dot-com-at-us4rmc.pko.dec-dot-com-at-unknown.pupman-dot-com;;;;;;;;
> (-at-teslatech)
>     CC:
>         pierson-at-gone.ENET.dec-dot-com
> 
> >> > Fr. MaGahee: At one time you mentioned that you thought these
> >> > transformers have large wire in the secondaries. Do you know what size
> >> > it is?
> 
> >> I fried one of my transformers, so I did a dissection.  I estimated the
> >> wire at about a #28 gauge.
> 
> >I finally got into one of the secondaries. The wire measures 0.010"
> >which is #30. According to the ARRL handbook this wire is capable of
> >about 140ma using standard design criteria. I am still very afraid of
> >drawing 300ma but will go ahead with tests.
> 
> >Skip
>         Standard Handbook for Electrical Engineers list three different
>         formulas for fusing current.  The simplest is
> 
>         I=Ad**(3/2)
> 
>         d is in inches.
>         A is a constant:
>                 10,244 for Copper.
>                 7,585 for Aluminum.
> 
>         Tho they say it has limitations.
> 
>         (the others get seriously complex for typing...)
>         (I haven't run any numbers....)
> 
>         Eleswhere they have a chart, which shows
>                 #30 at 10A for 2 seconds
>                 #28 at 10A for 5 seconds
>         Eyballing off the end of the chart #30 might carry an amp
>         'indefinitely....'
> 
>         (For comparison #14, UL/NFPA fused for 14A for house wiring,
>         is 120A, for 10 seconds...   8)>>.  (the chart only extends to
>         10 seconds....))
> 
>         regards
>         dwp

Hi DWP

Thanks for the input. I still approach these trannies with a certain
amount of trepidation. They are cheaply made which might mean that the
winding machines were not well adjusted. This obviously leads to
stretched wire and in the case of #28 or #30 this could represent real
problems when trying to push the wire to its capabilities. Anyway I plan
to go ahead and PUSH.

Skip