Hi Tom,
"The cord connected concept works fine as long as you are using a predicted
path and can prevent damage to the cord."
Indeed, and both conditions are met in an agricultural context... not so for
your average car tho! Perhaps layering the cord, rather than coiling would
work better...?
MW
On 23 Feb 2014, at 23:23, Thos True wrote:
> Yes, there are many large cord connected pieces of electric machinery in
> use these days! I had the pleasure of being on the build crew of Bertha,
> the world's largest tunnel boring machine (57' cut, powered with a long
> extension cord). It runs on 26K, and the cord will eventually be over 2
> miles long!
> The cord connected concept works fine as long as you are using a predicted
> path and can prevent damage to the cord.
>
> -Tom
>
>
> On Sun, Feb 23, 2014 at 2:58 PM, Michael Ross <michael.e.r...@gmail.com>wrote:
>
>> Aside from the resistive heating, if you have a coil and pass an
>> oscillating current though it a vibrating field is created which will
>> interact with any conductor sufficiently close to it - including itself.
>> Each "line for flux" creates an eddy in a conductive material it
>> intersects, like little tiny motors inside the material each line as it
>> rises and falls has a resulting tiny circular current around it - an eddy.
>>
>> All this depends on the AC nature. DC current does not cause this after
>> its first rise, after switching. A regularly switched DC has the same
>> inductive effects as continuous AC.
>>
>> If you pass AC in two directions along parallel wires, there is a
>> possibility they will cancel - but also a possibility they do not. I doubt
>> the cancellation is perfect. Is the magnitude great? I don't know. The
>> third conductor is presumably a ground in DC? It will have eddies in it.
>> In three phase AC where each phase is out from the others is ther any
>> cancellation of inductive effects? I don't know. I am a lowly ME.
>>
>> It is worth noting that frequency of oscillation is very important and
>> material specific.
>>
>>
>> On Sun, Feb 23, 2014 at 10:22 AM, Evan Tuer <evan.t...@gmail.com> wrote:
>>
>>> Because there's current flowing through a resistance, producing heat.
>>> Normally it's fine, the few Watts per metre lost as heat are easily
>>> conducted away from the wire. If you bundle lots of cable (therefore
>> lots
>>> of Watts) into a small space, the temperature can build up until the wire
>>> insulation melts.
>>>
>>> Makes no difference whether it's AC or DC.
>>>
>>>
>>> On Sun, Feb 23, 2014 at 8:24 PM, Martin WINLOW <m...@winlow.co.uk> wrote:
>>>
>>>> "three conductor wire" - Do you mean 3-phase?
>>>>
>>>> Why do ordinary domestic AC mains cable reels heat up if used coiled,
>>>> then? MW
>>>>
>>>>
>>>> On 22 Feb 2014, at 17:26, Bill Dube wrote:
>>>>
>>>>> AC, not DC powered. Transformer changes ~13 kv distribution voltage
>>> down
>>>> to 480 vac.
>>>>>
>>>>> Cord reels ("coils") consist of three conductor wire with current
>>>> flowing equally in both directions, so there is no inductance
>> associated
>>>> with the "coil". Thus no inductive heating from the AC.
>>>>>
>>>>> On 2/22/2014 3:55 AM, Martin WINLOW wrote:
>>>>>> Hi Bill,
>>>>>>
>>>>>> I'm assuming the power must be DC... or otherwise wouldn't the coils
>>>> get V hot? Or is this what the transformer you mentioned deals with?
>>>>>>
>>>>>> MW
>>>>>>
>>>>>>
>>>>>> On 21 Feb 2014, at 17:53, Bill Dube wrote:
>>>>>>
>>>>>>> Electric coal mining equipment is cord-connected. Even enormous
>>>> draglines ("steam" shovels on steroids) are typically cord connected
>> with
>>>> 13 kV cables. It is a mature science. Coal mining equipment has been
>>>> electric powered since the early 1900's. Specialized cables, reels,
>>>> transformers, and equipment for the mining industry. Easily
>> transferable
>>>> technology to agriculture.
>>>>>>>
>>>>>>> They typically put a reel on the back of the mining machine that
>> pays
>>>> out (or pulls in) the cable as needed. They have a "load center"
>>>> transformer that is moved around as the mining process proceeds.
>>>>>>>
>>>>>>> Electric shuttle car for underground coal transport from working
>>> face:
>>>>>>> http://www.undergroundcoal.com.au/fundamentals/11_face.aspx
>>>>>>>
>>>>>>> Nifty tutorial on cables for mining EVs:
>>>>>>> http://www.cdc.gov/niosh/mining/content/deratingfactors.html
>>>>>>>
>>>>>>> Dragline cable:
>>>>>>>
>>>>
>>>
>> http://www.miningphoto.com/details/2140/dragline_working_in_background_removing_overburden_with_drill_rigs_drilling_blas
>>>>>>>
>>>>>>> Bill Dube'
>>>>>>> (Used to work as an Electrical Inspection intern for the Mine
>> Safety
>>>> and Health Administration, MSHA)
>>>>
>>>> _______________________________________________
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>>
>>
>> --
>> Put this question to yourself: should I use everyone else to attain
>> happiness, or should I help others gain happiness?
>> *Dalai Lama *
>>
>> Tell me what it is you plan to do
>> With your one wild and precious life?
>> Mary Oliver, "The summer day."
>>
>> To invent, you need a good imagination and a pile of junk.
>> Thomas A. Edison<
>> http://www.brainyquote.com/quotes/quotes/t/thomasaed125362.html>
>>
>> A public-opinion poll is no substitute for thought.
>> *Warren Buffet*
>>
>> Michael E. Ross
>> (919) 550-2430 Land
>> (919) 576-0824 <https://www.google.com/voice/b/0?pli=1#phones> Google
>> Phone
>> (919) 631-1451 Cell
>> (919) 513-0418 Desk
>>
>> michael.e.r...@gmail.com
>> <michael.e.r...@gmail.com>
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>>
>>
>
>
> --
> Remember, it is not that the glass is half empty, in reality, the glass is
> merely twice the size that it needs to be! -TNT'82
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