"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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