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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