Solid conductors in raceways
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GEORe: Solid conductors in raceways
the reason for using stranded conductor wiring over solid conductor wiring is due to the way electrons move in conductors.
electrons tend to move more around the outside of the wire and less in the center of the wire. this is known as the "skin effect".
by using stranded wire, we have a more uniform distribution of electron flow throughout the entire wire (less heat generated).
hope this helps.
the reason for using stranded conductor wiring over solid conductor wiring is due to the way electrons move in conductors.
electrons tend to move more around the outside of the wire and less in the center of the wire. this is known as the "skin effect".
by using stranded wire, we have a more uniform distribution of electron flow throughout the entire wire (less heat generated).
hope this helps.
Len_B
Member
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- New Hampshire
Re: Solid conductors in raceways
I think the requirement for #8 and larger to be stranded is simply for mechanical reasons. Flexibility, bending radius, pulling ability, termination, and others are all factors. IMO, I don't think skin effect has much to due with it, especially at lower voltages (wire rated <600v). Note that solid busbars are regularly used at very high voltages in switchyards, etc.
Len
I think the requirement for #8 and larger to be stranded is simply for mechanical reasons. Flexibility, bending radius, pulling ability, termination, and others are all factors. IMO, I don't think skin effect has much to due with it, especially at lower voltages (wire rated <600v). Note that solid busbars are regularly used at very high voltages in switchyards, etc.
Len
alex winkler
Member
Re: Solid conductors in raceways
Al,
I don’t believe 310.3 applies to grounding electrode conductors. In the scope of Article 310 (310.1) it says these requirements do not apply to conductors specifically provided for elsewhere in the code.
In 250.62 it gives grounding electrode conductor material and lists solid or stranded. 250.64 (A) – (F) gives installation instruction. I did not find any restrictions on the size of a solid conductor in a raceway.
Al,
I don’t believe 310.3 applies to grounding electrode conductors. In the scope of Article 310 (310.1) it says these requirements do not apply to conductors specifically provided for elsewhere in the code.
In 250.62 it gives grounding electrode conductor material and lists solid or stranded. 250.64 (A) – (F) gives installation instruction. I did not find any restrictions on the size of a solid conductor in a raceway.
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- PE (Retired) - Power Systems
Re: Solid conductors in raceways
Major misconception alert.
Skin effect is a phenomona of frequency and diameter. At 60hz skin effect does not begin to be a factor until roughly 266kcmil.
Stranding has negligble effect on current carrying capacity. Notice how the NEC does not list ampacities based on stranded vs. solid?
Stranding is done simply to make cable easier to handle, similar to the way flex conduit is easier to handle than EMT.
Major misconception alert.
Skin effect is a phenomona of frequency and diameter. At 60hz skin effect does not begin to be a factor until roughly 266kcmil.
Stranding has negligble effect on current carrying capacity. Notice how the NEC does not list ampacities based on stranded vs. solid?
Stranding is done simply to make cable easier to handle, similar to the way flex conduit is easier to handle than EMT.
luke warmwater
Senior Member
Re: Solid conductors in raceways
I've heard 2 different views on skin effect.
1). The inside conductors are really useless as far as carrying current in stranded wire because current travels on the outside strands.
2). Current travels on the outside of each strand in stranded wire.
It always made more scense to me that #2 would be correct. I'm with you Jim.
I've heard 2 different views on skin effect.
1). The inside conductors are really useless as far as carrying current in stranded wire because current travels on the outside strands.
2). Current travels on the outside of each strand in stranded wire.
It always made more scense to me that #2 would be correct. I'm with you Jim.
dellphinus
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- Southern Illinois, USA
Re: Solid conductors in raceways
Been doing a little digging on skin effect. Seems that most of the info I've found so far says that stranded wire behaves electrically like solid wire unless the strands are individually insulated, so skin effect in solid and stranded would be very similar.
Also, skin effect becomes more of a player as the wire size increases (at a given frequency). At 60 Hz, 12 AWG had slight reduction in conductivity; not much.
I found several pretty good write ups on it, but don't have them here; I'll post them Monday. Simplified calcs for determining skin depth. Also, a description of skin effect's action on a large high current conductor with a "knife nick" from stripping insulation in a circular manner.
Edit: found the info, I'll post it under engineering
[ February 28, 2003, 10:36 PM: Message edited by: dellphinus ]
Been doing a little digging on skin effect. Seems that most of the info I've found so far says that stranded wire behaves electrically like solid wire unless the strands are individually insulated, so skin effect in solid and stranded would be very similar.
Also, skin effect becomes more of a player as the wire size increases (at a given frequency). At 60 Hz, 12 AWG had slight reduction in conductivity; not much.
I found several pretty good write ups on it, but don't have them here; I'll post them Monday. Simplified calcs for determining skin depth. Also, a description of skin effect's action on a large high current conductor with a "knife nick" from stripping insulation in a circular manner.
Edit: found the info, I'll post it under engineering
[ February 28, 2003, 10:36 PM: Message edited by: dellphinus ]
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