Hey guys,
I was wondering if anyone knows which AWG wire size holds the most current? 2, 10, 18, or none of them because AWG number does not directly affect the current-carrying capacity???
Cheers
AWG wire size
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av8tor_assrope
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AWG wire size
I want to die like my grandfather did, peacefully in his sleep. Not screaming in terror like his passengers...
small nit:
The larger the cross-section of metal in the conductor (ie the lower the number) the more current the wire can carry.
The thicker the insulator around the conductor, the more voltage the wire can carry.
Insulation weighs less than metal, which is why you can see 24VDC systems are so popular - you get double the wattage with pretty much the same weight.
Cars are going away from 12VDC for the same reason.
The larger the cross-section of metal in the conductor (ie the lower the number) the more current the wire can carry.
The thicker the insulator around the conductor, the more voltage the wire can carry.
Insulation weighs less than metal, which is why you can see 24VDC systems are so popular - you get double the wattage with pretty much the same weight.
Cars are going away from 12VDC for the same reason.
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av8tor_assrope
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G.N. Thompson
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see below...
GNT
GNT
Last edited by G.N. Thompson on Fri Feb 23, 2007 12:00 pm, edited 1 time in total.
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G.N. Thompson
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From old electrical code book for buildings, if not more than 3 current carrying conductors with insulation rated at 60 degrees C in a cable or raceway:
-#18AWG good for 5 amps
-#16AWG good for 7 amps
-#10AWG good for 30 amps
-# 6AWG good for 60 amps
-# 2AWG good for 100 amps
Current would have to be reduced if ambient temperature above 30 C, or conduit more than 40% full. Higher temperature ratings on the insulation allow higher currents.
If this is for 3 wire service entrance for 120/208 or 240 volt panel then this book allowed 60 amps on #6 and 200 amps on #2/0 (not #2)
Not sure what you are wiring?
GNT
-#18AWG good for 5 amps
-#16AWG good for 7 amps
-#10AWG good for 30 amps
-# 6AWG good for 60 amps
-# 2AWG good for 100 amps
Current would have to be reduced if ambient temperature above 30 C, or conduit more than 40% full. Higher temperature ratings on the insulation allow higher currents.
If this is for 3 wire service entrance for 120/208 or 240 volt panel then this book allowed 60 amps on #6 and 200 amps on #2/0 (not #2)
Not sure what you are wiring?
GNT
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G.N. Thompson
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Negative...CE code discusses every wire application in buildings but stranded versus solid usually only changes the price, not the current.
Curious now...what are the current ratings on those sizes in 7 strand or more in aviation?? What temperature rating does the insulation have to be? Is that specific to each manufacturer...MD11??
GNT
Curious now...what are the current ratings on those sizes in 7 strand or more in aviation?? What temperature rating does the insulation have to be? Is that specific to each manufacturer...MD11??
GNT
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G.N. Thompson
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Wotter,
Please post examples from aviation manuals.
Fairly sure AWG dictates same current whether solid or stranded but it's much harder to get cheaper solid ones in without damage...likely that stranded will also take cold and vibration better too
The last thing we need here is to mislead someone into overloading some wire.
GNT
Please post examples from aviation manuals.
Fairly sure AWG dictates same current whether solid or stranded but it's much harder to get cheaper solid ones in without damage...likely that stranded will also take cold and vibration better too
The last thing we need here is to mislead someone into overloading some wire.
GNT
First off, get my name right if you want me to post..G.N. Thompson wrote:Wotter,
Please post examples from aviation manuals.
Fairly sure AWG dictates same current whether solid or stranded but it's much harder to get cheaper solid ones in without damage...likely that stranded will also take cold and vibration better too
The last thing we need here is to mislead someone into overloading some wire.
GNT
Second off, you are wrong.. I don't think you will find many aviation manuals that have any reference to solid wire.. I've only been in the industry for 32 years and have never seen an example of it..
Remember your last statement about misleading when you think about this.. BTW, AWG has nothing to do with what current a wire will carry, it only has to do with size.. Are you trying to say that an aluminum wire of say 12 AWG will carry the same load as a copper one?? Check that out!!
There is very little difference between stranded and solid wires with respect to their current carrying capabilities unless you are using it in a high frequency application. They you have to worry about "skin effect".Those #'s are for solid wire, where if you use stranded wire as we do in aviation your capacity will be larger for the size of wire.
http://en.wikipedia.org/wiki/Skin_effect
For frequencies encountered in typical airplane wiring, skin effect isn't critical.
The numbers expressed by G.N. Thompson for the solid wire are limited by the insulation rating and not by the gauge. Therefore its incorrect to state that stranded wire used in "aviation" has a larger capacity because its stranded.
Typical aircraft wire carries more current because the insulation temperature rating are usually higher. 150C or 200C are common ratings. (See AC 43.13 chapter 11)
http://www.airweb.faa.gov/Regulatory_an ... r%2011.pdf
The original question asked which wire would carry more current. The American Wire Gauge (AWG) is usually used and the larger numbers represent smaller wire. The gauge represents how many wires can be put side by side to span 1 inch. This original gauging format works for the smaller gauges but isn't consistent with the larger ones.
So which one carries more current? It depends on other factors as well. AC 43 contains guidelines in selecting wires. The properties we must examine include;
1. Gauge
2. Conductor material
3. Insulator material
4. Insulator thickness
5. Wire length
Lower gauge (larger) wires (of the same type) carry more current than higher gauge wires because there is less resistance and subsequently less voltage drop along the wire.
Copper wire can carry more current than Aluminum, again for similar reasons. Aluminum has higher resistance and an extra disadvantage in that it is dissimilar to copper. Extra care must be taken when connecting aluminum wires to copper (or copper alloy) connections to avoid galvanic corrosion.
http://en.wikipedia.org/wiki/Galvanic_corrosion
The insulator type is the main consideration in determining the temperature rating of the wire. PVC (which is restricted in aircraft but prevalent in house wiring) is generally low temperature. Teflon and formulations more common in aircraft allow for hotter wire operating temperatures. Kapton, which is also restricted in aircraft these days has similar high temperature properties.
The thickness of the insulation used along with the material type determine the dielectric (insulating) properties which in turn determines the maximum voltage range.
The wire length is a factor as well because longer wires have a higher total resistance and a resulting higher voltage drop.
So, using the generally accepted guidelines, for the same type of wire, the smaller gauge wire will carry the most current. However using the guidance in AC 43.13 chapter 11, a long length of aluminum 18 AWG wire with a 150C temperature rating may not be capable of carrying more current than a sort length of copper AWG 22 wire with a 260C temperature rating.
28 VDC systems do in fact save weight because systems that operate at higher voltages draw less current and can therefore use higher gauge wire. The increase in voltage doesn’t however normally result in thicker insulation. Wire that is suitable for 14 volts is normally suitable for 28 volts.
The more popular aircraft wires are generally rated to 600 volts. No need to thicken the insulation to raise the voltage to 28.
Generally speaking, wire in airplanes is restricted to 19 stands or more. The widely accepted wiring standards are contained in AC 43.13. Many larger aircraft publish their own wiring standard practices where they prescribe wire type, repairs, routing, etc.Curious now...what are the current ratings on those sizes in 7 strand or more in aviation?? What temperature rating does the insulation have to be? Is that specific to each manufacturer...MD11??
The type of wire acceptable for use on any one airframe varies and is based primarily on the certification basis of the airplane. Newer airplanes usually have more stringent wire flammability standards than older airplanes.
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ragbagflyer
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Calm down Twotter (did I get your name right).twotter wrote:Methinks you are wrong regarding stranded vs solid. Electricity travels on the outside of wire, stranded gives more area and therefore more capacity.
First off, as CID has just posted, the fact that under some conditions more current will travel on the outside of a conductor doesn't really apply here. If we're talking airplanes then we're probably mostly concerned with DC, and skin effect applies to AC in really high frequency applications, not the 60 Hz most of us deal with day to day.
Secondly, AWG is a measure of wire size, but if you look at the specs regarding diameter you'll find that it's based on solid wire benchmark. As far as ampacity, all other things being equal, larger wire equals higher capacity. "Larger" refers to cross sectional area, not surface area. As an example, say a 10 AWG solid wire has a cross sectional copper area of "X" , and a diameter of "Y". Along comes a 10 AWG stranded wire, it will have the same cross sectional area of "X" but because it's stranded, it will actually have a slightly larger diameter. I stress slightly. But to rebut your previous statement, No, stranded wire won't have a higher ampacity then it's solid counterpart. Infact, theoretically, if you made two conductors, one solid and one stranded, that had EXACTLY the same diameter, the solid conductor would have a greater cross sectional area and therefore, with all other variables (insulation, temp, voltage and distance) being equal, a greater ampacity.
An additional factor that can apply is if the wire is "tinned" or not. Some aviation copper wire is coated with if I recall correctly silver? Which has a higher conductance than copper. From my understanding stranded wire is used in aviation because of its resistance to mechanical damage from vibration and ability to pass around a smaller radius of turn for istallation and routing.
Copper wire is usually coated or "tinned" with various coatings because copper is fairly reactive with oxygen and corrodes easily. Corrosion is accelerated in the presence of water and/or heat.
The larger solid copper used in house wiring doesn't suffer so badly because of the thickness of the single strand The corrosion tends to penetrate a certain thickness and stop. Very small gauges of solid copper are typically coated for the same reasons small strands are.
Stranded wire uses very tiny strands therefore the corrosion layer can penetrate a much larger percentage of the total diameter of each strand.
Most stranded copper aircraft wire is coated with tin, nickel or silver. Out of those three silver has the best anti-corrosion properties but is obviously more expensive. Copper is used extensively as the main wire material because it strikes a very good balance between conductivity and corrosion resistance.
Aluminum wire is not normally coated because aluminum actually exhibits good corrosion properties. Aluminum reacts quite readily with oxygen but the corrosion layer isn’t very thick and it creates a tough oxide barrier to subsequent exposure to oxygen.
There has been some discussion on the cross sectional area of wire and the differences between stranded and solid wires.
Stranded wires actually have a little less cross sectional area due to the spaces between the strands. This is mitigated by the manufacturing process that “squashes” the wires together. If you take a stranded wire apart and look at the individual strands, you’ll often see that they are not perfectly circular.
For the purposes of determining current handling, the difference between solid and stranded wire is negligible.
The larger solid copper used in house wiring doesn't suffer so badly because of the thickness of the single strand The corrosion tends to penetrate a certain thickness and stop. Very small gauges of solid copper are typically coated for the same reasons small strands are.
Stranded wire uses very tiny strands therefore the corrosion layer can penetrate a much larger percentage of the total diameter of each strand.
Most stranded copper aircraft wire is coated with tin, nickel or silver. Out of those three silver has the best anti-corrosion properties but is obviously more expensive. Copper is used extensively as the main wire material because it strikes a very good balance between conductivity and corrosion resistance.
Aluminum wire is not normally coated because aluminum actually exhibits good corrosion properties. Aluminum reacts quite readily with oxygen but the corrosion layer isn’t very thick and it creates a tough oxide barrier to subsequent exposure to oxygen.
There has been some discussion on the cross sectional area of wire and the differences between stranded and solid wires.
Stranded wires actually have a little less cross sectional area due to the spaces between the strands. This is mitigated by the manufacturing process that “squashes” the wires together. If you take a stranded wire apart and look at the individual strands, you’ll often see that they are not perfectly circular.
For the purposes of determining current handling, the difference between solid and stranded wire is negligible.
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G.N. Thompson
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Thank you CID, that does help.
I have not been tempted to use aluminum on anything after reading about
"cold flow"...it gets loose under pressure in connectors or under a screw.
And a word about voltage drop...I think a purely resistive load such as lamps or heaters would see less voltage on a long wire and draw less current. But transformers or motors will see low voltage and draw more current trying to produce designed horsepower...feller has to allow for that usually by using larger wire.
See now that derating neutral wires, believing they only carried the "Unbalanced load" in 3 phase systems, was another bad idea...turns out impedence of transforemer (2piFL) changes big time when harmonics from SCR type power supplys change the frequency. Using better instruments they have measured up to 7 times the conductor current in the neutral...which explained the odd smoked building.
GNT
I have not been tempted to use aluminum on anything after reading about
"cold flow"...it gets loose under pressure in connectors or under a screw.
And a word about voltage drop...I think a purely resistive load such as lamps or heaters would see less voltage on a long wire and draw less current. But transformers or motors will see low voltage and draw more current trying to produce designed horsepower...feller has to allow for that usually by using larger wire.
See now that derating neutral wires, believing they only carried the "Unbalanced load" in 3 phase systems, was another bad idea...turns out impedence of transforemer (2piFL) changes big time when harmonics from SCR type power supplys change the frequency. Using better instruments they have measured up to 7 times the conductor current in the neutral...which explained the odd smoked building.
GNT
AC is used in many large aircraft to simply the distribution of electrical power. It is sometines arguable if it decreases weight since in some airplanes, heavy constant speed drives (CSD) and Transformer Rectifier Units (TRU) are required to produce the proper voltages and frequencies. All this added weight sometimes offsets much of the weight reduced by using smaller wires.
Furthermore, there is a limit to how small you want your wires to be so some very low current circuits end up using a wire many times larger than the load requires. For example, at 115 VAC, a 100 watt load would only need about a 1 amp supply however you rarely see wires smaller than 24 AWG on power distribution circuits.
New technology has helped a bit. Some airplanes use wild frequency generators and high efficiency frequency and voltage converters and equipment that is compatible with 115 VAC wild frequncy which helps to eliminate the heavy CSDs and TRUs.
Systems on airplanes typically use the neutral return wire on three phase "wye" system to sense phase imblance, shutting down the suspected load or generator. I don't know of any system on aircraft that uses the neutral wire as an alternate return line.
With respect to voltage drop, for resistive loads, AC acts like DC when you consider the transmission lengths are short.
For loads that have capacitive or inductive elements, voltage and current phase shifts. The degree it shifts depends on the amount of DC resistance and AC resistance. (often called impedance)
I don't think a detailed discussion about this topic is warranted here but its good to understand that when you're talking about loads like motors, the total power consumed is not the simple product of the volts and amps like it is for purely resistive circuits. The phase shift between voltage and current reduces the "real" power consumed by the load by it's "power factor" which is the cosine of the phase difference.
So a motor with a power factor of 0.8 on a 115VAC system drawing 2 amps will consume 184 watts of real power but if you just measure the volts and amps and don't consider the reactive load, you'll think its pulling 230 watts.
Furthermore, there is a limit to how small you want your wires to be so some very low current circuits end up using a wire many times larger than the load requires. For example, at 115 VAC, a 100 watt load would only need about a 1 amp supply however you rarely see wires smaller than 24 AWG on power distribution circuits.
New technology has helped a bit. Some airplanes use wild frequency generators and high efficiency frequency and voltage converters and equipment that is compatible with 115 VAC wild frequncy which helps to eliminate the heavy CSDs and TRUs.
Systems on airplanes typically use the neutral return wire on three phase "wye" system to sense phase imblance, shutting down the suspected load or generator. I don't know of any system on aircraft that uses the neutral wire as an alternate return line.
With respect to voltage drop, for resistive loads, AC acts like DC when you consider the transmission lengths are short.
For loads that have capacitive or inductive elements, voltage and current phase shifts. The degree it shifts depends on the amount of DC resistance and AC resistance. (often called impedance)
I don't think a detailed discussion about this topic is warranted here but its good to understand that when you're talking about loads like motors, the total power consumed is not the simple product of the volts and amps like it is for purely resistive circuits. The phase shift between voltage and current reduces the "real" power consumed by the load by it's "power factor" which is the cosine of the phase difference.
So a motor with a power factor of 0.8 on a 115VAC system drawing 2 amps will consume 184 watts of real power but if you just measure the volts and amps and don't consider the reactive load, you'll think its pulling 230 watts.
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G.N. Thompson
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CID,
Thank you. I'm thinking it actually is 'pulling' that power from the source...but you would be right so say actual work you get out of it would be measured in watts and would be .8 of volts times amps seen going in...therefore again we should not go cheap on the wire, and should keep in mind locked rotor (stalled) motor current can be like 8 times the full load current of the motor. This can make big smoke.
Twotter,
Thank you too, appears that same current usually requires bigger wire if using aluminum.
I'm thinking impedence of transformers designed for 400 Hz would also change if harmonics introduced. I'm no expert on this but will guess that these stray frequencies could show up on both sides of the transformer??
GNT
Thank you. I'm thinking it actually is 'pulling' that power from the source...but you would be right so say actual work you get out of it would be measured in watts and would be .8 of volts times amps seen going in...therefore again we should not go cheap on the wire, and should keep in mind locked rotor (stalled) motor current can be like 8 times the full load current of the motor. This can make big smoke.
Twotter,
Thank you too, appears that same current usually requires bigger wire if using aluminum.
I'm thinking impedence of transformers designed for 400 Hz would also change if harmonics introduced. I'm no expert on this but will guess that these stray frequencies could show up on both sides of the transformer??
GNT
There are alot of different topics being dragged in to this discussion on wire gauge.
Some loads like motor loads and lamp loads exhibit large "inrush" currents. Motors generate their own "back voltage" as they turn which opposes the supply voltage and reduces the current draw.
Light bulbs are typically made using a tungsten filarment that is quite low in resistance when cold, but higher when heated by the current flowing through it.
Wire and supply components to these types of loads need to be rated higher then an equivalent pure DC load. The generally accepted derating factor for lamp loads is 8. So for a light bulb that draws 1 Amp, switches and other ciruit components should be rated for at least 8 Amps.
There are other rating factors for inductive loads etc. (See AC 43.13)
Locked motors continuously draw their peak inrush current. Large motors usually have protection against long term inrush currents. Industrial (non aviation) motors require such devices as well. The lowest tech form uses motor "heaters". These are thermal devices that open when large currents are passed for extended periods. Much like a thermal circuit breaker.
As for transformers used in power distribution in aircraft, there is no major black magic there. 400 Hz is used because the devices can be smaller. Its a low enough frequency and the waveforms are generally clean enough that we don't have to worry about factors such as high speed switching or harmonics.
Some loads like motor loads and lamp loads exhibit large "inrush" currents. Motors generate their own "back voltage" as they turn which opposes the supply voltage and reduces the current draw.
Light bulbs are typically made using a tungsten filarment that is quite low in resistance when cold, but higher when heated by the current flowing through it.
Wire and supply components to these types of loads need to be rated higher then an equivalent pure DC load. The generally accepted derating factor for lamp loads is 8. So for a light bulb that draws 1 Amp, switches and other ciruit components should be rated for at least 8 Amps.
There are other rating factors for inductive loads etc. (See AC 43.13)
Locked motors continuously draw their peak inrush current. Large motors usually have protection against long term inrush currents. Industrial (non aviation) motors require such devices as well. The lowest tech form uses motor "heaters". These are thermal devices that open when large currents are passed for extended periods. Much like a thermal circuit breaker.
As for transformers used in power distribution in aircraft, there is no major black magic there. 400 Hz is used because the devices can be smaller. Its a low enough frequency and the waveforms are generally clean enough that we don't have to worry about factors such as high speed switching or harmonics.
