2Likessolid core wire resistance
10-30-2018 | 08:13 PM
#1
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Tech Master
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From: Florida
solid core wire resistance
Has anyone tested solid core wiring from an ESC to a motor?
If you do enough reading you will find that quality solid core wire has less resistance than stranded wire of the same AWG. Stranded wire is to resist damage from flexing and that is fundamental just like resistance is fundamental. I have been running milspec single strand cable for 6 months now and see no problems with it yet. The wires dont get hot and resistance hasnt changed. I do have all of the wires supported and mounted to devices that dont move an appreciable amount.
By the way if anyone is looking to measure for small differences in resistance you can get lab grade powersupplies that do voltage and current limiting for less than 50bucks now. A powersupply with a current limit allows you to bridge a circuit together that you want to measure low resistance values on by creating a low current short and measureing the voltage at a current limit to calculate resistance at very small increments of resistance.
Poor mans LCR if you you want to measure motor or wire resistance. Be warned that direct shorts let the smoke out if you pass too much current. Ask someone who knows a ohms law.
by the way do not try this on a semiconductor. Dont even consider unless its on something like a winding or a wire with suitable current limits.
If you do enough reading you will find that quality solid core wire has less resistance than stranded wire of the same AWG. Stranded wire is to resist damage from flexing and that is fundamental just like resistance is fundamental. I have been running milspec single strand cable for 6 months now and see no problems with it yet. The wires dont get hot and resistance hasnt changed. I do have all of the wires supported and mounted to devices that dont move an appreciable amount.
By the way if anyone is looking to measure for small differences in resistance you can get lab grade powersupplies that do voltage and current limiting for less than 50bucks now. A powersupply with a current limit allows you to bridge a circuit together that you want to measure low resistance values on by creating a low current short and measureing the voltage at a current limit to calculate resistance at very small increments of resistance.
Poor mans LCR if you you want to measure motor or wire resistance. Be warned that direct shorts let the smoke out if you pass too much current. Ask someone who knows a ohms law.
by the way do not try this on a semiconductor. Dont even consider unless its on something like a winding or a wire with suitable current limits.
10-30-2018 | 08:34 PM
#2
Has anyone tested solid core wiring from an ESC to a motor?
If you do enough reading you will find that quality solid core wire has less resistance than stranded wire of the same AWG. Stranded wire is to resist damage from flexing and that is fundamental just like resistance is fundamental. I have been running milspec single strand cable for 6 months now and see no problems with it yet. The wires dont get hot and resistance hasnt changed. I do have all of the wires supported and mounted to devices that dont move an appreciable amount.
By the way if anyone is looking to measure for small differences in resistance you can get lab grade powersupplies that do voltage and current limiting for less than 50bucks now. A powersupply with a current limit allows you to bridge a circuit together that you want to measure low resistance values on by creating a low current short and measureing the voltage at a current limit to calculate resistance at very small increments of resistance.
Poor mans LCR if you you want to measure motor or wire resistance. Be warned that direct shorts let the smoke out if you pass too much current. Ask someone who knows a ohms law.
by the way do not try this on a semiconductor. Dont even consider unless its on something like a winding or a wire with suitable current limits.
If you do enough reading you will find that quality solid core wire has less resistance than stranded wire of the same AWG. Stranded wire is to resist damage from flexing and that is fundamental just like resistance is fundamental. I have been running milspec single strand cable for 6 months now and see no problems with it yet. The wires dont get hot and resistance hasnt changed. I do have all of the wires supported and mounted to devices that dont move an appreciable amount.
By the way if anyone is looking to measure for small differences in resistance you can get lab grade powersupplies that do voltage and current limiting for less than 50bucks now. A powersupply with a current limit allows you to bridge a circuit together that you want to measure low resistance values on by creating a low current short and measureing the voltage at a current limit to calculate resistance at very small increments of resistance.
Poor mans LCR if you you want to measure motor or wire resistance. Be warned that direct shorts let the smoke out if you pass too much current. Ask someone who knows a ohms law.
by the way do not try this on a semiconductor. Dont even consider unless its on something like a winding or a wire with suitable current limits.
That really depends. At higher frequencies, the skin effect will mean stranded wire has less impedance. Even though these are DC motors, they switch on and off as the different phases are energised.
10-30-2018 | 11:41 PM
#3
Hey Guys, I have a little experience with this as I had issues before with using stranded audio wire for primary power wire in my car. While the skin effect is true, too many small strands cannot handle the amp draw and will fail and gain resistance. So its a balance between the number of strands and how thick they are.
Based on what your saying Solid wire did not improve your resistance, but I know from personal experience that solid wire is hard to work with in some cases and also it will break over time with the shock of landing etc without the flex.
In no case would I use a solid conductor unless it is permanent wiring like in homes where there is no movement and there is no risk to the wires. Your solid wires are going to transfer allot of vibration to your connections and you could break off a solder tab or something stupid, I do not recommend this. I have seen it happen before, just like the paperclip effect, you bend it too much it breaks. While I am pulling various non rc experiences into this, I am composing a conclusion that solid wire is not going to be good in the long run and serve no advantage now or later, but does introduce risk of breakage that you may not have experienced yet, but when it does could be an expensive breakage.
I think using 10GA stranded wire is fine for RC, but when drawing super high amps on something like a car starter you need to reduce strands and go to higher gauge strands.
Based on what your saying Solid wire did not improve your resistance, but I know from personal experience that solid wire is hard to work with in some cases and also it will break over time with the shock of landing etc without the flex.
In no case would I use a solid conductor unless it is permanent wiring like in homes where there is no movement and there is no risk to the wires. Your solid wires are going to transfer allot of vibration to your connections and you could break off a solder tab or something stupid, I do not recommend this. I have seen it happen before, just like the paperclip effect, you bend it too much it breaks. While I am pulling various non rc experiences into this, I am composing a conclusion that solid wire is not going to be good in the long run and serve no advantage now or later, but does introduce risk of breakage that you may not have experienced yet, but when it does could be an expensive breakage.
I think using 10GA stranded wire is fine for RC, but when drawing super high amps on something like a car starter you need to reduce strands and go to higher gauge strands.
10-31-2018 | 04:57 AM
#4
Tech Master
Joined: Jul 2009
Posts: 1,416
From: Deep South Texas
I can see it being an issue over 20 feet.. but 6 to 8 inches of wire... WHY ?
the high amp draw time involved is in micro seconds... as its NOT PURE DC power..
even in MOD, I have never felt any heat in the good quality motor wires...
the high amp draw time involved is in micro seconds... as its NOT PURE DC power..
even in MOD, I have never felt any heat in the good quality motor wires...
10-31-2018 | 08:15 PM
#5
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Joined: Jul 2018
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From: Florida
"If you do enough reading you will find that quality solid core wire has less resistance than stranded wire of the same AWG"
That really depends. At higher frequencies, the skin effect will mean stranded wire has less impedance. Even though these are DC motors, they switch on and off as the different phases are energised.
That really depends. At higher frequencies, the skin effect will mean stranded wire has less impedance. Even though these are DC motors, they switch on and off as the different phases are energised.
10-31-2018 | 08:28 PM
#6
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From: Florida
No doubt core failure is a liability that i minimized but still exists. In my case i had 10 awg stranded and 12 awg solid. The solid had less resistance. The stranded was high quality rc stuff with thick silicone jacket.
its not for everyone and I’ll keep an eye on resistance and a broken core. The nice thing about solid core is that you can bend it and it holds its shape so you can creep around fans and keep it off the motor. i control vibration with bends and support. One thing that is a little different than stranded is the solid core wants to hold its shape so if the bend or connector approach isnt right everything wants to push away from each other.
battery wires are stranded for sure but tucking a solid core under a top plate from the battery to the esc input power seems to work out.
its not for everyone and I’ll keep an eye on resistance and a broken core. The nice thing about solid core is that you can bend it and it holds its shape so you can creep around fans and keep it off the motor. i control vibration with bends and support. One thing that is a little different than stranded is the solid core wants to hold its shape so if the bend or connector approach isnt right everything wants to push away from each other.
battery wires are stranded for sure but tucking a solid core under a top plate from the battery to the esc input power seems to work out.
10-31-2018 | 08:34 PM
#7
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From: Florida
I agree. Im going of the idea that lower resistance equates to more speed like the motor resistance talk. i cant say i have a noticeable difference at my level but in a straight nobody has anything on me, corners are different.
10-31-2018 | 09:26 PM
#8
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So the skin depth at 4 kHz is about 1mm and that is already less than the wire radius for 10AWG and even 12 AWG. At 20 kHz, the skin depth is about .4mm. So skin effect is in play i.e. the current is not uniform across the wire. Bigger gauge wire always wins here because it has more surface area. One could argue that the stranded wire has more surface area, but as I mentioned above, the electrons have to transfer between strands which probably adds some resistance.
Bottom line is use whatever type of wire you like. I doubt that it makes any measurable difference in performance if all other things are equal. I do know from my own personal experience that 10 AWG wire can be pretty hard to solder because it conducts heat away from the joint so quickly. So I think the focus should be more on good soldering to motor/ESC tabs and connector pins.
10-31-2018 | 09:58 PM
#9
So I am an electrical engineer and spend a lot of time working with high speed pulses and many different types of cable. So this topic interested me. I did a little bit of digging and found conflicting claims about the resistivity of solid vs stranded wire. I looked at some wire tables that showed the resistivity for solid vs stranding (many different strand counts) all for the same AWG. According to the wire tables, for the most part the stranded versions are slightly more resistive than the solid. What I didn't find was much in the way of explanation for why that might be true. The first important fact is that for a given gauge, the cross-sectional area of copper is the same or very close to the same. However, with stranded wire, the strands are helical so in a 1 foot length of wire the strands are more than 1 foot. On the other had, all the strands touch each other. The current will always take the path of least resistance so the current has to "decide" whether it is easier flow down the longer strand or transfer from strand to strand. For that to happen, the surface condition (oxidation) and contact pressure between the strands is important. I think that in the end, the difference in resistance is pretty small, especially for the lengths of wire in our typical cars. There is probably more stray resistance is poor solder joints and in any connectors we use.
So the skin depth at 4 kHz is about 1mm and that is already less than the wire radius for 10AWG and even 12 AWG. At 20 kHz, the skin depth is about .4mm. So skin effect is in play i.e. the current is not uniform across the wire. Bigger gauge wire always wins here because it has more surface area. One could argue that the stranded wire has more surface area, but as I mentioned above, the electrons have to transfer between strands which probably adds some resistance.
Bottom line is use whatever type of wire you like. I doubt that it makes any measurable difference in performance if all other things are equal. I do know from my own personal experience that 10 AWG wire can be pretty hard to solder because it conducts heat away from the joint so quickly. So I think the focus should be more on good soldering to motor/ESC tabs and connector pins.
So the skin depth at 4 kHz is about 1mm and that is already less than the wire radius for 10AWG and even 12 AWG. At 20 kHz, the skin depth is about .4mm. So skin effect is in play i.e. the current is not uniform across the wire. Bigger gauge wire always wins here because it has more surface area. One could argue that the stranded wire has more surface area, but as I mentioned above, the electrons have to transfer between strands which probably adds some resistance.
Bottom line is use whatever type of wire you like. I doubt that it makes any measurable difference in performance if all other things are equal. I do know from my own personal experience that 10 AWG wire can be pretty hard to solder because it conducts heat away from the joint so quickly. So I think the focus should be more on good soldering to motor/ESC tabs and connector pins.
11-01-2018 | 01:09 AM
#11
Tech Master
Joined: Jul 2009
Posts: 1,416
From: Deep South Texas
aka, Silver solder. proper cleaning before and after...
standard solder, amateur solder-er... under powered soldering iron. = lots of resistance..
soldering for 55 years... professionally over 30 years... try soldering 40g wire to a 128 leg surface mount IC chip by hand.
Correct tool for the Right Job.
standard solder, amateur solder-er... under powered soldering iron. = lots of resistance..
soldering for 55 years... professionally over 30 years... try soldering 40g wire to a 128 leg surface mount IC chip by hand.
Correct tool for the Right Job.
11-01-2018 | 08:44 AM
#12
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According to one wire chart I found, 10 AWG solid is .1019" dia so the area is 8.155e-3 sq in.
One version of stranding is nineteen 23AWG strands. 23 AWG has a diameter of .0223". Each strand has an area of 4.0115e-4 sq in. Times 19 is 7.622e-3 sq in.
So they are not the same.
The table lists the resistance for solid as 1.0175 ohms/1000 feet
The Resistance for 19x 23AWG is 1.0916. ohms/1000feet
The ratio of the two resistance values is the same as the ratio of the two total areas. So the resistance difference for stranding is simply due to the actual copper cross-section. I looked through the table and in some cases the stranded version of some gauges is has less resistance than the solid. It just depends on the actual copper cross-section.
11-01-2018 | 01:05 PM
#13
Joined: Sep 2013
Posts: 2,351
From: Arizona
I love these kind of threads, I always learn a lot. But it does remind me of one of my favorite bosses. We would be getting into the minutia like this thread and he would look at us and state, "you are thinking too much!" 
11-01-2018 | 01:31 PM
#14
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I often get accused of over thinking things. 
and I can live with that
Thing is, like i said, I have spent a lot of time trying to understand the performance of wire and cable. Mostly coaxial cable for extremely fast pulses with risetimes measured in billionths of second. So when I see things like slid vs stranded, I HAVE to figure it out. Based on what I found in the wire tables there is no mystery. It is just due to differences in copper cross-sectional area. In a given gauge, solid and stranded don't have exactly the same copper area so they don't have the exact same resistance.
and I can live with thatThing is, like i said, I have spent a lot of time trying to understand the performance of wire and cable. Mostly coaxial cable for extremely fast pulses with risetimes measured in billionths of second. So when I see things like slid vs stranded, I HAVE to figure it out. Based on what I found in the wire tables there is no mystery. It is just due to differences in copper cross-sectional area. In a given gauge, solid and stranded don't have exactly the same copper area so they don't have the exact same resistance.
11-01-2018 | 05:46 PM
#15
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Tech Master
Joined: Jul 2018
Posts: 1,011
From: Florida
I often get accused of over thinking things. and I can live with that
Thing is, like i said, I have spent a lot of time trying to understand the performance of wire and cable. Mostly coaxial cable for extremely fast pulses with risetimes measured in billionths of second. So when I see things like slid vs stranded, I HAVE to figure it out. Based on what I found in the wire tables there is no mystery. It is just due to differences in copper cross-sectional area. In a given gauge, solid and stranded don't have exactly the same copper area so they don't have the exact same resistance.
and I can live with thatThing is, like i said, I have spent a lot of time trying to understand the performance of wire and cable. Mostly coaxial cable for extremely fast pulses with risetimes measured in billionths of second. So when I see things like slid vs stranded, I HAVE to figure it out. Based on what I found in the wire tables there is no mystery. It is just due to differences in copper cross-sectional area. In a given gauge, solid and stranded don't have exactly the same copper area so they don't have the exact same resistance.
Thank you
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