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Esprit Model . Thunder Power RC . Real Raptors

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e-Electric Conversions > E Raptor AP machine
 
 
QueeQueg
Senior Heliman
Location: West Texas

I assume when you say smaller wires you mean AWG.

Why would a smaller wire yet more strands have a higher resistence than a larger wire less strands if the are the same gauge.

The electrons travel on the surface of the wire and henceforth the more surface area (more strands) the less resistance at a given wire gauge.

The same is true with the 10 to 13G silcone wires that we use to transer sometimes in excess of 100A from the battery to the ESC and from the ESC to the motor. They are only able to do this due to the very small individual wires and lots of surface.

If you tried to do 100As down a 10G single strand it would melt almost instantly like a buss fuse.
12-23-2007 07:06 PM
 
 
eyeinsky
Senior Heliman
Location: Fall River, Nova Scotia, Canada

Motor windings wires are single strand. So lower kv motor will have smaller wire diameter wire and larger AWG number.

What meant was #12AWG wire has less resistance than #20AWG wire. The number #20AWG is the smaller of the two wires. Not say that 12 or 20AWG is the winding size I don't know the actual size.

Single strand 10AWG wire would carry the same load as the malty stand wire. It is actual lager diameter for the same rating but has the advantage of being more flexible. AWG is rating more than size. Aluminum wire has the same rating but because aluminum has higher resistance the wire is actually larger for the same rating.

Hard job competing with gravity.
12-24-2007 05:17 AM
 
 
QueeQueg
Senior Heliman
Location: West Texas

Please explain to me how were getting 100As through the fine stranded 13G that most controllers have on the battery side with some using 10G while 10G single strand is rated for 25A.

And I guarantee you that 100A will melt single strand 10G in short order.

It will get hot, resistance will rise and the wire will melt very quickly.

Also I have yet to see a Brushless Motor with single strands.

As an example the Kohler Actro standards use less strands of larger gauge wire. The Max versions use more strands of smaller gauge wire for the exact same wind but a lower resistance rating.
12-24-2007 11:48 PM
 
 
eyeinsky
Senior Heliman
Location: Fall River, Nova Scotia, Canada

It is the same reason AC power requires less wire size. Your ESC produce pulse of DC through one of three field wires alternating, witch are comprised of a winding single strand. DC power into the ESC is continuous but power out is pulsating around the field coil driving the permanent magnets. Continuous power would burn the wire up and because it divided between three wires and only a pulse it allows for a smaller wire gauge.

That is the theory that I think be true but not 100% sure. I can look into this a little more it but it will take some time.

Maybe some one else has better under standing of this process?

Here some data that just googled. Note stranded wires are equivalent cross section not the same size but equal in AWG rating wich is based on solid wires. Skin effect may play some part in the equation but I am not sure.


The table below shows various data including both the resistance of the various wire gauges and the allowable current (ampacity) based on plastic insulation. The diameter information in the table applies to solid wires. Stranded wires are calculated by calculating the equivalent cross sectional copper area. The table below assumes DC, or AC frequencies equal to or less than 60 Hz, and does not take skin effect into account. Turns of wire is on a best-case scenario when winding tightly packed coils.

The skin effect is the tendency of an alternating electric current (AC) to distribute itself within a conductor so that the current density near the surface of the conductor is greater than that at its core. That is, the electric current tends to flow at the "skin" of the conductor. The skin effect causes the effective resistance of the conductor to increase with the frequency of the current. Skin effect is due to eddy currents set up by the AC current


AWG Diameter Turns of wire Area Copper
resistance Copper
resistance[3] Copper wire
current rating
with 60 °C raceway Approximate
stranded metric
equivalents
(inch) (mm) (per inch) (per cm) (kcmil) (mm²) (Ω/1 km) (Ω/1000 ft) (A)
0000 (4/0) 0.460 11.7 2.17 0.856 212 107 0.16* 0.049* 195
000 (3/0) 0.410 10.4 2.44 0.961 168 85.0 0.2* 0.062* 165
00 (2/0) 0.365 9.27 2.74 1.08 133 67.4 0.25* 0.077* 145
0 (1/0) 0.325 8.25 3.08 1.21 106 53.5 ~0.3281 ~0.1 125
1 0.289 7.35 3.46 1.36 83.7 42.4 0.4* 0.12* 110
2 0.258 6.54 3.88 1.53 66.4 33.6 0.5* 0.15* 95
3 0.229 5.83 4.36 1.72 52.6 26.7 85 196/0.4
4 0.204 5.19 4.89 1.93 41.7 21.2 0.8* 0.24* 70
5 0.182 4.62 5.50 2.16 33.1 16.8 126/0.4
6 0.162 4.12 6.17 2.43 26.3 13.3 1.5* 0.47* 55
7 0.144 3.66 6.93 2.73 20.8 10.5 80/0.4
8 0.128 3.26 7.78 3.06 16.5 8.37 2.2* 0.67* 40
9 0.114 2.91 8.74 3.44 13.1 6.63 >84/0.3
10 0.102 2.59 9.81 3.86 10.4 5.26 3.2772 0.9989 30
11 0.0907 2.30 11.0 4.34 8.23 4.17 4.1339 1.26
12 0.0808 2.05 12.4 4.87 6.53 3.31 5.21 1.588 20
13 0.0720 1.83 13.9 5.47 5.18 2.62 6.572 2.003
14 0.0641 1.63 15.6 6.14 4.11 2.08 8.284 2.525 15
15 0.0571 1.45 17.5 6.90 3.26 1.65 10.45 3.184
16 0.0508 1.29 19.7 7.75 2.58 1.31 13.18 4.016 10
17 0.0453 1.15 22.1 8.70 2.05 1.04 16.614 5.064
18 0.0403 1.02 24.8 9.77 1.62 0.823 20.948 6.385
19 0.0359 0.912 27.9 11.0 1.29 0.653 26.414 8.051
20 0.0320 0.812 31.3 12.3 1.02 0.518 33.301 10.15
21 0.0285 0.723 35.1 13.8 0.810 0.410 41.995 12.8
22 0.0253 0.644 39.5 15.5 0.642 0.326 52.953 16.14
23 0.0226 0.573 44.3 17.4 0.509 0.258 66.798 20.36
24 0.0201 0.511 49.7 19.6 0.404 0.205 84.219 25.67
25 0.0179 0.455 55.9 22.0 0.320 0.162 106.201 32.37
26 0.0159 0.405 62.7 24.7 0.254 0.129 133.891 40.81
27 0.0142 0.361 70.4 27.7 0.202 0.102 168.865 51.47
28 0.0126 0.321 79.1 31.1 0.160 0.0810 212.927 64.9
29 0.0113 0.286 88.8 35.0 0.127 0.0642 268.471 81.83
30 0.0100 0.255 99.7 39.3 0.101 0.0509 338.583 103.2
31 0.00893 0.227 112 44.1 0.0797 0.0404 426.837 130.1
32 0.00795 0.202 126 49.5 0.0632 0.0320 538.386 164.1
33 0.00708 0.180 141 55.6 0.0501 0.0254 678.806 206.9
34 0.00630 0.160 159 62.4 0.0398 0.0201 833 260.9
35 0.00561 0.143 178 70.1 0.0315 0.0160 1085.958 331
36 0.00500 0.127 200. 78.7 0.0250 0.0127 1360.892 414.8
37 0.00445 0.113 225 88.4 0.0198 0.0100 1680.118 512.1
38 0.00397 0.101 252 99.3 0.0157 0.00797 2127.953 648.6
39 0.00353 0.0897 283 111 0.0125 0.00632 2781.496 847.8
40 0.00314 0.0799 318 125 0.00989 0.00501 3543.307 1080

Hard job competing with gravity.
12-25-2007 07:13 AM
 
 
2 pages [ <<    <     1     ( 2 )    >    >> ]1775 viewsPOST REPLY
Mikado Modellhubschrauber . GrandRC . CanoMod

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e-Electric Conversions > E Raptor AP machine
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