USBCABLE电压降计算公式

1、USB CABLE 電壓降計算公式,American Wire Gauge(AWG),Ohms/1 Meters Maximum,Voltage Drop Budget,Current ,V=IR Law,USB A-B CABLE Length Meters,额定电压U就是用电器正常工作时的电压公式其实跟平时学到的求电压公式一样，只要知道额定电流I（注意是额定）、额定功率P、用电器的电阻值R其中两个就行了，公式有U=IR=P/I=P/(R2)。,28,0.232,0.125V ,0.5A,0.125V=0.5A*0.232,1.078M,26,0.146,0.125V ,0.5A,0.125

2、V=0.5A*0.146,1.72M,24,0.0909,0.125V ,0.5A,0.125V=0.5A*0.0909,2.75M,22,0.0574,0.125V ,0.5A,0.125V=0.5A*0.0574,4.35M,20,0.0358,0.125V ,0.5A,0.125V=0.5A*0.0358,7.0M,導體電阻=導體長度*(電阻系數/導體截面積),壓降=電流(負載)*導體電阻,这么来算吧：以送电线路主要考虑电压降，设备接线主要考虑载流量的原则进行计算。铜线电阻率是0.0172；线路电压降以不超过供电电压的5%为原则。就是400V供电线路的线路压降是20V；380V的负载电压

3、最低不得低于361V；45KW电机正常运转的电流在170A上下，而起动电流要大很多，全压起动是电流是正常运转电流的5-7倍，降压起动要小得多。170安培电流要求线路电压降在 380 x5% =19V以内，如果搭线端电压已经降到400 x(15%)=380V，（已经降了5%），还要考虑所接入的线路电流还会使搭线点的电压进一步下降，我们只能把接入的1000m线路电压降设定为10V；那么线路阻抗应小于：10（V） /170（A） = 0.0588（）线路电阻必须控制在0.0588以内。根据导线电阻率，铜线截面为： 0.0172 ()x 1000(m) /0.0588()=292 m取大于等于300m

4、铜导线。 如果线路直接搭在配电变压器400V端子上，情况会大为改观：电压降要求是：20V；20（V）/ 170（A）= 0.1176()0.0172 x 1000 / 0.1176 = 146 平方毫米，取150平方毫米。这样在负载端还能有380V的标准电压。,壓降=電流(0.5A)*導體長度(L)*電阻系數(0.0175)/導體截面積(S),導體截面積(S)=D*D導體直徑平方*0.7854*N,多倏銅線集合徑(D)=開根倏數 N*1.154*D單支導體直徑,USB線材允許長度計算：電壓0.125V/電流0.5A*電阻,注: 在温度=20C时，铜的电阻系数为0.0175欧姆*平方毫米/米 ；

5、 在温度=75C时 铜的电阻系数为0.0217欧姆*平方毫米/米 ,USB2.0 我司客户要求 125mV最大 125mV就是USB2.0的最大压降标准啊，125/500=0.25 OHM，也就是说，不管你用的导体是多大的，也无论你的线材是多长的，只要你的红黑导体电阻不要超过0.25 OHM就OK了。例如，假设你的28#导体电阻量测出来是230 OHM/km，即0.23 OHM/M，那么压降方面的长度限制就是0.25/0.23=1.08米！,AWG線規表(參考文獻:UL1581 5.3 20.1 20.4),AWG No,導體直徑(MM),截面積(MM),重量,DCR 25 C (/km),構

6、成,導體絞距,備注,最大,最小,(cmil),標準,最小,kg/km,kg/m,銅,鍍錫銅,鋁,inches,mm,10,2.614,2.537,10380,5.264,5.103,47.2,0.0472,3.408,3.545,5.59,2.5,64,12,2.07,2.01,6530,3.311,3.21,29.34,0.0293,5.42,5.64,8.89,2,51,14,1.64,1.6,4107,2.083,2.02,18.55,0.0186,8.61,8.96,13.9,2,51,16,1.3,1.26,2583,1.31,1.27,11.62,0.0116,13.48,13.8

7、8,22.11,7/0.511 19/0.287 26/0.254 65/0.16 105/0.12,2,51,18,1.03,1,1620,0.822,0.798,7.264,0.0073,21.43,22.06,35.15,1/1.02 7/0.404 19/0.254 34/0.180 41/0.160 65/0.127,2,51,20,0.82,0.798,1020,0.517,0.503,4.615,0.0046,34.08,35.45,55.9,1/0.8 7/0.320 10/0.254 19/0.203 21/0.180 26/0.160 42/0.127,1.25,32,22

8、,0.65,0.63,640.4,0.325,0.314,2.887,0.0029,54.2,56.4,88.9,1/0.65 7/0.254 17/0.16 26/0.127,0.8,20,24,0.516,0.5,404,0.205,0.199,1.823,0.0018,86.1,89.6,139,1/0.5 7/0.203 11/0.160 19/0.127 42/0.079,0.7,18,26,0.409,0.396,253,0.128,0.126,1.14,0.0011,134.8,138.8,221.1,1/0.4 7/0.160 10/0.127 19/0.102,0.6,15,

9、28,0.323,0.312,159.8,0.081,0.079,0.715,0.0007,214.3,220.6,351.5,1/0.32 7/0.127 19/0.079,0.5,12.7,導體絞距常規是:6.08.4MM之間30,0.257,0.249,100.5,0.051,0.05,0.45,0.0005,340.8,354.5,559,1/0.26 7/0.102,0.4,10,32,0.203,63.21,0.032,0.288,0.0003,542,564,889,7/0.08 1/0.203,0.35,8.9,34,0.16,39.75,0.02,0.179,0.0002,861,896,1390,1/0.16,36,0.127,25,0.01