USBCABLE電壓降計(jì)算公式

1、USB CABLE 電壓降計(jì)算公式,American Wire Gauge(AWG),Ohms/1 Meters Maximum,Voltage Drop Budget,Current ,V=IR Law,USB A-B CABLE Length Meters,額定電壓U就是用電器正常工作時(shí)的電壓公式其實(shí)跟平時(shí)學(xué)到的求電壓公式一樣，只要知道額定電流I（注意是額定）、額定功率P、用電器的電阻值R其中兩個(gè)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(dǎo)體電阻=導(dǎo)體長(zhǎng)度*(電阻系數(shù)/導(dǎo)體截面積),壓降=電流(負(fù)載)*導(dǎo)體電阻,這么來(lái)算吧：以送電線路主要考慮電壓降，設(shè)備接線主要考慮載流量的原則進(jìn)行計(jì)算。銅線電阻率是0.0172；線路電壓降以不超過(guò)供電電壓的5%為原則。就是400V供電線路的線路壓降是20V；380V的負(fù)載電壓

3、最低不得低于361V；45KW電機(jī)正常運(yùn)轉(zhuǎn)的電流在170A上下，而起動(dòng)電流要大很多，全壓起動(dòng)是電流是正常運(yùn)轉(zhuǎn)電流的5-7倍，降壓起動(dòng)要小得多。170安培電流要求線路電壓降在 380 x5% =19V以內(nèi)，如果搭線端電壓已經(jīng)降到400 x(15%)=380V，（已經(jīng)降了5%），還要考慮所接入的線路電流還會(huì)使搭線點(diǎn)的電壓進(jìn)一步下降，我們只能把接入的1000m線路電壓降設(shè)定為10V；那么線路阻抗應(yīng)小于：10（V） /170（A） = 0.0588（）線路電阻必須控制在0.0588以內(nèi)。根據(jù)導(dǎo)線電阻率，銅線截面為： 0.0172 ()x 1000(m) /0.0588()=292 m取大于等于300m

4、銅導(dǎo)線。 如果線路直接搭在配電變壓器400V端子上，情況會(huì)大為改觀：電壓降要求是：20V；20（V）/ 170（A）= 0.1176()0.0172 x 1000 / 0.1176 = 146 平方毫米，取150平方毫米。這樣在負(fù)載端還能有380V的標(biāo)準(zhǔn)電壓。,壓降=電流(0.5A)*導(dǎo)體長(zhǎng)度(L)*電阻系數(shù)(0.0175)/導(dǎo)體截面積(S),導(dǎo)體截面積(S)=D*D導(dǎo)體直徑平方*0.7854*N,多倏銅線集合徑(D)=開(kāi)根倏數(shù) N*1.154*D單支導(dǎo)體直徑,USB線材允許長(zhǎng)度計(jì)算：電壓0.125V/電流0.5A*電阻,注: 在溫度=20C時(shí)，銅的電阻系數(shù)為0.0175歐姆*平方毫米/米 ；

5、 在溫度=75C時(shí) 銅的電阻系數(shù)為0.0217歐姆*平方毫米/米 ,USB2.0 我司客戶要求 125mV最大 125mV就是USB2.0的最大壓降標(biāo)準(zhǔn)啊，125/500=0.25 OHM，也就是說(shuō)，不管你用的導(dǎo)體是多大的，也無(wú)論你的線材是多長(zhǎng)的，只要你的紅黑導(dǎo)體電阻不要超過(guò)0.25 OHM就OK了。例如，假設(shè)你的28#導(dǎo)體電阻量測(cè)出來(lái)是230 OHM/km，即0.23 OHM/M，那么壓降方面的長(zhǎng)度限制就是0.25/0.23=1.08米！,AWG線規(guī)表(參考文獻(xiàn):UL1581 5.3 20.1 20.4),AWG No,導(dǎo)體直徑(MM),截面積(MM),重量,DCR 25 C (/km),構(gòu)

6、成,導(dǎo)體絞距,備注,最大,最小,(cmil),標(biāo)準(zhǔn),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(dǎo)體絞距常規(guī)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