谁家的电源线？接地电阻0.176欧姆
cord set装在成品上接地测试Fail，25A/0.18Ohm，结果仅cord set阻值就达到0.176欧姆。插头标示：E208969, type：TB303
电线标示：(UL) E215948 SJTW 18AWGX3C VW-1 DRY 105oC AND WATER RESIST ANT 60oC C(UL) SJTW 18AWGX3C FT2 105oC-hONG L1
TIAN BAO ELECTRICAL LTD E208969
ROOM B20, 12TH FL
WONG KING INDUSTRIAL BLDG
2 TAI YAU ST
SAN PO KONG, KOWLOON HONG KONG
ZHONGSHAN GUZHEN HONGLI CABLE & ELECTRICAL FACTORY E215948
HAI ZHOU DONG AN GONG RD
GUZHEN
ZHONGSHAN, GUANGDONG 528422 CHINA
Decorative cords , Types SPT-1W, SPT-2W and XTW.
Heater cord, Type HPN.
Jacketed cords, Types SVT, SVTO, SVTOO, SJT, SJTO, SJTOO, ST, STO, STOO, SJTW, SJTOW, SJTOOW, STW and STOW.
Jacketed cords with -R suffix: Thermoplastic, Types SVT-R, SJTW-R.
Parallel cords, Types NISPT-1, NISPT-2, SPT-1, SPT-2 and SPT-3.
Parallel cords with -R suffix: Thermoplastic, Type SPT-2-R.
补充一下：
没错，接地电阻测试时大家都默认可以不包括电源线的，那是认为三根线（L、N、G）阻值一样大，在这种失效模式下阻值过大其实没有关系。测试仪器其实是带校正功能的，直接短路两根绿色的线归零就去掉了测试设备的阻值，大家无需担心测试方法的问题。接触电阻也不是问题，后来把线给剥掉后测试也是一样。
事实上很少有18AWGSVT线长度仅1.5米会有0.178欧姆的
但是这根电源线很蹊跷，用电桥法测试三根电线确实也都是毫欧级，但是地线带载25A测试达到0.178欧，而L和N线带载25A却达不到这个阻值，你认为这根线的问题在哪里？
标准也是有明确从插脚算起来的（UL1727）：
65.1 The resistance of the grounding path between any metal part that is required to be grounded (see 35.1.1) and the equipment grounding terminal or lead, or the point of attachment of the wiring system, or the grounding blade of an attachment plug, shall be no more than 0.1 ohm.
当然标准也在变，不一定从插头算起（UL1573）从地线接入点算的标准也是有明确说明的：
36.4 When an indicating device of the type described in 36.3 does not indicate continuity of the grounding circuit, an alternating current or a direct current of at least 25 amperes from a power supply of not more than 12 volts is to be passed from the point of connection of the equipment grounding means to a point in the grounding circuit and the points. The resistance in ohms is then calculated by dividing the drop in potential (in volts) by the current (in amperes). The resistance shall not exceed 0.1 ohm.
UL153：
136.2 Test method
136.2.1 The impedance between the point of connection of the equipment-grounding means and any other accessible metal part required to be grounded, shall be determined by applying a current of 25 amperes – derived from a 60 hertz source with a no-load voltage not exceeding 6 volts – between the grounding connection and the metal part in question. The resulting impedance is calculated by dividing the value of the measured voltage by the applied current (25 A).
大家考虑一下，为什么厂家要把地线做成与L和N电阻不一样？不同标准为什么有不同要求？
现在很多厂商会做假的,所以要特别小心! 感觉你的测量方法有问题，一般测量mΩ级的电阻应用电桥或4端法。按图示测量的电阻包含了两根测量引线的电阻、样品地线的电阻、引线和地线间的接触电阻。如此Σ电阻就大了。 接地电阻是不包含电源线的内阻的. 引用第2楼taihushui于2011-11-11 12:09发表的:
感觉你的测量方法有问题，一般测量mΩ级的电阻应用电桥或4端法。按图示测量的电阻包含了两根测量引线的电阻、样品地线的电阻、引线和地线间的接触电阻。如此Σ电阻就大了。
同意上楼的，你电线多长，怎么会这么长了，看看标准，电线本身就有电阻，插头或尾插也有电阻的，你要测量头还是尾，怎么会包括头和尾了，这样能测试准确不？
你的测试线夹不是原装的，方法上楼说了 测量方法出错，不能消除两个夹子的接触电阻（夹子好脏），（不能消除测量导线的电阻与夹子连接处的电阻），不能消除测量导线的电阻，不能消除测量导线与仪器连接处的接触电阻。这样也能测出电阻证明仪器没有设置成四端测试。要依据标称线径查出对应的电阻要求值，确定长度才能判定（去插头插尾）。铜对温度敏感，要折算成20度C的电阻。
其实不用测，基本上都不会达标。连珠海的最最最正规军的都生产流野，可见一斑。 上楼兄弟你测试过没有，测试机上有4个端都要接才行的。如图就是标准的测试线夹。 我们一般都是带电源线测接地电阻，很少发现不合格。
有不合格时才直接测端子。
难道我们用的电源线质量好？ 肯定要带一定长度电线才能测试，长度应该有要求的，且要减去电线本身的阻抗。
页:
[1]
2
