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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。
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8 J$ V5 k$ x1 b* f插头标示：E208969, type：TB303
9 f3 X, H7 ~$ C$ \' a) i7 r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
; a: q m6 y# h! r5 E2 W' rTIAN BAO ELECTRICAL LTD E208969 % u3 S) g$ Y% V7 d
ROOM B20, 12TH FL
H& S' e8 f( l3 Z5 M# oWONG KING INDUSTRIAL BLDG
& }) x- A* a& S8 L3 Q/ ]' e* X2 TAI YAU ST & s# l: D- V+ p' K) t: n V
SAN PO KONG, KOWLOON HONG KONG
7 \) p) C \0 h& y/ u
ZHONGSHAN GUZHEN HONGLI CABLE & ELECTRICAL FACTORY E215948
" ~4 k5 W! e( i, U1 L% ?! bHAI ZHOU DONG AN GONG RD ; r5 @7 B3 v3 B% G# }
GUZHEN 8 x. |, g+ ?8 d5 [) k; {) Q3 U( y
ZHONGSHAN, GUANGDONG 528422 CHINA
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& J$ j: Q- [+ `. FDecorative cords , Types SPT-1W, SPT-2W and XTW.
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- Q% ]% g0 G* o1 N- f, sHeater cord, Type HPN. & O* k. B$ I9 X& t
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Jacketed cords, Types SVT, SVTO, SVTOO, SJT, SJTO, SJTOO, ST, STO, STOO, SJTW, SJTOW, SJTOOW, STW and STOW.
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& p0 z% v- F, Q' B" y1 S. f8 ^Jacketed cords with -R suffix: Thermoplastic, Types SVT-R, SJTW-R.
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Parallel cords, Types NISPT-1, NISPT-2, SPT-1, SPT-2 and SPT-3. * A& Y* n" R6 R6 \/ f
7 o" G* ~7 ?3 I( v: r6 {( j
Parallel cords with -R suffix: Thermoplastic, Type SPT-2-R.
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补充一下： 5 ~/ F5 f3 e6 T1 N( o; d+ {
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。
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% b* c; t: X2 L$ W" K3 L- g) S事实上很少有18AWGSVT线长度仅1.5米会有0.178欧姆的
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7 w/ y4 [, H, x, r. |& z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？
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) K4 G7 X/ D! i) W& e标准也是有明确从插脚算起来的（UL1727）：
) Z, N$ D" g, O65.1 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. , c! X, i- D. o' F2 D- x$ K6 J
# z& ~" z) \, K0 c3 k) j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： ! w% K1 E! o' L* q/ E
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. $ q/ m. c4 Z) s9 P0 f# I% O$ S
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UL153： - d1 f' F- e& W7 J5 Y" x' V
136.2 Test method
7 _$ T& Z; T1 Q; n136.2.1 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). 8 |2 C, ^! R7 {& z+ s; w) v, m6 j
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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？
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发表于 2011-11-11 10:51
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发表于 2011-11-11 11:24