论坛推荐第二波－防触电讨论

fasten

最佳讨论将获取五个安规威望, 所有技术讨论(包括提问)者将获取一个安规威望, 水贴删除!
- Z1 r; O' Y5 C讨论结束后才会一次性补给所有参与者威望!
最佳讨论将送给参与较多, 讨论积极, 讨论深刻的会员! 有异议者, 可以提出另奖五个威望, 但最多再送出两个!

请不要讨论是否该如何分贴讨论! 违者扣分处理!
) N* Q' P  z; P' A1 D

0 D2 R9 l/ _1 ?讨论议题:
  X, P3 ~5 D6 U& N% W% T& P防止接触带电部件

/ X5 a4 K; c" s4 a讨论背景:
. P4 T5 u/ t4 y6 l* O2 H) r. G在所有的电类产品标准裡,防触电防火防机械电气等伤害是标准的主线,但防触电是最难以处理和易混淆的一个项目. 也是标准理解的一个难点,因为产品的使用条件不一致,防触电要求也可能不一致,EN60335就列出了一大堆的测试指.

标准范例:
EN60335-1  Clause 8 Protection against access to live parts
3 X$ w0 w* N# FUL153-2002 Clause 23 Accessibility of Live Parts
" C& F1 D9 e! v1 w. w) q6 D& P
, y: a- D; ]: h. d6 u9 x5 ]推荐议题:
请不要试图用回答方式来讨论以下所列议题,一般要求一贴只能谈一个议题!
8 l( k" u# `- H4 R01. 测试标准间的区别（如EN60335,EN60312,EN60598,EN60950及一些UL标准)
0 n/ g$ Y, ]0 S. P9 x) D. k8 H02. 测试指的选择/制作/使用
+ z9 I* f3 g; b! ?/ P03. 测试部位的选取
4 ?* H0 W% e: ^6 c04. 豁免要求范例
05. 测试经验分享
# m6 o- f6 U# H7 j06. 一些特殊产品的特殊要求
/ c. g1 Z' a4 n$ h. e
- C7 T$ b# C+ n8 G2 V  f& Y
欢迎增加不同议题!
) U7 y/ @: ]: `+ A3 w& K! S( h
  K- {3 v' t, [: J& r+ k: M  z; Z本议题由有奖征集安规技术话题的nellhu提供!

fasten

8 Protection against access to live parts
; k6 J6 b' L4 k" s. I8.1 Appliances shall be constructed and enclosed so that there is adequate protection against accidental contact with live parts.
Compliance is checked by inspection and by the tests of 8.1.1 to 8.1.3, as applicable, taking into account 8.1.4 and 8.1.5.
8.1.1 The requirement of 8.1 applies for all positions of the appliance when it is operated as in normal use, and after the removal of detachable parts.
NOTE This excludes the use of screw-type fuses and screw-type miniature circuit breakers which are accessible without the aid of a tool.
Lamps located behind a detachable cover are not removed, provided that the appliance can be isolated from the supply mains by means of a plug or an all-pole switch. However, during insertion or removal of lamps which are located behind a detachable cover, protection against contact with live parts of the lamp cap shall be ensured.
# j8 Y6 f' k# Z# H9 RTest probe B of IEC 61032 is applied without appreciable force, the appliance being in every possible position except that appliances normally used on the floor and having a mass exceeding 40 kg are not tilted. Through openings, the test probe is applied to any depth that the probe will permit and is rotated or angled before, during and after insertion to any position. If the opening does not allow the entry of the probe, the force on the probe in the straight position is increased to 20 N. If the probe then enters the opening, the test is repeated with the probe in the angled position.
& d' U$ y6 T* [. uIt shall not be possible to touch live parts or live parts protected only by lacquer, enamel, ordinary paper, cotton, oxide film, beads, or sealing compound except self-hardening resins, with the probe.
8.1.2 Test probe 13 of IEC 61032 is applied without appreciable force through openings in class 0 appliances, class II appliances and class II constructions, except for those giving access to lamp caps and live parts in socket-outlets.
NOTE Appliance outlets are not considered to be socket-outlets.
# _4 a" Z$ V" v; ?9 D4 M% F: f: oThe test probe is also applied through openings in earthed metal enclosures having a nonconductive coating such as enamel or lacquer.
7 I" Q3 d7 [. Y3 IIt shall not be possible to touch live parts with the test probe.
8 K, i5 z; L+ E5 \8.1.3 Instead of test probe B and test probe 13, for appliances other than those of class II, test probe 41 of IEC 61032 is applied without appreciable force to live parts of visibly glowing heating elements, all poles of which can be disconnected by a single switching action. It is also applied to parts supporting such elements, provided that it is obvious from the outside of the appliance, without removing covers and similar parts, that these supporting parts are in contact with the element.
It shall not be possible to touch these live parts.
* s! P9 n& V9 {, u" lNOTE For appliances provided with a supply cord and without a switching device in their supply circuit, the withdrawal of the plug from a socket-outlet is considered to be a single switching action.
8.1.4 An accessible part is not considered to be live if – the part is supplied at safety extra-low voltage, provided that
• for a.c., the peak value of the voltage does not exceed 42,4 V,
• for d.c., the voltage does not exceed 42,4 V,
or
/ P, L1 B8 b# X* k* I– the part is separated from live parts by protective impedance.
If protective impedance is used, the current between the part and the supply source shall not exceed 2 mA for d.c., its peak value shall not exceed 0,7 mA for a.c. and
– for voltages having a peak value over 42,4 V up to and including 450 V, the capacitance shall not exceed 0,1F,
– for voltages having a peak value over 450 V up to and including 15 kV, the discharge shall not exceed 45 C.
+ k" |* H9 S; \) }" cCompliance is checked by measurement, the appliance being supplied at rated voltage.
$ T5 Z- j  L3 x3 `+ EVoltages and currents are measured between the relevant parts and each pole of the supply source. Discharges are measured immediately after the interruption of the supply.
: e# b* d+ I! t: `NOTE Details of a suitable circuit for measuring the current are given in figure 4 of IEC 60990.
. z$ k0 \2 X+ Q8 v8 _: O8.1.5 Live parts of built-in appliances, fixed appliances and appliances delivered in separate units, shall be protected at least by basic insulation before installation or assembly.
Compliance is checked by inspection and by the test of 8.1.1.
8.2 Class II appliances and class II constructions shall be constructed and enclosed so that there is adequate protection against accidental contact with basic insulation and metal parts separated from live parts by basic insulation only.
) C, a1 x7 i5 j) w# }It shall only be possible to touch parts which are separated from live parts by double insulation or reinforced insulation.
3 \& o1 `# X) p. OCompliance is checked by inspection and by applying test probe B of IEC 61032, as described in 8.1.1.
NOTE 1 This requirement applies for all positions of the appliance when it is operated as in normal use and after removing detachable parts.
NOTE 2 Built-in appliances and fixed appliances are tested after installation.

fasten

23 Accessibility of Live Parts
0 x$ Y. X3 A8 ?6 i- h7 ?23.1 Each part or device that is required by Enclosures, Section 9, to be enclosed shall be located or shielded so that it is not accessible to unintentional contact by persons during normal use, including relamping, replacement of an automatic starter, or other user maintenance services.
Exception No. 1: An uninsulated live part that operates at a potential of 30 volts rms or less and 42.4 volts peak and is able to be accessible in accordance with Secondary Low Voltage Circuits, Section 38.
. i" q) c1 N$ w, Z' ]" o% {Exception No. 2: Wiring that is visible and follows the contour of the portable luminaire is able to be
accessible during relamping, when it is not spliced and strain relief is maintained at all wiring terminations.
# x" p1 W+ P% N5 e3 R" l23.2 A live part is determined to be inaccessible when a probe as illustrated in Figure 23.1 is unable to be manipulated such that it touches any part. The probe is to be articulated into any configuration and rotated or angled to any capable position before, during, or after inserting into the opening.
23.3 All parts that are removable without the use of tools shall be removed when determining accessibility in accordance with 23.2.
5 K8 {: R- G) K& L1 hException No. 1: A phenolic or metal lampholder shell that is secured by a twist or snap-fit does not
" R* n, v% T) B( Brequire removal.
& A! ~* c: z$ I! qException No. 2: An automatic starter does not require removal.

cuijiude

外行人問個問題﹐觸電的概念是否跟平時講的電擊是一樣的﹐從保護設備本身及與之相接觸的生物為准則啊﹖

fasten

引用第3楼cuijiude于2007-12-24 14:12发表的  :
. n& l& n) q6 j* P* {7 L1 m外行人問個問題﹐觸電的概念是否跟平時講的電擊是一樣的﹐從保護設備本身及與之相接觸的生物為准則啊﹖

本議題指的是人體可能接觸到帶電體（live parts）可能性．也就是以live parts為臨界點．
: [6 `/ X0 l7 k標準認為，live parts包含基本絕緣所包覆的帶電體，同時象漆包線也被所有標準定義為live parts．

觸電機理還是比較的複雜，但是在安全標準裡，觸電與你所述是有區別的．比如，人體如果踫到基本絕緣，一般來講是不會有電擊的感覺，但是在標準裡，他認為是踫到了帶電體，防觸電已經失敗．
% S7 g/ Y0 W$ |3 b
- E0 _% _9 D# s0 |9 J1 j# n7 b同時，安全標準同樣考慮將接觸電流量化作為觸電的一種表現．這個值就與平時大家感應到的電擊有點類似了．這是大家平時認為的觸電基本是一個概念．

: O' Z# \/ M2 C# s) p+ C4 o, `標準視絕緣擊穿為一種防觸電失敗的一種可能性，絕緣失敗並不代表人立即會觸電，但會有安全隱患，故視為防觸電失敗！

longer

触电和电击是一个道理，2种说法，按标准上的理解就是触及带42.4V Peak ac,或60Vdc以上的带电端子是危险的。人体触电时，致命的因素是通过人体的电流，而不是电压，但是当电阻不变时，电压越高，通过导体的电流就越大。因此，人体触及到带电体的电压越高，危险性越大。但不论是高压还是低压，触电都是危险。电流通过人体的持续时间是影响电击伤害程度的又一重要因素。人体通过电流的时间越长，人体电阻就越降低，流守的电流就越大，后果就越严重。另一方面，人的心脏每收缩、扩张一次，中间约有0.1秒间歇，这0.1秒对电流最敏感。如果电流在这一瞬间通过心脏，即使电流很小，（零点几毫安）也会引起心脏震颤；如果电流不在这一瞬间通过，即使电流较大，也不至于引起心脏麻痹。由此可知，如果电流持续时间超过0.1秒，则必然与心脏最敏感的间隙相重合而造成很大的危险。
5 b! ~7 y$ F' d& m/ Z有资料表明60HZ的电源频率比50HZ还要危险。象美国，日本这些国家都用60HZ的电源，而且电压为110V,那么功率一定的情况下，电流就很大，所以个人认为230/50HZ的电源比110V/60HZ的电源要安全一点

roy517

个人认为防触电应该注意以下几点：
4 r7 P1 I/ [! }) F9 u! [1.结构的设计满足绝缘距离的要求；
2.材料满足电气强度和漏电流的要求；
- H# ]4 y7 t1 X7 D$ o3.人手可触摸的电路满足SELV电路的要求。

赵杰

个人看法哈
人与带电体之间必须满足两套或两套以上的防护措施
象我们接触最多的Ⅰ类器具也就是3个插头的家用电器
. d' k' o* R% r他就要求我们与器具的带电体满足二重绝缘或加强绝缘（或Ⅱ类结构），
9 U' r. H4 x4 ?4 O当然如果接触的是金属部件：
& |: Q, B2 r$ |+ ?5 G9 \如果金属部件没有接地，同样要求满足加强绝缘或二重绝缘。
如果有接地措施，就要求与此金属部件接触的部件满足基本绝缘。
* {! [3 j: X9 ~8 C0 n$ r" w即人体不能直接碰触到Ⅰ类器具的基本绝缘，否则是不满足穿透绝缘要求的。
( j5 M$ c& H0 |- W7 ?Ⅱ类器具就直接要求我们与带电部件之间必须满足二重绝缘或加强绝缘
" [4 _4 H- B7 ^& r" u& y$ cⅢ类就要求安全特低电压供电了。
所以我感觉判定器具是否满足防触电的要求必须对器具的分类做明确判定。然后再利用标准中的试验指判定具体的器具、结构是否满足要求
- R! }6 H4 S  o) h6 T9 }
个人看法哈，请高手赐教~~

dingcwu

补充一点，对于可触及的安全电压还要考虑它的变压器是否满足安全隔离变压器的要求，不然就算是低于42V的电压也是不能触及的。

applevening

IEC系列 的标准多吗