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各位大俠:

有一問題請教:

關(guān)於UL STYLE 21491中的USE有說明以下內(nèi)容,我想了解一下其中的Class 2是代表什麼意思?

謝謝啦!

USE   Internal or external wiring in class 2 circuits only

class 0/1/2/3 分別指的是設(shè)備類型，在這就表示這些設(shè)備中的用線。其分類如下：
  1 ) 0類設(shè)備是指靠基本絕緣作為觸電防護設(shè)備。這些設(shè)備一旦基本絕緣失效，設(shè)備的安全性取決于用電環(huán)境。由于0類設(shè)備的觸電防護條件較差，在一些工業(yè)發(fā)達國家已逐漸禁止生產(chǎn)這類設(shè)備。
  2) 1類設(shè)備是指觸電防護不僅靠基本絕緣，還需將外漏可導(dǎo)部分與設(shè)施固定布線的保護線相聯(lián)接的設(shè)備，也就是說需要采用保護接地或保護接零的設(shè)備。
  3) 2類設(shè)備是指具有加強絕緣或雙重絕緣的設(shè)備，這類設(shè)備的外殼一般不得與保護線相連。
  4) 3類設(shè)備是指靠安全特低電壓供電的設(shè)備。
Please see explanation in English below：

［moveitgogo 在 2010-6-2 21:52:32 編輯過］

［moveitgogo 在 2010-6-2 21:53:04 編輯過］

1）class 0: These appliances have no protective-earth connection and feature only a single level of insulation and were intended for use in dry areas. In most countries, the sale of Class 0 mains-voltage appliances is prohibited today, as a single fault could cause an electric shock or other dangerous occurrence. The International Electrotechnical Commission is in the process of removing provisions for Class 0 devices from its standards. It can be expected that the Class 0 concept will eventually disappear from the international market, in favour of Class II devices。

2) class 1:These appliances must have their chassis connected to electrical earth (US: ground) by an earth conductor (coloured yellow/green in most countries, green in the U.S., Canada and Japan). A fault in the appliance which causes a live conductor to contact the casing will cause a current to flow in the earth conductor. This current should trip either an overcurrent device (fuse or circuit breaker) or a residual current circuit breaker (ground fault circuit interrupter [GFCI]) which will cut off the supply of electricity to the appliance.

3) class 2:A Class II or double insulated electrical appliance is one which has been designed in such a way that it does not require a safety connection to electrical earth (US: ground).The basic requirement is that no single failure can result in dangerous voltage becoming exposed so that it might cause an electric shock and that this is achieved without relying on an earthed metal casing. This is usually achieved at least in part by having two layers of insulating material surrounding live parts or by using reinforced insulation.In Europe, a double insulated appliance must be labelled "Class II", "double insulated" or bear the double insulation symbol (a square inside another square).

4)class 3:A Class III appliance is designed to be supplied from a SELV (Separated or Safety Extra-Low Voltage) power source. The voltage from a SELV supply is low enough that under normal conditions a person can safely come into contact with it without risk of electrical shock. The extra safety features built into Class I and Class II appliances are therefore not required. For medical devices compliance with Class III is not considered sufficient protection .

謝了,樓上的大俠 !

我還有點質(zhì)疑:

針對UL在STYLE PAGE上要求這些不同的設(shè)備類型,在電線設(shè)計上要做哪些區(qū)分呢?

在結(jié)構(gòu)上是否要注意些什麼?

此Class 2非彼Class II，一般來講，UL的Class 2的概念是指通過變壓器隔離的低壓回路。

電線就參考UL758, UL1581而已