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21.1.1 The spacings through air and over surface in an appliance shall not be less than 1/16 inch (1.6
2 W+ l3 @5 X+ E! w: U: N# O2 Ymm) between uninsulated live parts of opposite polarity; and between a rigidly mounted uninsulated live
7 p0 e6 _: D* X" ^6 u1 } kpart and a dead metal part that either is exposed for persons to contact or may be grounded.
0 z$ {2 c, s) u3 ?& YException No. 1: If exact centering of the cold pin of a sheathed-type heating element is required to
3 A7 e& k9 ^* S" Q# lmaintain the 1/16 inch (1.6 mm) spacing, a spacing of 3/64 inch (1.2 mm) in one location is acceptable.7 Y3 E. O9 `$ V: o$ u4 Z
Exception No. 2: Spacings in an appliance that comply with 21.1.2 need not comply with 21.1.1.
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21.1.2 At closed-in points only, such as the screw-and-washer construction of an insulated terminal
+ i* o' l! [ n* L5 S! t L5 Gmounted in metal, a spacing of 3/64 inch (1.2 mm) is acceptable. Within a thermostat, except at contacts,3 \6 a, [( Y$ Y6 a! V+ U9 E
the spacings between uninsulated live parts on opposite sides of the contacts shall not be less than 1/32; O2 \3 [4 C0 q
inch (0.8 mm) through air and 3/64 inch (1.2 mm) over the surface of insulating material, and the& r/ w' U# N- F/ x6 p7 }& i" n
construction shall be such that the spacings are maintained permanently.3 L% c3 j( Q, q
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a. 21.1.1 中例外1,发热管里面有发热丝然后通过焊接一段延长出去(COLD PIN), 一般是圆柱体,EXACT centering 即COLD Pin 圆柱体中心,发热管有两端,意味着有两个cold pin, 这两个cold pin 圆柱体中心距离要求1.6mm, 后面说在一个位置可以有1.2mm 距离,什么叫一个位置(in one location)? 指的是那儿距离可以使1.2mm?: y0 b" E& }/ @, |
& s% {9 ~* N( ~5 G# `b. 21.1.2, except at contacts, contacts这里是指温控器里面的触点吗?还是指温控器端子引脚? 视乎是端子引脚对吧? 也就是说端子引脚要有1.6mm 电气间隙和爬电距离。然后说温控器两端子引脚间电气连接暴露导体可以是0.8mm 间隙,1.2mm 爬电?对吗? 什么样的结构是认为maintained permanently?. Q9 {5 I- ?: m
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