请教： UL444 火花测试

qing1234

5.1 Spark test after insulating


The voltage source of a dc or ac spark tester shall maintain the following test voltage under all nor

mal conditions of leakage current:

a) An essentially sinusoidal rms potential of 1750 V for an ac test;

b) 2500 V for a dc test. The current output of which the dc power supply is capable shall not exceed

5 mA. Any ripple shall not exceed 1 per cent. After a fault, the dc test voltage shall recover to the full

test voltage in 5 ms or less, unless 610 mm (2 ft) or less of the product travels through the electrode
e in the time that it takes for the full voltage recovery;

c) For conductor gauge sizes 22 – 30 AWG which are to be used in cables without coaxial membe

rs but with foam or foam skin insulation and protected by bonded metal shields, the following spar

k test voltage may be used:
Conductor size Test Voltage
22, 23 AWG 1500 V dc or 1050 V ac
24, 25 AWG 1200 V dc or 850 V ac
26–30AWG 1000Vdcor750Vac

d) For cables without bonded metal shields, and with foam insulation that is not more than 0.20 m

m (0.008 in) in average thickness and does not have a skin, the spark test voltage may be reduced

to 1250 V ac or 1750 V dc, provided that the dielectric strength test voltage required by Clause

5.3.5 is met.

这段内容看得有点糊涂，前辈们可否指导一下？
问题1. 首先我不理解d)中所涉及的skin在实物中是什么？
问题2. c）中foam 和foam skin 有何区别？
我想先把这个问题搞清楚了

民前八方

d中所指的skin是外皮层,针对发泡绝缘的结构,
根据不同发泡形式,可能会有：
a.发泡层, 所谓的foam,
b发泡层+外皮层(实心), 所谓的foam skin.
c内皮层(实心)+发泡层, 所谓的skin foam.
d.内皮层(实心)+发泡层+外皮层(实心), 所谓的skin foam skin.
所以foam与foam skin就差在有没有外皮层.
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帮兄弟修改下，便于理解。
呵呵。