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安规的工作,我个人觉得,更重要的是利用自己对于安规的理解,实际贯彻到产品的设计过程中去。此贴是我之前做到一个分析报告。用于设计工程师的培训。但是,感觉还是有很多遗漏,例如关于快速熔断和慢熔断,延时熔断到选择依据等等。发上来供大家完善评阅。4 l2 R! m" K$ y( f5 P% {; V( ]
如下为引用标准GB4706.1—1998的内容,当熔断器的设置,是为了当模拟电子线路非正常测试时起保护作用的情况,熔断器应当按照如下进行考核,判断的条件为 “电路被充分保护”
6 [: O4 M. B. C, d: R$ e. B' OIf the safety of the appliance under any of the fault conditions depends on the operation of a
0 W3 k- U5 V3 y: t7 L# ]# [miniature fuse-link complying with IEC 60127, the test of 19.12 is carried out.
# c- i4 j' E+ d4 N0 Z' |% C19.12 If safety of the appliance depends upon the operation of a miniature fuse-link; |3 f0 v' w) ^* K
complying with IEC 60127 during any of the fault conditions specified in 19.11.2, the test is
, S' J# H' t! X1 Lrepeated but with the miniature fuse-link replaced by an ammeter. If the current measured5 {- k# g# Q7 M1 ~$ x ^0 p& X
– does not exceed 2,1 times the rated current of the fuse-link, the circuit is not considered to7 Q+ \* J, H0 y, m
be adequately protected and the test is carried out with the fuse-link short-circuited;
: m7 {6 X* R# J6 t5 V$ q– is at least 2,75 times the rated current of the fuse-link, the circuit is considered to be! {% K6 X- j7 A* j" T
adequately protected;
6 O- V3 F3 a' T( N) {– is between 2,1 times and 2,75 times the rated current of the fuse-link, the fuse link is
9 M8 e; U) L# rshort-circuited and the test is carried out# ^1 D; u3 ^ N/ {5 b
• for the relevant period or for 30 min, whichever is the shorter, for quick acting fuselinks;5 ~4 N3 i {/ ~- J
• for the relevant period or for 2 min, whichever is the shorter, for time lag fuse-links.
% B, {$ G7 e* y. g% p s) k; ]NOTE 1 In case of doubt, the maximum resistance of the fuse-link has to be taken into account when determining
# X$ T" o6 K8 o. j; B- C2 D- Qthe current.
" f* K- S! Q" Y6 G/ W( w1 e( `9 j: ONOTE 2 The verification whether the fuse-link acts as a protective device is based on the fusing characteristics
3 z' O+ G0 E8 l0 H5 A4 jspecified in IEC 60127, which also gives the information necessary to calculate the maximum resistance of the4 g+ T" C }; t; E6 R5 t
fuse-link.5 m7 D" w" x/ g4 ~( V! c- v/ x: U
NOTE 3 Other fuses are considered to be intentionally weak parts in accordance with 19.1.7 G( t1 L. F" [; [9 }
分析方法如下:
$ I& ?6 A( I8 p* J3 H1、 明确熔断器的设置,是用于在何种电子线路故障时起保护作用;" z( ~. ~9 E2 r" _" g5 b- D
2、 计算或者测试,在单一故障发生的情况下,通过熔断器的电流;
/ Z% V; y$ D# L2 R8 {7 f( h% o3、 测试和选择方法:6 m9 h$ s& y3 q# G2 j
1)、用电流表代替熔断器的两端,逐个模拟单一故障,记录电流表的测试值;, C8 C' U1 ^+ a/ @/ w0 G! l
2)、电流表代替时,应充分考虑电流表与熔断器电阻的差异,尽量做到两者内阻相等;
2 o* t! y0 K8 |* Z7 }4 I) I, e% `3)、用电流表测得的电流值(选取模拟故障时,需要熔断器动作来保护的最小电流值),除以2.75,所得出的值为熔断器的最大额定电流;
4 M. [1 ?& X. F c+ L4)、熔断器的额定电流,必须大于电子线路正常工作时通过熔断器位置的电流。(考虑正常电压波动,测量正常工作电流时,输入电压为AC240V,50Hz)。
) U( w8 \3 q% @& K% V4、当按照测试值采用了熔断器之后,须进行验证。若模拟电子线路故障是,熔断器立即动作,则在同样条件下重复测试一次,作为薄弱位置的可靠保护确认。
( o) L4 k* }. B% |: `' e; A$ d$ e- M抛砖引玉,请高手完善。 |
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