标题: 关于家用电器内，电子线路设计，熔断丝的参数选择问题 [打印本页] 作者: 日夏清 时间: 2011-12-27 11:47 标题: 关于家用电器内，电子线路设计，熔断丝的参数选择问题 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。
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”
If the safety of the appliance under any of the fault conditions depends on the operation of a
miniature fuse-link complying with IEC 60127, the test of 19.12 is carried out.
19.12 If safety of the appliance depends upon the operation of a miniature fuse-link
complying with IEC 60127 during any of the fault conditions specified in 19.11.2, the test is
repeated but with the miniature fuse-link replaced by an ammeter. If the current measured
– does not exceed 2,1 times the rated current of the fuse-link, the circuit is not considered to
be adequately protected and the test is carried out with the fuse-link short-circuited;
– is at least 2,75 times the rated current of the fuse-link, the circuit is considered to be
adequately protected;
– is between 2,1 times and 2,75 times the rated current of the fuse-link, the fuse link is
short-circuited and the test is carried out
? for the relevant period or for 30 min, whichever is the shorter, for quick acting fuselinks;
? for the relevant period or for 2 min, whichever is the shorter, for time lag fuse-links.
NOTE 1 In case of doubt, the maximum resistance of the fuse-link has to be taken into account when determining
the current.
NOTE 2 The verification whether the fuse-link acts as a protective device is based on the fusing characteristics
specified in IEC 60127, which also gives the information necessary to calculate the maximum resistance of the
fuse-link.
NOTE 3 Other fuses are considered to be intentionally weak parts in accordance with 19.1.
分析方法如下：
1、 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；
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；
3、 测试和选择方法：
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；
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；
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）、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）。
4、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。
抛砖引玉，请高手完善。作者: ll123456 时间: 2011-12-27 11:47
为什么要除以2.75了？