琥珀流云 发表于 2010-8-9 09:35

每个人说法都不一样 我还是不清楚到底怎么做才是准确的

平凡 发表于 2011-7-20 12:11

引用第9楼狼行成双于2010-08-06 17:49发表的:
样机通电（空载），再短路（此时的电压就是异常条件下的开路电压），然后拉负载


我也是用以上的方法，此時的負載，一般是指二次測的負載，如通訊埠去拉載直流

以下為 無限流保護裝置的測法

2.5   LIMITED POWER SOURCE MEASUREMENTS

[]METHOD- Without An Overcurrent Protection Device -

A sample of the [ power supply ] [ transformer, Model ____________________ ] [ Operator Accessible Connector ] was connected to _____ [ V ac, _____ Hz ] [ V dc ].After each of the following output measurements, the values were compared with the Table 2B.

A.    The open circuit voltage (Uoc), with all load circuits disconnected.

B.    The output current (Isc) after [ ] 5 [ ] 60 seconds of operation with the load adjusted to maintain the Isc current limit (maximum Isc per Table 2B is 8.0 A or 150/Uoc, as applicable.See Notes to Lab.)Output circuits other than the circuit under test were unloaded during the Isc measurements.

C.    The maximum output Volt Ampere (VA), after [ ] 5 [ ] 60 seconds of operation with the load adjusted to maintain the VA limit (maximum VA per Table 2B is 100. (See Notes to Lab.)Output circuits other than the circuit under test were unloaded during the VA measurement.

(Note for A, B, C above: For product designs that require a small load in order to operate, the minimal load may be applied in order to measure the maximum output. The load used should be documented under “Comments.”)

[]    a linear or non-linear impedance limits the output in compliance with Table 2B.

[]    If a regulating network limited the output in compliance with Table 2B under normal operating conditions, then measurements (A), (B), and (C) were repeated under single fault conditions.The faults were placed in any part of the regulating network, including power supply pulse width modulation circuitry.

dkzenghaibo 发表于 2011-7-21 13:56

引用第1楼IEC60065于2010-07-30 16:29发表的:
我们先正常工作，然后再短路，调节加载电流。

我们也是这样。做的最多的就是适配器电源，通常LPS异常的结果要么是NORMAL 要么是shut down。NORMAL时空载电压是短路后去载看电压；电流就是一直往上加找到最大电流。
补充一点：做限功率电阻的时候我们通常是用锡线短路 带载，然后再通电看结果，一般会fuse open。

tjuking 发表于 2012-7-31 14:23

我的理解是限功率电阻其实是可以不必做短路试验的，因为UL datasheet上对于限功率电阻没有短路要求。对于regulating network，需要做短路实验，如果能分析出来限功率元器件，那直接断掉就可以，如果分析不出来，那就每个都得做。对于IC 限制电压或者电流的，如果不服和AnexxCC 需要做短路或者开路实验。
对于保护装置fuse 60s ，PTC 5s,需要短路以后再测一次。

cmk1991 发表于 2015-1-26 20:13

怎么判断电路里面的限流电阻？

弹指一挥uu 发表于 2015-2-27 14:47

琥珀流云 发表于 2010-8-6 14:32 static/image/common/back.gif
先正常工作??先带额定载吗? 然后短路后看到的电压就不是开路电压了~~~~

显然他的正常工作的意思是指正常通电，但是空载
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