IEC 60950 Ed. 2 (subclause 5.3.2)
IEC 60950, Ed. 3 (subclause 5.2.2)
IEC 60950-1, Ed. 2 (subclause 5.2.2)
Background:
In Japan, there is some confusion with the application of the Electric Strength Test in production (as routine test) to the finished equipment, in the scope of IEC 60950-1. Japanese IT industry believes that it is common practice widely performed in worldwide for several decades, to apply the electric strength test with the reduced duration between 1 s and 6 s, with the test voltage in accordance with Table 5B in IEC 60950-1.
Recently, however, another interpretation has been discussed in Japan that although the practice used to be authorized based on the statement in the note in clause 5.3.2 of IEC 60950:1991 (2nd edition), it is not allowed anymore after the release of IEC 60950:1999 (3rd edition) or later editions, because the note in clause 5.2.2 is stated differently than 2nd edition and there is no description specifying how the routine test should be done elsewhere in the standard.
The following is the comparison among three editions:
Note 1 in Clause 5.3.2. (IEC 60950:1991 2nd Ed.): For production test purpose, it is permitted to reduce the duration of electric strength test to 1 s.
Note 1 in Clause 5.2.2 (IEC 60950:1999 3rd Ed.): For ROUTINE TESTS specified elsewhere in this standard, it is permitted to reduce the duration of the electric strength test to 1 s.
In IEC 60950-1:2005 (2nd Edition) this text has been made normative and reads as follows: Where, elsewhere in this standard, ROUTINE TESTS are required to be conducted in accordance with 5.2.2, it is permitted to reduce the duration of the electric strength test to 1 s and to reduce the test voltage permitted in Table 5C, if used, by 10 %.
It is widely understood that the electric strength test time needs to be controlled to short duration, because if test voltage is applied for longer time, partial discharges may occur in solid insulation, and cause undetected insulation damage. This can result in unnecessary insulation failures during subsequent product use, and shorten the product's life span, as this does not only apply to internal parts and components, but also to the complete equipment.
Questions to the Panel:
1) Is it the intention of TC108 that the requirements of IEC 60950-1 clause 5.2.2 is to accept the application of the electric strength test in the production (routine test), to the equipment, (including components or material) reduced to 1 s or not?
2) Also, in case it is acceptable, if the test voltage should be in accordance to Table 5B in IEC 60950-1 or not?
Opinion of the Panel:
1) Yes
2) Yes
108/207/INF简要解析：
一般来说，抗电强度试验的持续时间要控制在较短的时间内，因为如果施加很长时间的高试验电压，会在固体绝缘中形成局部放电，造成未被发现的绝缘损坏。这可能导致产品在后续使用过程中出现不必要的绝缘故障，进而缩短产品寿命，这不仅针对内部部件，也影响了整个设备。TC108的意图是在生产过程的例行试验中，将抗电强度的持续时间缩短为1s，如果使用IEC 60950-1表5C的电压，还可以降低10%。
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