During the tests of subclause 4.5.1 and 5.3, the temperatures of critical components shall be evaluated and shall be compared to their limiting values. For certain materials and components, the standard provides detailed instructions (e.g. in Table 4B, Table B.1, Table C.1) and for others only general compliance statements are provided (e.g. Note 3 of Table 4B part 2, subclause 5.3.8).
Optocouplers are often located in proximity to heat sources (e.g. transformers). The reliability of the materials used as insulator can degrade if thermally overstressed. IEC 60950-1 does not provide limit values for opto- couplers, nor does Annex P provide a reference to relevant component standards.
a: What are the limit values for optocouplers during normal operation of the EUT?
b: What are the limit values for optocouplers during fault operation of the EUT?
Temperature ratings as shown on the corresponding component certificate ( refer to “Explanatory Notes” below for the relevant component standards) shall be taken as limit values. For optocouplers bridging safety isolation, the maximum temperature Ts shall not be exceeded during normal operation.
Additional information from IEC TC 108:
The requirements for optocouplers during fault testing are considered adequately covered by subclauses 188.8.131.52 and 184.108.40.206 of the standard. There was no intention by TC108/MT2 that temperature measurements be applied to optocouplers during fault testing. TC108 does not support placing a minimum limit for Ts, such as the proposed 100 ℃, on optocouplers for either normal or fault operation.
来自 IEC TC 108的附加信息：
标准220.127.116.11和18.104.22.168条款充分涵盖了故障试验对光电耦合器的要求。TC108/MT2 无意在故障试验中测量光电耦合器温度。TC108 不支持在正常或故障状态时对光电耦合器设置有关Ts的最小限制。
As can be seen from examples 2 and 6 of IEC 60664-1 sub clause 4.2 corners with angles greater or equal than 90 degrees are not bridged. IEC 60664-1 does not contain specific information at which angle less than 90 degrees bridging shall be applied. Some of the above mentioned standards specify that bridging shall be applied for angles less than 80 degrees.
Can this 80 degree rule be applied in general for all standards?
Yes. The 80 degree rule shall be applied in general for all standards.
从 IEC 60664-1的4.2条款示例2和6中可以看出，角度大于或等于90度的角没有被桥接。IEC 60664-1不包含小于90度桥接角度的特定信息。很多标准提到，桥接应用于小于80度的角度。