DSH 560A Temperature limits of optoelectronic devices used for separation
http://decisions.iecee.org/icons/ecblank.gif DSH 560A
Temperature limits of optoelectronic devices used for separation
1.5.2, 4.5.1, 5.3
60950-1(ed.1)
Question: During the tests of subclause 4.5.1 and 5.3, the temperatures of critical components shall beevaluated 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 relevantcomponent 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? Decision: 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 bysubclauses 5.3.9.1 and 5.3.9.2 of the standard. There was no intention by TC108/MT2 thattemperature measurements be applied to optocouplers during fault testing. TC108 does notsupport placing a minimum limit for Ts, such as the proposed 100 °C, on optocouplers for either normal or fault operation.
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